Endler Audio: Stepped Attenuators, Behringer 2496 Mods, Speaker Cables and Interconnects, Speakers

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Here is a compilation of comments I've made regarding various audio topics.

Some of these posts are getting very old and refer to topics that are now long gone in my progression but I will leave them here so that you won't have to take up where I have already abandoned.

This may be a little confusing without the other questions or anwers that originally accompanied these statements but you may still find them useful. You may find the original thread by searching for postings by user name sendler on the following boards:

Hard drive as music player. That is the opposite of what I have found regarding sound quality. The digital
out from my Hard drive/ FireWire410 sounds better into my dac than the digital
out of my EAD T1000 transport which had previously beaten all other transports I
had tried. Many of the dvd player's digital outs I tried sounded very poor.
Also, burns always sound better than the original cd depending on the blank that
was used and so is another reason to have your music on your pc. There are
numerous web sites set up to discuss this going back to 1999. No need to rehash
it here. Just my heart felt opinion. Add to this the sheer convenience of point
and click listening from a hard drive holding your entire music collection where
ever you may travel, and the advantages of having your music on a hard drive
become indisputable. For me, transports/ cd players have become obsolete.

PPS caps vs Dayton foil...I finally got around to trying the big hype PPS caps at 2uf as coupling for the direct out of my CS43122 dac. Depending who you read, the micro thin Polyphenylene Sulphide dielectric is heralded as a giant step forward in measured distortion and sound quality in the audio band.  I had high hopes for them due to the extremely small size which would allow a nice 7uf stack for the bass channels of my DCX mods but I am afraid the sonics fell slightly short of the Dayton foil which is so far in my experience unsurpassed in pristine clarity and tranparency of fine detail. They will trully spoil you from all other affordable caps for values up to 3.3uf. The PPS are pretty good though. Probably on par with most of the other metalized film caps I have tried at a fraction of the size but I will have to stick with the Dayton foils even if they are huge due to their 400v rating.
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http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PCF1132CT-ND
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http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-458

Listening for the best attenuator load for direct out AKM and CS dac chips I have been using direct stepped attenuators which plug onto the amps inputs as volume controls for 10 years and have been recommending a 4k fixed series/ switched shunt style for amps with input impedances up to 100k. Over 100k amps can consider a 20k attenuator to ease the load on the source. The 4k attenuators have the minimum interaction with any cabling and amp circuitry that follows them and are still well tolerated by most active outputs of the source equipment that will be feeding them barring the occasional high output impedance tube circuit. My digital source for the last 6 years has been a modified DEQ2496 running an AKM4395 dac chip direct out with no filters or active buffers. I have tried many different active opamp outputs but have found that just running the dac direct from the analog ouputs through a good cap or transformer to block the dc provides the most transparent sound as is discussed in many different threads about the AKM and also the CS dac chips.
It wasn't until I started playing with the transformers that I noticed that the cap out system still sounded better at louder attenuator settings but the trannies sounded better at quieter settings.    At -2db the attenuators provide a 21k load but this drops rapidly towards 4k at the middle and quieter settings. Was the single leg cap output stuggling with the now 4k impedance whereas the transformers, which use both output legs, had more power to drive it? This, and the observation that the lowish direct output level allows for a gain matched system using only small amounts of digital attenuation in the 0 to -12db range to trim full on reference listening levels with no analog volume control, which sounds even better due to the elimination of the series resistor which is always in the signal with the shunt type, has prompted me to consider changing to a ladder type attenuator. I have resisted a ladder until now due to the doubling of the cost per step but now see it as the ideal way to provide the optimum and constant load for the new crop of direct out dacs and still offer a straight through setting for digital volume control. Time for a redesign. But what is the ideal trade off between series (output) impedance and load?
In order to find the best sounding balance of load versus output impedance, I built a pair of ladder direct attenuators where each step had the same -6db attenuation, but different input impedances from 5k to 30k in 6 steps. It turned out to be a really fun project as I was able to get everything built without ordering any new parts. I originally would have liked to listen at -2db but a -6db level made finding the resistors easy as this is half and half, meaning that both legs of the L pad use the same resitance value. No formulas to bother with, all I had to do was grab a pair of resistors at half the desired input impedance for each setting of 5, 10, 15, 20, 25, and 30k. I was able to cut a couple traces on the boards I have been using to change them from shunt to ladder. The cheap but excellent Lorlin switches came apart with no fuss to rob an extra wiper, creating a two pole switch of sorts. Just what I needed. I was so stoked when that came together easily without having to order new parts. I started listening with my modified Sure 2X100 amp set up with input gain setting resistors of 150k:150k (virtual 150k? load) in order to minimize the interaction here (they sound better than 20k: 20k for some reason too, even with the terminating resistor preceding them), and a 20k input terminating resistor. I broke out some 8 foot speaker cables so the amp with the attenators on it could sit right in front of me on the coffee table. The attenuators allowed me to switch on the fly without moving from the listening position which made everything go pretty quickly. I let them break in for about 1/2 hour on each setting and then got right to listening. The difference was a little less than I expected but still worth the trouble in order to dial in the values of a new attenuator design. The AKM chip sounded best between 15k and 20k even into the 20k amp. This is the beauty of not having any cable following your passive volume control. Minimal interactions. I find that the most revealing aspect of music that can really sort out miniscule differences is in the decay of the reverb and recorded ambience and this was best at 15k. There was also an improvement in the body and weight of the images that interestingly faded toward the same type of increasing opacity toward both extremes of the attenuator. The CS43122 chip was also best at around 15k and maybe shading more toward the 10k side than 20k. I was also surprised that the transformers liked the 15k value the same as the caps.
Next I exchanged the 20k amp input termination that I had installed as it sounded better than 100k when running without a volume control. The chips do enjoy some load. I went back up to 100k resistors to further eliminate the interaction with the varying output impedance of the attenuator. This sounds much better! Just what I have been missing. Let the volume control be the entire amp input termination. Surprisingly again, both chips still sounded best into 15k even though the higher ouput impedance of the 25 and 30k settings was now more of a non issue with the increased amp input impedance. So 15k ladder it is. 10k may be a little better at quieter, -20 to -30db levels if that is where your system ends up but the Tripath amps I now find to sound the best can run with a wide range of gains as long as you also scale the supply voltage so I should always be able set my gain stucture to play a little too loud at -0db.

New ladder attenuator?   I can run my AK4395 and CS43122 dacs with transformer or cap coupled direct out and change back and forth just by moving the interconnects. This has allowed me to discover that with both legs of the dac contributing through the trannies in a balanced to single ended conversion, they have enough power to drive my 4k direct attenuators much better. One leg out through the caps sounds slightly closed in by comparison into the 4k load the attenuators provide at quieter settings. At louder settings, say -2db, the attenuators input impedance is 20.4k. At this load the beauty of the caps can sound better and are much cheaper than the transformers. The AKM chip happens to have the perfect level to connect straight to the Sure 2X100 with no volume control. This arrangement reveals that the Dayton foil caps do sound better than the best transformers but only if the load is eased to 10-20k at which point, digital volume control in the range of 0 to -12db sounds better than having any value of added series resistance of any style of analog volume control which would favor the availability of a straight through setting available with a ladder. Which is not to say that you can use a control with 20k in series with the signal in order to ease the load. I also have 20k series/ switched shunt direct attenuators. I changed the input terminating resistors and gain setting resistors R14,34,11,32,30,16 in an amp to 150k in order to compare 4k versus 20k attenuators and still maintain a suitable 7:1 ratio. I found that the 4k series resistor allowed more of the fine detail through. These are direct attenuators that plug right onto the amp's input connectors. The difference would be much greater if there were any length of interconnect involved, favoring the 4k value further. So where does this leave us? Since the direct out dacs are much cheaper to run with one leg through caps and have a lowish level that needs to be run nearly wide open through a terminating load no lower than 10k, I have decided start work on a new ladder type attenuator. Ladders cost twice as much per step but do have a sonic advantage over shunt types, of reduced series (output) impedance in the wide open ranges from 0 to -12db that I now need. I have never tried the current crop of series attenuators which can duplicate a ladder with one deck, due to the massive number of solder joints they introduce into the circuit but I guess I should also explore these as I have learned over the years, and more so with everything new I experiment with, you never know what something will sound like based on theory, until you listen to it. It is possible they could sound ok at wide open settings which would place most of the solder on the ground side. So I need to find out what the minimum value that sounds good with the direct out AKM is ( the CS chips have slightly more level and power so should be less fussy) and pick between ladder and series. Whatever I build next will use the excellent and affordable Susumu surface mount resistors as they sound better than any through hole resistors in this critical application.

Favorite music.  
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Anthriel has some great writing and playing
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The new SubSignal cd has some great vocal harmonies, great songs. Easy to listen to for your friends who are prog-metal "beginners".
Amazon.com: Beautiful & Monstrous: SUBSIGNAL: Music
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Other current favorites include:
Darkwater
Amazon.com: Calling The Earth to Witness: Darkwater: Music
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Suspyre
Amazon.com: When Time Fades: Suspyre: Music
.
Astra
Amazon.com: From Within: Astra: Music
.
Circus Maximus
Amazon.com: Isolate: Circus Maximus: Music
Aspera
Amazon.com: Ripples: Aspera: Music
.
Shadow Gallery
Amazon.com: Digital Ghosts: Shadow Gallery: Music
.
Silent Memorial
Amazon.com: Retrospective: Silent Memorial: Music
.
Status Minor
http://www.amazon.com/Dialog-Status-...1184839&sr=1-1
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Seventh Wonder
Amazon.com: Mercy Falls: Seventh Wonder: Music
.
Dream Theater
Amazon.com: Black Clouds & Silver Linings (3 CD Special Edition):…
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Dreamscape
Amazon.com: End of Silence: Dreamscape: Music
.
James LaBrie
Amazon.com: Elements of Persuasion: James Labrie: Music
.
Mind's Eye
Amazon.com: A Gentleman's Hurricane: Mind's Eye: Music
.
Pagan's Mind
Amazon.com: Enigmatic: Calling: Pagan's Mind: Music
.
Symphony X
http://www.amazon.com/V-Mythology-Su...1186386&sr=1-1
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Rush
Amazon.com: Power Windows: Rush: Music
.
Other favorites also include:
Flaw
Amazon.com: Endangered Species: Flaw: Music
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Catherine Wheel
http://www.amazon.com/Happy-Days-Cat...1186853&sr=1-7
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Megadeth
Amazon.com: Countdown to Extinction: Megadeth: Music
.
Extreme
Amazon.com: Waiting for the Punchline: Extreme: Music
.
Fuel
Amazon.com: Something Like Human: Fuel: Music
.
Tool
Amazon.com: Lateralus: Tool: Music
.
Taproot
Amazon.com: Blue Sky Research (Mcup): Taproot: Music
.
From Zero
Amazon.com: One Nation Under: From Zero: Music
.
Sevendust
Amazon.com: Home: Sevendust: Music
.
Queensryche
Amazon.com: Operation: Mindcrime: Queensryche: Music
.
Metallica
Amazon.com: Metallica: Metallica: Music
.
Stone Sour
Amazon.com: Come Whatever May: Stone Sour: Music
.
Alter Bridge
Amazon.com: Alter Bridge Blackbird Cd+dvd ( Exclusive Edition ): alter bridge: Music
.
Diffuser
Amazon.com: Injury Loves Melody: Diffuser: Music
.
Verve Pipe
Amazon.com: Pop Smear: Verve Pipe: Music
.
Kim Mitchell
Amazon.com: Universal Juveniles: Max Webster featuring Kim Mitchell: Music
.
Ian Anderson
Amazon.com: Secret Language of Birds: Ian Anderson: Music
.
Kings X
Amazon.com: King's X: King's X: Music
.
Freak Kitchen
http://www.amazon.com/Land-Freaks-Fr...1188998&sr=1-1
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Jethro Tull (You've got to be kidding me! This cd doesn't come up until the third Tull page on Amazon? Nobody likes this album?)
Amazon.com: Roots to Branches: Jethro Tull: Music
.
Jane's Addiction
Amazon.com: Strays: Jane's Addiction: Music
.
Incubus
Amazon.com: Make Yourself: Incubus: Music
.
Hoobastank
Amazon.com: Hoobastank: Hoobastank: Music
.
Mudvayne
Amazon.com: Mudvayne: Live Dosage 50 - Live in Peoria: Mudvayne, Phil Tuckett…
.
VanHalen
Amazon.com: Fair Warning: Van Halen: Music
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Gravity Kills
http://www.amazon.com/Gravity-Kills/...1190045&sr=8-1
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God Lives Underwater
Amazon.com: Empty: God Lives Underwater: Music
.
Soundgarden
Amazon.com: Badmotorfinger: Soundgarden: Music
.
Alice In Chains
Amazon.com: Dirt: Alice in Chains: Music
.
Stretch Princess
Amazon.com: Stretch Princess: Stretch Princess: Music
.
Heart
Amazon.com: Dog & Butterfly [ORIGINAL RECORDING REMASTERED] [EXTRA TRACKS]: Heart: Music
.
Tonic
Amazon.com: Lemon Parade: Tonic: Music
.
Veruca Salt
Amazon.com: Eight Arms to Hold You: Veruca Salt: Music
.
Aerosmith
Amazon.com: Toys in the Attic: Aerosmith: Music
.
K's Choice
Amazon.com: Paradise in Me: K's Choice: Music
.
Naked
Amazon.com: Naked: Naked: Music
.
Drain STH
Amazon.com: Horror Wrestling: Drain Sth: Music
.
Temple Of The Dog
Amazon.com: Temple of the Dog: Temple of the Dog: Music
.
Living Color
Amazon.com: Time's Up: Living Colour: Music
.
Judas Priest
Amazon.com: Free for All: Ted Nugent: Music
.
Steely Dan
http://www.amazon.com/Definitive-Col...1195258&sr=1-1
.

Unfortunately, the momentum of discussion always shifts to the "All (fill in the blank) sounds the same" crowd. I feel sorry for the newbies to the hobby that constantly get their brains washed over by this. Listening is still more sensitive than measurement. The hatred of sighted listening was built up in the 90's to challenge the dishonest marketing of the swelling High End. And rightly so. The price gouging is ridiculous. Now, the internet is mature and we have diy as a great alternative to High End Audio. It is time to let up on the constant hammering of the subjectivists that contribute freely all over these forums with nothing financial to gain.

Too busy to write.   Here are some threads I am writing in. Search for posts by sendler.
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Transformers...I listened to the cheapest high nickel Jensen transformers today. JT-11-YMPC. They really sound quite good despite their smallish size. Surprisingly, I didn't really hear any great deficiency or coloration in the bass. Compared to the FMCF, the sound stage was deep, slightly narrower for some reason but not worse. Just different. Image focus was actually a little tighter and better defined and sibilants were crisper with less smear. Maybe due to the Belden 1701a solid core in teflon bonded pair wire I used to hook them up versus the really small gauge stranded wire that comes stock on the FMs. I started out with solo female singer/guitar to evaluate them without a lot of power in the bass to get an idea about their use in the mids and highs of a DCX or soundcard crossover mod since they are cheaper when needing 6-8 channels and was about to proclaim them more than suitable until I put on something with a strong snare drum which seems to be a good signal to test the level handling of transformers. It was the crack of the snare/ cymbal that showed me the clear superiority of the EMCF over the FM and again showed up a further slight loss of dynamics in the YM. $50 each shipped right now on ebay for used JT-11 EMCF is a pretty good deal for a great transformer for direct out dac mods.

Amps.  
I have tried quite a few different diy amps. TDA7294, Behringer A500, Rega Delta 290, Velleman 50watt module with TIP147, original AKSA, single 3886, Bridged/balanced 3875 BA100, Ucd180, and the previous champ, TDA7250 driving TIPs. In that order of increasing sonic performance. By the time you get back to the A500 it is very disappointing. The 7250 was quite a step ahead of the rest although the BA100 showed how much better the 3875 can be with more chips if you have a balanced source such as my direct out DEQ2496. For chip amps, I would consider a BPA200 a minimum that might get you into the ball park if you have a nice balanced source to feed it with so you don't need a phase splitter on the input. A modified Sure 2X100 with a cheap smps beats them all. At a lower price. As long as you can get by with a powerful sounding 70 watts. Explosive dynamics and very transparent. I don't build any class A or tubes but have read from another guy with a KSA50 clone and an Aleph that his unmodified classD audio amp sounds better. Most people think of the little Tamp running on 12V when they talk about Class D but the newer, more powerful Class D can be quite impressive when run with a wide open output filter.
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Shunt vs. Ladder vs. Series attenuators...Yes, I run a Behringer DEQ or DCX2496 direct from the dac, out through a coupling cap as does DrVega. Panomaniac prefers transformers but it gets expensive with 6 in a DCX. My attenuators are fixed series 4k with a switched shunt. This allows an attenuator to be built with only 1 switch deck. A series attenuator uses 1 deck but has 12-24 solder joints and resistors in the path compared to only 2 for ladder or shunt . Ladder types seem to have technical advantages until you think it through. A 10k ladder is an easier load for the source at quieter levels although I have been reading that measured performance of the dac chip can actually improve when loaded with 3k. The sonic challenge for a passive volume control is the high output impedance which is, in effect a restriction in current that would be useful to drive the signal through the R, C, and L of the following cables and input stages of the amp. E.E. type theorists that don't believe in listening insist that these values are so low in any reasonable cable length so as to be ignored, but thousands of reports of listening tests by people drawn to the cheap price and purity of passives show mixed results when replacing an active volume control due to the increased interactions with a passive. The two keys to getting superior sonics along with the cheaper costs of passive are in choosing the lowest possible output impedance that your source will still drive, and minimizing the the cable length that follows the attenuator. Now, back to ladder vs. shunt. A 10k ladder (or series, or pot) has 10k input at all settings but the output impedance will change from 0 at full volume to 6.6k at -12db to 8k at -18db and continue to rise at quieter levels. The shunt style has a 4k output at all levels and the input is 20k at -2db dropping through 4.6k by -18db. But the 4k actually has a lower output impedance than the 10k series (pot) or ladder from -5db and quieter where most controls end up getting used, staying at 4k while the others are rising.
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2 feet cables seem short but in my experience, you will still hear them robbing you slightly. If aesthetics and convenience are secondary to getting the best sonics, I would recommend mounting the volume controls to the boards in the empty spot between the connectors and the heat sink. Or at least hardwiring from a housing front panel to the amp to keep the wires to 6 inches.

Listening vs. measurements...
Stereophile: A Transport of Delight: CD Transport Jitter
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I have recently been criticized for stating that I hear substantial differences between digital cables and transports so when I stumbled across this article showing the measured jitter of several transports and cables, I wanted to post the link to show an example of OBJECTIVE data that supports my (and hundreds of other individual's that get tired of arguing with people that don't trust their ears and only believe charts and graphs) listening experience. This article, which dates back to '93, is actually very old in the progression of our understanding of digital audio so I am sure that newer and more definitive measurements exist, but this will get the discussion started and help to keep some newbies from automatically falling in with the over bearing everything sounds "The Same" crowd.
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I don't have any hope of converting the legions of institutionalized engineers who only measure and seldom listen, who always jump in with greater numbers to squash any subjective discussion, but offer this as an example, not just for digital but in general for every different component right down to resistors caps and wire, to any newbies and other still open minded people trying to climb back over the fence, that sighted listening comparisons should not be automatically dismissed and can often push forward the need for new measurement techniques. Digital audio existed under the "Perfect Sound Forever" banner for ten years before the concept of jitter and the hardware to measure it became widely known as a result of a search for an objective explanation for differences that were noted in listening. We are getting closer but skilled listening on a cutting edge system can still be several orders of magnitude more sensitive than the best measurements, especially in the time domain.

Behringer SRC2496, DEQ in front of a DCX....
I use a  Behringer SRC2496 and a DEQ in front of my DCX in a digital chain. Well actually, I'm in between active cross projects for the last couple years while I have been working on developing various diy amplifiers which is easier when running my speakers with the passive crossover, so I have been using the direct out modified DEQ as my digital source but the SRC is useful in front of the DCX as well.  Since I run my main volume control at the amps and the modified DEQ/DCX doesn't have the high gain problems of the stock units, I like the SRC2496 for analog in as it has a level control that the other units lack so as to accept the analog from the source with no preamp and properly saturate the ADCs into full resolution. I have switched to internet radio and don't play my turntable much anymore so the analog in isn't used much, only for tv once in a while or if somebody wants to play something off of their phone. I normally play all my music from the digital out of a laptop/ M-Audio FireWire 410 digital in to the SRC for upsampling and then digital out. The upsampling actually works wonders with the DEQ, with 24/88.2 sounding noticeably deeper and more delicate. Better than 24/96 for some reason and much better than the straight,"external clock" pass through setting with either the 410 or my EAD T1000 transport. With the DCX, the differences that the SRC make with digital in are smaller and seem to favor the 24/96 over the 88.2 and the pass through only slightly but for the price it is a very cool piece of gear and looks super trick sitting under the DEQ and DCX in a stack! I have found some really transparent, cheap, digital cable, the twisted pairs pulled from Belden 1701A, to make my digital cables out of, so there is no draw back to running the digital stack. It's only a few bucks for the cables. The DEQ makes putting the final dashes of room EQ into your active cross (or passive cross) so much easier with it's graphic EQ and you may even find that you like a little stereo widening/balance and dynamic expansion. For some reason, many DCX users take offense to the mention of the DEQ as being redundant but I find the graphic EQ more intuitive for fine adjustments. The SRC2496 also has a decent headphone amp built in which I use at night and would be worth most of the cost by it's self.

AK4395 vs. AK4396 listening comparisons...The AK4396 has been around for a couple of years now and I have had a lot of people asking me about it as a possible upgrade to the AK4393 that comes stock in the Behringer 2496 audio gear but I have just now been able to get my US distributor to supply them. I installed an AK4396 dac chip in a direct out modified DEQ in order to compare it with the AK4395 that I have been recommending. The 4396 drops in to the board space vacated by the AK4393 and works fine on 3.3v with no other mods whereas the 4395 needs an extra regulator to provide 5v to pin 2, assuming that you don’t want to share the analog 5v with the digital pin. It’s interesting that the two chips do sound quite different. Although I usually have little trouble picking one component I like best from listening trials, it has been very difficult for me to choose a clear winner this time. These chips both offer stratospheric performance. It’s funny that I actually started to feel some pressure from my indecision. I also swapped the boards into the opposite chassis to make sure that I was minimizing the variables and tried both 4k and 20k stepped attenuators even though the 20k attenuators don’t work as well with my 22k amps.  The 4396 has a more powerful sound even working into my 4k stepped attenuators despite it’s lower stated power consumption. It throws it’s soundstage closer to the listener, more toward the front line of the speakers and actually plays about 1db louder depending on the program material. The 4395’s bass was heard to extend much further than the stock 4393’s, along with a big improvement in resolving ability, and the 4396 has just as much extension, with a higher level, up into the mid bass. This makes the 4395 sound a bit lean in comparison. On the other hand, the 4395 throws it’s sound stage much deeper, starting just behind the plane of the speakers and going back beyond the front wall of the room. The 4396’s stage is pleasantly a bit taller. The 96 lights the stage more brightly, making each instrument stand apart from the others but lacks the ultimate resolution of the 95’s ability to follow the sounds right to the fine end. Some tracks favor the 4396’s closer presentation as feeling more involving and easier to follow. On other cuts I preferred the 4395’s extra ability to resolve reverberation tails and ambient information, making the 96 feel like it is leaving something behind. So the trade offs went back and forth causing one of those listening binges where you just keep pulling one cd after another off of the shelf, and can’t wait to get home the next day to do it all over again. At this point, with my current associated equipment, I will have to choose the AK4395 for it’s extra resolving ability even though I was hoping the 4396’s more focused and powerful sound would win as it would be easier to install. With different equipment I can see where this might go the other way so I will check back on the 4396 as things in my system change.

New DAC chip upgrade to AK4395...AK4395 Dac swap is now included in the pricing for the direct out mods.      I finally took the time to develop the circuit mod that the AK4395
needs in order to supply it's 5v ( the 4393 uses 3.3v). It turned out
to be a very straight forward matter of adding another voltage
regulator. The new chip is unbelievable! It adds another quantum leap
in sonics to the one that the direct out accomplishes. The sound stage
is wider, deeper and taller, with a blacker background. Dynamics and
bass slam are an incredible improvement. Air and acoustic decay are
increased in fine detail giving the instruments a more realistic and
musical presentation. I have always liked AK4395 but had put it on the
back burner for years because it seemed that it would need an all new
board to make it more reliable as it was finniky when running on 3.3v.
Now I find that all that was need was to lift pin 2 and supply a
dedicated 5v. The sound is so much better! I am Psyched! Whereas the
4393 benefited from a slight amount of ultrasonic filtering, The AK4395
sounds incredible running straight out to the coupling cap with no filter, eliminating the last few components in the way of the most pure sound I have ever
heard at any price.

Digital cables make a big diference...I use my SRC in front of the DEQ for upsampling and the input level control for analog sources that the DEQ lacks. My DEQ (and DCX) has the direct out mod which gives an analog out that smokes the likes of the DAC1. Digital cables make as much or more difference than analog cables in my system. I was actually doing some listening tests with some new digital cable last weekend and I can even hear a difference between pairs of the exact same solid core in teflon pairs with a different twist rate. A toslink from the SRC to the DEQ sounds surprisingly good. $15.00 RadioShack gold optical. Very close to my best DIY digital interconnect running balanced which surpasses the high value Apogee cables. I tried a Hosa digital balanced cable but sent it back as it sounded so bad.

Mine is not to question why...   I don't know why digital cables sound different. Probably for the same reasons analog cables sound different. And caps sound different. Skin effect? Dielectric absorbsion? Strand interaction? I just listen to different things and keep the best ones. Who cares about what SHOULD BE after you find out what IS.

 

Mod listening tests

News Flash...

The new DAC chip sounds best with no filter or output resistor at all. Nothing but the necessary foil coupling cap between you and your music.

But here is the test of the earlier mod with filter.

Ultrasonic filter listening tests... I have done some listening tests with easier load filters in the direct out mod and have settled on a 12db filter at 91Khz with a total series resistance of 370 ohms. I tried total output resistances as high as 740 but found that the sound quality was fading fast. Values that high would necessitate short cables to an active buffer/volume control. Compared to the 6db/octave filter at 45khz, the 12db filter is more fully extended in the highs and is definitely the way to go. With 370 ohms added to the output impedence of the circuit, the presentation isn't quite as liquid or fleshed out as with the 36 ohm set up but is still exceptional in this regard and actually takes on a more pristine quality in the highs. After listening to the new filter, cymbal crashes with the early filter had a slight roughness around them, probably owing to some audibility of the added distortion from the heavy load. On the other end of the trials with 740 ohms in series, The sound was noticably washed out. Detail and reverberant decay suffered badly. Impact was robbed, sounding as if a layer of cardboard had been laid over the snare. leading edge definition of bass and kick drum was wiped away leaving a marshmallowy texture to the attack. I found some nice Wima foil over polypro caps for the filter but have yet to try them in place of the foil and polystyrene orange drops that I have been using. I also ran some comparisons for the coupling caps with a stack of Dayton .47uf foils easily beating out a bypassed Dayton polypro and edging a 5 to 1 foil bypassed Clarity cap. The Dayton foil caps are the champs for see through detail. An Audiocap Theta could be used but would cost twice as much and wouldn't fit under the hood as well as the stacks of Daytons.

Opamp distortion tests.

http://www.sg-acoustics.ch/analogue_audio/ic_opamps/pdf/opamp_distortion.pdf

Great article. Especially for any one considering active crossovers such as the Orion. It is interesting that the tests don't favor my favorite, the LT1360. I have evaluated Burr Brown OPA134 (Over hyped de facto opamp in high end audio equipment. Not nearly as transparent as the LT.)and OPA627 (much better but not quite as good as the LT, a little distant and not as dynamic, and way over priced), Analog Devices AD811 (very good. Warmer than LT but too fussy about power supply design) and my absolute favorite, The LT1360 (Explosive and transparent) which sounds very close to the AD811 and has proven to be indestructable. The real, not surprising loser, is the OPA604 which must have gotten some good marketing because it has seen quite a lot of use in high end source equipment but is well known to be upgraded by the 134.

I have compared all the previously mentioned opamps in various applications. Output driver, unity buffer, gain stage at 6-18db, I/V converter, dc servo, inverting stage, differential amp, etc. The sonics of the LT1360 are in general the best. Several steps ahead of the OPA134. Why the LT13xx family isn't more popular I have no idea. I have been raving about them for years. They drop into any application and sound better than whatever you took out and stand up to incredible miss use. The AD amps sound very good as well but are very fussy about implimentation, I have had two of them fail, and somewhat pricier so I have given up on them. I don't find much advantage to the even faster 1364 so I just prefer to play it safe and stick to the 1360/1361. The 134 is a good amp and will be a nice step up from the TL071 that was ubiquitous in the 80's ( A great invention in it's day but is now a dinosaur, very opaqe in comparison. Responsible for the bad rap opamps get that lingers to this day.) but I find the 1360 sounds more open and see through. These studies are now 5 years old so there are some newer amps that I should try such as the AD797.

Six knobs...Six knobs that click aren't any harder to adjust than one knob. Click, click, click, click, click, click, vs. turn. The difference is about the same amount of time that it took to read that sentence. If you are going to give up remote control then the real consideration is walking over to the amps. After you are there, turning one knob or six is not that much different. Six knobs (or even three) that don't have matched steps would be very difficult to get repeatable settings, however. With the stepped attenuators it is easy to get any volume that you want and keep all of the channels perfectly matched. The real question is to remote or not to remote and comes down to how much emphasis is to be placed on sound quality vs. convenience. When the payoff is this great, I will chose sound quality every time.

Room treatment.....Room treatment is very important and one of the most cost effective upgrades you can make to your audio system. Carpeting or rugs are something that any "interior decorator" can be talked into. Speaker placement should be considered as they will sound much better if placed out from the front wall. My room is 16' by 14' by 8.5' and my tweeters are out 53" from the front wall on solid stands. If you can't leave them that far out into the room then place a small mark into the carpet with a piece of masking tape or something so that you can move them back into position for serious listening sessions. My listeng position also places my ears out from the back wall 39". Again, you can move things into better position for listening if you can't leave them for the best sound all of the time. Move around and listen for the best sound. Wall treatments are more difficult to sell to the "decorator" but are crucial to the best sound. Heavy quilts don't cost that much and can be chosen to add to the decor. Heavy draperies work well also. The key places are in the corners behind the speakers and at the first reflection point of the sidewalls. I use a queen size quilt for each and one on the wall behind me. Sit in the listeng position and have a helper hold a hand mirror aganst the walls in various places. Wherever you see the speakers in the mirror is a reflection point. It is possible to use too much absorbtion. I actually tried some absorbtion on the ceiling at the reflection point and over the video monitor which is between the speakers but removed it as it didn't improve the clarity at all and only served to rob some of the impact from the bass. For the final touch on absorbtion, treat all four corners of the ceiling with pieces of acoustic foam cut to fit about 18" of the xyz axiss of the ceiling/walls. Your new room will sound much more detailed and quicker for music and even in conversation.

Digital volume. The first analog to digital conversion will sound best if the meters show a full signal level. If the signal is low on the meters you are throwing away resolution as the digital word is written with zeros filling in the missing signal level. The same thing happens in a digital volume control which works by throwing away the quieter nuances in the signal and shifting the louder, more obvious parts, down the word into the vacated places and filling the rest in with zeros. I set the analog in level of my SRC by ear for each recording. Too loud and the sound begins to crackle, too quiet and it lacks detail. Once the signal is digital, it can still change in volume when it runs through an EQ. You may have to turn the level down in the utility screen of the DEQ to keep the sound from crackling.

Active cross signal chain.....The comparisons were done with the DEQ running digital in/out for EQ into the DCX or the Dac1. The DCX was used as 2 channel DAC. I could have used another DEQ (or the first one) instead of the DCX but didn't have the direct out mod in them at the time. The sonics of a modified DEQ or DCX will be about the same if preceded by an upsampler such as the SRC2496. Upsampling is a big improvement in a DAC that doesn't upsample (DEQ). I'm not sure why the current discussions seam to favor leaving the digital in at 44.1k. My experience shows improvements across the board when upsampling. A DAC that is already upsampling will show far less improvement with 96k vs. 44.1 but I don't hear any negatives. Anyway, the comparisons were done with the second version direct out mod which has been further improved in version 3. the latest mod involves swapping the DAC chips to the even better sounding AK4395 which sound fantastic running with no analog filter. A repeat comparison would be no contest favoring the modded Behringer gear. In your application, implimentation of an active cross system such as mine should be another step up, especially for your digital sources. The programming of the DCX is actually very easy to do by ear as you can vary the settings continuously and listen in real time to different crossover points and time alignments. The hardware count starts to add up but it is all so cheap by high end standards that a cutting edge digital active cross system can be done for a reasonable price if you already have some nice amps.The common mistake is running the sole volume control in front of the digital processing with no volume control after which leaves you with low digital words full of empty resolution. The trick is to have stepped volume control at the amps so you can keep the digital at max resolution at any listening level. From there, digital volume control to fine tune the listening level from song to song is ok. The ideal set up for you would be source (digital or analog)> SRC2496 (for upsampling or analog conversion)> digital cable > DEQ (for EQ, widening, dynamic expansion, ect) > digtal cable > DCX2496 (for crossover) > analog cables > stepped attenuators > amps > speakers. You don't need a preamp and the DCX or DEQ replaces your DAC but you will want to use a good digital transport such as a computer or cd player as with any DAC (many dvd players rewrite the digital audio out poorly, a few sound great).
.

Behringer 2496s Sound Great.....The Behringer DCX2496 sounds great, especially running digital in so as not to add another set of D to A - A to D conversions. I sold my DBX DriveRack PA after getting into the Behringer 2496 gear as the later sounds much better, in part because of the lack of a digital in with the DBX. For the DIYer, digital cross is the way to go as long as you are willing to keep the same quality of amplifiers in triple. Because of this, digital cross will be more expensive in the short run but, if you are the type to try a few different designs and drivers from year to year it is actually more convenient. You can knock together a test cabinet and get a passive beating digital crover set up by ear in an hour. From there if want, you can use measurements to dial in an even better text book tranfer function for each driver but this isn't even necessary as the sound will already be better than the passive cross would because eliminating the passive components is a clearer window to the sound. For ultimate sound quality the DCX also has an advantage over passive cross. Tri amping a 3way will sound better than an identical single amp and the advantages of 3 versus 1 apply all the way back down the signal chain to the DAC chips where each channel is responsible for a smaller share of the signal so it can do a better job. Also, with the direct out mod, The Behringers will have better sound quality than multi thousand dollar high end DACs so even if you do chose to build a passive cross project or two, you will be happy to have a 2496 as a reference source. Behringer is a very dirty word to most pro audio guys so don't expect an unbiased opinion from them. There have been reliability issues and concerns for outright circuit theft from the big B (years ago as a fledgling start up company) but for home use, you can't touch the price/performance of the SRC, DEQ, and DCX2496. Check out the Yahoogroup for more info.
http://tech.groups.yahoo.com/group/DCX2496/

370 ohm filter, Aliasing, 2nd order slopes... (note.. The current version of the mod with AK4395 chip and no filter KILLS the sonics of the second version 370 ohm mod)...The original direct out mod of the DCX and DEQ2496 with 37ohms sounded way better than
stock, better than on the board mods, better than custom active,
better than multitapped transformers, even though there was some
increased distortion due to the ultrasonic load on the dac output.
The 370 ohm load of the new filter working through a corner frequncy
which is twice as high, sounds even better. You can not assume. You
have to try. This is the only way to find out.  I tried output
resistances as high as 720 ohms but the output impedance was getting
too high to sound good driving my 4k stepped attenuators, causing the
sound to thicken, roll off the top end, and steal the dynamics in the
bass. The 370 ohm filter working into two poles at 90khz will have
2000% less load in the audio band than the first filter which sounded
way better than stock as it was. If you want to run an active volume
control with >20k input impedance after the DCX the 1000 ohm filter
will work fine.
.
As to Aliasing.
The entire thread that developed about the passive filter causing
aliasing was very entertaining with all of the math presented and
everything but has NO place in the disscusion of ultrasonic noise
riding on an analog audio signal. Aliasing occurs when a digital
conversion is attempted on a signal which contains frequencies
greater than half of the sampling rate. This produces a new tone
(alias) back into the audio band, creating the need for the
infamous "brick wall digital filter". Aliasing is obviously totaly
unacceptable but can only be a concern prior to a conversion. The circuit in question comes after all conversions are complete so the concept of aliasing can not apply.
 It is
however, possible for the ultrasonic noise to intermodulate with the
program material, creating side bands back into the audio spectrum
but the overall level of noise created by the AKM dacs is much lower
than previous high end dac chips, with a maximum level which is
still -115db down from the full scale output. Any IM products
produced by the noise must obviously be even lower in level than the
impetus that created them. The noise is so low to begin with that
these dacs actually sound excellent running direct out with no
filter. I happen to find that the sound is a little more liquid and
musical with a filter but if you are having trouble deciding between
this and that, by all means, just run the direct out with no filter
to try it. To determine the effect of the ultra sonic noise on the
noise floor in the audio band and thereby compute the theoretical
loss of bits of resolution would require advanced measurements with
ultra low noise floor test equipment and ultra low level pure 24 bit
signals - and a decimal point in front of the theoretical bits lost
when all is said and done.
.
Textbook filter slopes
.
The fact that the two pole filter doesn't exhibit a textbook 2nd
order slope isn't important either. There is no high pass filter to
transfer to so it is not like the slope has to match anything. Being
so far out of the audio band, the shape of the slope or phase
tracking doesn't matter. It is just there to shunt ultrasonic noise.
If you want to work with a series coil, go ahead but I prefer not to
as the caps will work fine. If you want the best measured performance
then the stock unit will provide that but there are audible
improvements that may measure worse in various ways but sound much
better.

Regular cat5 sounds terrible..   I tried some regular cat5 from Home Depot for digital and it sounded terrible. Very opaque and slow like the Hosa digital cable that I sent back after finding out how bad it sounded. The BondedPair in Teflon 1701A is amazing as digital cable and very good as analog. For digital, one pair, no shield, ground lifted, sounds completely open and detailed. Single ended analog with all four pairs carrying plus and minus sounds explosive and see through yet still has enough body to stay musical. For Balanced analog I would use three pairs for hot and cold with the fourth for pins 1. I've tried other shielded coax such as the favorite 1506, and other scraps of rg types, for digital  and analog and have yet to hear any coax that was even close to acceptable.

Digital Cross   My Usher twoways have the crossover boards mounted externally so I can switch between the biamped analog cross (foil coils and foil bypassed Solens) and the digital cross from My DCX2496. Both systems run optimized EQs in a DEQ2496 to sound their best. The digital cross has more detail and transparency and the space between the instruments is blacker. There is more musical information to hear. The benefits of biamping also apply to bi-DACing. Share the work so that each has it easier.

My signal path runs transport-SRC2496-DEQ2496-DCX2496-Stepped Attenuators-Amps-Speaker Drivers. Too bad the SRC is no longer available. I don't know if you could get one used on ebay. If sound quality is paramount the stepped attenuators following the direct out mod of the DCX (orDEQ) will put the sonics in line with $3000.00 cd players and preamps. I am very surprised that I have had only two people with DCXs using them. This was the main reason that I decided to build them. But I have sold hundreds, Maybe close to one thousand, to two channel audiophiles with an average system price of $10,000.00 and have only had three pairs returned. Two of which were by guys with $8000.00 Wadia cd players which have an advanced onboard volume control. You have nothing to lose in trying the attenuators. If you don't like them for any reason, just send them back for a full refund. You will be out only 4-5 bucks for the return shipping.
.
.

EQ Adjustment...  Many people ask me how to adjust the eq and seem to make it out to be harder than it is. To adjust the eq I start with the highs. Shaker or castinets are very revealing of eq from 20k down to 6 or 7k. Next listen to guitars or piano while raising and lowering the levels of each band one at a time until they each sound right. Human voice is good from 3.5k down into the mid base. Just start with the highs and go down through the range of adjustments adjusting each band in turn until it sounds the best. Start quickly at first and repeat the procedure three or four times to zero in on the most natural sound.

Amps.    The sound quality of the Sziklai will have to make a noticeable improvement to justify the added expense as the TIP142/147 offer pretty amazing sound and value at their give away price and I see that Motorla makes theirs with higher specs that I will also have to try. The TDA7250 is the first amp that I ever built and I have been trying to surpass the sound ever since. Amps that I have tried in the order of preference are; Velleman K4005(TDA7250 with TIPs), Ucd180 (very good for the money at $85 assembled but can't mach the transparency of the TDA7250), Velleman K4010 (interesting old sliding bias scheme with lots of power but a little less detail still), Audio Source amp two( The best deal in a ready made amp that I have found), AKSA( nice conveyance of emotion but still less detail and power), Velleman VM100( Awsome deal for $50 assembled which includes a basic supply section on the board. Could be a giant killer if I can find out how to safely increase the bias to the degree of the TIPs in the 7250),3886 chips(over rated on the disscusion boards due the simplicity and availability of boards for DIY. Weak power, weak bass with middle of the pack detail.) 7294 ( very dissapointing.The VM100 kills it. Thick and stupid like all of the cheap home theater recievers that I have tried off of the used rack, including a $1000 Dennon. Behringer A500( a powerhouse but sonics are in line with the 7294 that I didn't like. I haven't tried a Pannasonic X yet though which I understand can be pretty good with a digital input.)I could try the Bi120 but it is a little out of my price range for true balanced, bridged in an active crossover from a DCX2496 which the 7250 is good at.
.

Transports and digital cables.   There are big differences between the sound quality of the digital outs of dvd players. Unfortunately, many dvd players use clumsy processing before sending the digital out so "the digital" in the cable isn't the same data. My Phillips sounds pretty bad. My cheap Sony sounds awesome, as good as my T1000 transport. There is a lot more going on in the digital realm than you might think. I find as much difference between digital cables as I do between analog cables. I sent the Hosa AES/EBU cables back as they sounded terrible. The popular Belden 1506A sounds terrible to me as well. Apogee WidEye is much better. DIY of Belden 1874A is the best. Optical interfaces have improved quite a bit as well and are now close to a good RCA digital cable. Here's another brain teaser, most burns sound better than the original. I don't have an X-Box but if you can round up a Sony NS500 I know that will sound about as good as it gets. The current and cheaper Sonys may be just as good.

Behringer A500 initial impressions. As more people, myself included, are using multiple channels of amplification for surround or active crossovers, I keep hoping that a cheap amp will emerge from the pro audio segment to fill the bill.
There is a shift in the pro companies to offer new amps with
convective cooling (no fan) and add copy suggesting an emphasise on
sound quality over brute power. Enter the Behringer A500. I am very
happy with the performance of my SRC/DEQ/DCX 2496 series digital
source components and so have been anxiously awaiting the the
arrival of the A500 since it's announcement last winter. The wait is
over and the new Behringer A500 is finally available at Music123 for
$179.00. The price is right and they offer a 45 day return policy so
I bought one to try. The amp is built well enough with massive
heatsinks and sturdy connectors. Power specs are good at 160 watts/8
ohms, 230 watts/4 ohms and 500 watts 8 ohms bridged with rca, xlr
and trs inputs. The front panel is plastic but very stylish ala the
Alesis amp. Behringer does alot of "ala" but I'm not going to make
that into my problem. Unfortunately, as I was with the the SLA1, I
am again dissapointed with the sound. Gain is quite plentiful with
the knobs normally at the one third position but the sonics are a
bit on the opaque side. Break in was with my tuner into dummy loads
for five days. I didn't take any notes on the listening impressions.
I didn't need to. Don't get me wrong. The sound is no worse than
some of the other mid fi amps that I've heard from Adcom and NAD,
and is still much better than the multi channel recievers in the
$1000.00 range, but in stock form it isn't going to replace any of
our high end amps. The torroid is huge with seperate secondaries for
right and left and there is plenty of room in the casework for mods
so there is still hope. If only I can get a schematic. Spliting the
legs to run true balanced/ briged should be a worthy external mod
requiring only a custom cable but I would need another A500 to try
that in stereo. Because of the roomy and stylish case (my stepped
attenuators will bolt right in), I haven't given up on this unit yet
so stay tuned for more info.
http://www.behringer.com/A500/index.cfm?lang=ENG

I like to use a graphic eq for final in room response tuning. I find this very easy compared to measuring and then building specific parametric eqs. Just slide the controls up and down until it sounds right. Running a DEQ2496, digital in-out, in front of your crossover is a very simple, powerful and transparent way to put the final touches on your sound

Most of the less than stellar reviews seem to come from users running analog in with the volume control before the DCX/DEQ which given the high pro audio output level means that for any normal listening volume level, you are using very few of the available bits in the analog to digital converters. Used this way, either unit will sound quite lacking in detail. Even running full level analog in, with the volume control after, introduces another set of ad/da conversions which in the best of circumstances can never be as transparent as the direct feed. The real beauty of these units is realized when running digital in. When used with a digital input and the volume controls after the Behringers, they offer sonics which will compare to hi end dacs of five+ times the price not to mention all the flexibility that drew our attention in the first place.

even though the active cross was done by ear with no pre crossover notch filtering ect. The digital crossover sounds way better than the passive cross on my Usher two ways. More detailed, see through and dynamic. Both active and passive cross versions were auditioned with the eq optimized for each with a DEQ preceding the DCX.

You can always try it passive first to see if you can hear any degradation. Whenever I split off an unbalanced feed I try to match the inpedance on the unused leg with a resistor to ground. The inputs of equipment are usually dc blocked with a cap so you will either have to measure the input impedance of the sub amp with a measurement system at the input connector or to get a close approximation of the impedence you can measure the resistance to ground just inside the blocking cap with an ohm meter. Use this value with a resistor from pin 3 to pin 1 of the adapter to the sub. Test by ear by listening to the monitors with the sub amp off or tuned down all the way and swapping the adapter in and out. Even if you lose the perfect balance in the legs to the monitors it doesn't mean the sound quality will suffer, only that the common mode noise rejection won't be as good and noise pickup in the home isn't a big deal anyway.

The digital in through the SRC doesn't "add" anything, just makes the sound a bit more pristine and dynamic, even though the DCX is apparently already upsampling to 96k in its own receiver chip.I haven't really compared the analog in of the SRC to the DCX but the SRC has an input level control for the analog making it infinitely better for DCX users with multichannel volume controls at the amps.

All other amps I've seen use 1 and 8. some use a divider splitting V- (everybody else) for offset nulling, some use V+ (Burr Brown). Most applications skip offset nulling but the out put of a PRE might be using it which means that you could have a conflict with the Burr Brown chips. If you omit offset nulling for your listening trials you can bend out pins 1,5 and 8 for no connection. This will allow you to try any single type of opamp. I have evaluated Burr Brown OPA134 (over rated)and OPA627 (much better but not quite as good as the LT and way over priced), Analog Devices AD811 (very good but too fussy about power supply design) and my absolute favorite, The LT1360 which sounds very close to the AD811 and has proven to be indestructable. Deffinitely use sockets and experiment for yourself. You can add a small trimming pot to the top of the opamp for DC offset nulling when you decide which one you like best.

I have compared all the previously mentioned opamps in various applications. Output driver, unity buffer, gain stage at 6-18db, I/V converter, dc servo, inverting stage, differential amp, etc. The sonics of the LT1360 are in general the best. Several steps ahead of the OPA134. Why the LT13xx family isn't more popular I have no idea. I have been raving about them for years. They drop into any application and sound better than whatever you took out and stand up to incredible miss use. The AD amps sound very good as well but are very fussy about implimentation and somewhat pricier so I have given up on them. I don't find much advantage to the even faster 1364 so I just prefer to play it safe and stick to the 1360/1361. The 134 is a good amp and will be a nice step up from the 071 but I find the 1360 sounds more open and see through.

Having gain controls on your amp will allow you to use the DEQ2496 between the pre and power amp as it is intended for pro use. In this case, you can set the pre as needed to get the best sound from the ADC and then set the loudest listening volume at the amp. You can then control the listening volume with the pre as usual without losing so much resolution.
 
I had the 1801b home for a trial and you will not want to sell your self short on power. They feature full baffle step compensation which knocks the efficiency down. They were much better when I biamped them for 140 watts than when running 70 watts in. I build my own amps so I can't make a recommendation other than for you to stay away from lowish powered amps with this speaker.
 
I eliminated my preamp with stepped attenuators at the amps and the sound is much better.
 
if you run analog in you need volume control before and after the DEQ to get adaquate saturation of the analog to digital converters otherwise resolution suffers if the incoming analog signal is less than peaking the meters. Pro amps have volume controls so this gives the second set of controls. For analog in at home I'll have to try the SRC2496 to see if the front panel volume knob can be configured to control the gain before the ADCs. If so, then analog users would want to use this unit in front of their DEQ. The SRC is worth having (only $130) for digital users anyway as the upsampler sounds excellent, giving the final layer of detail, dynamics and musicality.
 
Then you will want to fine tune the EQ by ear. Or just skip the mic and auto EQ tune by ear. The Behringer DEQ2496 sounds great and should be considered a must have product for any system running digital in.
 
The common thing to do is to just leave it cranked but it may actually give you better signal to noise ratios and lower distortion to turn the the preamp up into it's cleanest range and set the listening volume back down at the amp. Better yet, you should try connecting your source directly to the amp without the pre as this may sound even better.
 
Now that there are EQs that don't degrade the sound quality. You can't believe the difference 2db can make here and there.
 
The digital active crossover is way better than the tweaked and EQed passive cross of my Usher two-ways.
 
Yes, Just use coax to a cheap xlr to rca adapter. There is a menu selection to tell it that spdif is coming in on the aes/ebu (xlr) jack but it doesn't even matter which way you set it. The DEQ will lock to the incoming signal either way.
 
Especially after a long break in. The DEQ2496 easily replaced the Assemblage DAC2.7 as my reference Dac (Although now, with a few simple, albiet major mods, my DCX2496 is really giving great analog sound. It is too bad that most people on these boards try to dismiss this product based on it's heritage without really giving it a chance. Others actually chime in to the discussions rooting for a bad review without even hearing one. " see I new it, It's cheap and it's pro". The fact is that if you have a better sounding Dac, then you can use the digital out and have a convenient, transparent EQ. For me, analog out was a step up so I use it as well.
 
Amps with a good damping factor can handle any speaker. Even low impedance types such as the old apogee panels ect. You should consider your speaker options wide open. The only time damping factor becomes an issue is when you are dealing with an amp with a poor damping factor like a single ended triode with no feedback. These amps can have damping factors as low as 4 or 3 and are better suited to special speakers with higher impedances.
 
Damping factor is the ratio of the input impedance of the speaker vs the output impedance of the amp. the lower the output impedance of the amp (.1 ohms would be damping factor of 80), the easier it is for the needed current to flow out of it to control the speaker. The higher impedance tube amps (1 ohm for a damping factor of 8) will control the back emf of the speaker less well
 
Using the DEQ with a digital input is a no brainer given the price/performance. The sound quality for the analog in is where the debate starts as it really takes two sets of volume controls, one before the Behringer to set the perfect input level to get the most resolution from the analog to digital converters and one set of stepped attenuators or something after the DEQ to get at least coarse control of the listening volume.
 
The DEQ2496 can accept digital in from your transport or dvd player on aes/ebu, coax with a cheap adapter (this is how I use it) or toslink. If you have a really great Dac you can send digital out from the Behringer to it for the analog conversion. The analog outs of the DEQ sound better than my best Dac (Assemblage DAC2.7) so I send the analog out to stepped attenuators at my amps.
 
For digital sources, the new digital EQs such as the TacT and the more affordable new DEQ2496 from Behringer are very transparent when run with a digital in and offer room correction that will vastly improve any system.
I did have an Enlightened Audio Designs DSP1000 mk3 and a Monarchy 22A home at the same time to compare to my Assemblage and the DAC2.7 was much more refined and detailed than the EAD and the Monarchy. Compared to my modified Assemblage DAC2.7 the DEQ2496 is better. Wider, Taller and a touch warmer and more fully fleshed out. That is not to mention the digital eq which I will never live without again.
 
I have experience with that DAC and the Monarchy is very laid back, euphonic and veiled when compared with the newest cutting edge digital sources. I highly recommend the Behringer DEQ2496 as the best bang for the buck source right now. You get a great DAC AND a digital EQ for $250.
 
When used for fine tuning the volume while listening. The trick is to have another analog volume control in the system after the Dac for the major volume changes
 
I run digital in and digital out through a Behringer DEQ2496 in a similar set up and will never go without a digital eq again. The analog outs of the DCX don't sound quite as good as the DEQ for some reason so I'm still working on mods ( along with several other people that post at the Yahoo users group) for that. As far as going with a digital active crossover, I can tell you that it will sound way better than the passive crossover in a speaker as you share the work load into smaller frequency bands through the amps and all the way back through the dacs to the digital source. This is probably overkill for use to integrate a sub but it will work nicely for that and possibly tempt you to move the passive crossovers out of your speakers to allow an external connection in order to try an all digital three-way crossover.Requires more amps though but there is nothing like connecting your amps directly to the speaker drivers with no crossover components in the way. There is digital volume control for the individual outputs but the best resolution in any digital front end is had by running full digital level to the dacs and controlling the volume in the analog domaign right before the amps. This means multiple channels of volume control. As a result of this, I have recently discovered the improved sonics and low cost of stepped attenuators. Even in a two way passive cross setup they sound better than any active pre I've ever used. As far as the comparison between the analog outputs of the Behringer vs. the Tact I can't say, never having heard the Tact. I can tell you that the DCX sounds way better than my previous reference, the Assemblage DAC2.7 which is no slouch. The new 2496 AKM Dacs that Behringer is using are realy great sounding chips. Check the DCX users group for more info and even the schematics.
Regardless of what you connect it to, running digital out from a DEQ2496 will make fantastic improvements. You never thought your system had so much more to offer until you impliment a good digital eq.
The DEQ2496 has revolutionized my quiet listening since I ran an EQ tuned for quiet listening. Restores the perfect balance.
 
Many DVD players output a mutilated digital signal So keep this in mind when you first try the digital in on the Behringer SRC2496.
 
I have tried many different circuits to improve the sound of the 2496 Behringers. They all use the excellent AKM AK4393 dac chip which is unique in having a true balanced VOLTAGE output of 2v and enough power to drive through a passive stepped attenuator direct to the power amp. This direct out, capacitor coupled with film and foil caps, first order analog low pass filter, gives an incredible see through sound with the blackest of background. after trying many different output schemes I have settled on this one for it's sound quality and simplicity. All my evaluations were done on my DCX2496 which has a ribbon cable that allows access to the output of the dacs. The SRC is built with suface mount all on one board so tapping off this signal will be a bit trickier although I'm sure I can figure it out. Too bad Behringer refuses to send me a schematic. The analog out of the SRC must be different and actually sounds much better than the either the DEQ2496 or the DCX2496 so I wouldn't worry about modding it just yet. Most people will want a DEQ2496 following the digital out of the SRC anyway. During the course of my evaluations I have tried the following:
1. Bypassing the 47uf electrolytic interstage coupling cap with a .1uf Dayton film and foil cap. This simple mod made a nice improvement.
2. Behringer runs a crazy servo shifting balanced output stage. Because I'm running my amps single ended right now, I took the signal out before these stages for another small improvement.
3. I implimented a custom analog output board with LT1360 opamps and lots of bypassed filter caps. This was a huge improvement and nearly equaled the direct out scheme for sound but is obviously more expensive and complicated.
4. I tried multi-tapped Sowter transformers. These were easy to install, gave me volume control inside the unit and had an beautiful, liquid sound but were a bit euphonic and didn't match the fine resolution of the direct output. And they were obviously much more expensive.
I am going to compile my info for the 2496s on my web site so check back occasionaly to get the latest.
 
DEQ only dithers or samples to 96k with an analog input As far as spdif goes, pretty much any unit that accepts aes/ebu will lock to spdif in it's place. Just use a cheap xlr to rca adapter at the DEQ end of your coax digital cable. The AK4395 dac chips are available from Allamerican.
The digital out from my Philips dvd724 sounds like KEERRAAAP! The digital out of my Daughters Sony DVP NS500V sounds very, very, very good! As good as my EAD T1000. Maybe better. Those looking for a cheap transport can look no further than the cheap Sonys. The only complaint I have with getting one to use permanently is that the rewind/fast forward doesn't work when the player is paused. Other than that the remote handles just like a cd players. The toslink and coax outputs are so close (as they are with my M-Audio Firewire 410. Toslink has come a long way since I last gave it more than a passing chance.) that you might as well run it with the $15 Radioshack optical digital cable rather than the $60 Apogee Wyde-Eye.
 
The dac swap to AK4395 and "direct analog out" will apply to the SRC, DEQ and DCX2496 But if you like the SRC2496 you will also want the DEQ2496 for digital EQ running digital in. It is amazing. You never thought your system had so much more to offer. I will also fit stepped attenuators in place of the input and headphone volume controls and evaluate mods to the analog input of the SRC
 
I'm not sure why but dither on vs off makes a noticeable difference when running digital in, digital out, withthe SRC249 As does incresing the word length. (which shouldn't either?) Selecting dither on vs off in the DEQ2496 running digital in makes no difference as expected. I'm not sure what is going on with the SRC but turning on the dither creates a more spacious, fleshed out and musical sound, while dither off yields a more focused and direct type of sound. I usually prefer the dither on but it is close either way.
Yes, The SRC2496 makes my dvd's digital out sound much betterbut still not to the level of my EAD T1000 transport. Unfortunately, most dvd players don't output spdif without first having been through some clumsy processing. I'm going to start looking for a great sounding, cheap transport to recommend with the SRC but this may take a while.
The SRC2496 upsamples to 2496 with jitter reduction and dither Which the DEQ doesn't. Running an SRC in front of your DEQ2496 will make another gigantic improvement as upsampling really pays off. I haven't had the lid off of the SRC2496 to see what makes it tick yet but it sounds great on all counts and the analog out is even better than the DEQ. I also have mods coming for the 2496 line which take the analog to a higher level still. The dacs are changed to the AK4395 which is two steps up the ladder from the 4393 that comes with the unit. As the AKM dacs all output a line level voltage signal rather the current output that is found with the Burr Brown units, I'm running the dacs straight out to the stepped attenuators at my amps with no active circuitry! Talk about an imediate sound with a black background! The upgraded dacs also feature a soft filter option a la' the Wadias, which I haven't tried yet but should also improve the sound when running 96k data.

You have two new unknownsThe HT receiver and the digital out of the transport. I have just been doing comparisons of digital cables, aes/ebu Apogee wydeye vs coax wydeye with cheap adapters on both ends. The adapters are quite invisible so it is not that. Do you have any speakers that use a passive crossover? If so, you can compare the sound with your volume control (not the HT receiver, put that aside for now and keep the box handy) after the DCX with two channels set to full range which makes it into a dac, running digital in, to the sound using the volume control before the DCX while running analog in as you were before.

The level control is on the analog input of the SRC2496 so if you have analog sources that you want to run through the DEQ2496 you can send them into the analog in of the SRC (preceding the DEQ in the digital chain) which has a level control. The control allows you to set the level so as to saturate the adc section for the best resolution. Just set it by ear to get the best balance of sound with no audible overload. Run digital from the SRC2496 to the DEQ and put your volume control (preamp, attenuators, integrated, ect.) after the DEQ.

Differences Between 88.2 And 96 I did some more comparisons and now I would tend to agree that the DCX2496 is already upsampling within its own receiver chip. The differeces that the SRC makes to it are much smaller than to the DEQ2496 and definitely favor 96k over 88.2 as sending 96k into a unit already running at 96 is more like a pass through whereas going to 88.2 first requires an additional computaion. The SRC2496 does still improve the sound of the DCX making it slightly more open, but doesn't have as much effect as with the DEQ which actually undergoes the upsampling via the SRC. Using the SRC with the DEQ as the dac provides a better opportunity to investigate the differences between even integer and asynchronous schemes. The advantages of either are not cut and dried as some of the articles on the subject may lead you to believe. The differences are very small. Much less than changing cables or even the differences that I hear between brands of resistors in my stepped attenuators. So don't worry! Repeated upsampling in it's worst form, does very little to the sound. Apparently the computions are pretty accurate. As for the difference between even multiple and asynch through the DEQ, it comes down to choice, neither being obviously better than the other. 88.2 sounds a little more imediate while 96k seems a bit more spacious. Adding either one to a non upsampling dac will make a huge difference, cleaning up the highs and creating a more open and dynamic sound. Interestingly, when using my headphones through the excellent headphone amp in the SRC2496, I prefer a 96k sampling rate. 192 dacs would probably be even better. In my book, even vs asynch has no clear winner. Since all these upsampling schemes are available in the reciever chip that is in use, Dac manufactures should include the simple set of controls to let the listener make his choice.

 

Yes The SRC2496 Should Make A Big Improvement Yes an SRC2496 should make a big improvement in your case if your dvd player is anything like mine. The improvement to the sound of my dvd player's digital out was the biggest improvement to any piece of equipment that I tried the SRC2496 with. I would probably put the SRC right in the front of the chain so you can use the built in level control of the analog in.

 

Worse Than Integer multiple is relativeFirst of all I will have to double check my listening tests tonight but as I remembered it from the last time I tried it, 96k did indeed sound better than 88.2 with 44.1 input. The debate is still open as to the superiority of even multiple upsampling, as demonstrated by the decision of Benchmark to use an asynchronus method as they feel it is superior. In any case, any detriments caused by upsampling to either frequency seem to be far outweighed by the improvements or adding another da/ad conversion.

 

Unless there is a selection that I haven't found... Unless there is a selection that I haven't found, the digital output of the DEQ2496 reads that it is in the native digital in format, 44.1, as indicated by the input of the SRC2496 when following the DEQ. With Analog in, the DEQ can indeed be selcted to 2496. Either way the DEQ2496 is a must for digital in and digital out. If the DEQ does indeed have the Crystal 8420, (must be on the underside of the digital board?)it could be easily modified to offer selectable digital in upsampling but would the mod cost less than an SRC2496 and a radioshack cable?

I run all my analog single ended with cheap xlr to rca adapters and it sounds great. No need to let the balanced inputs and outputs prevent you from trying the behringer units.

The DEQ2496 is the opposite of muddy The DEQ2496 is the opposite of muddy. You would never believe your system had so much more clarity and focus until you really set up a good 31 band digital EQ by ear.

The headphone out of the SRC2496 sounds great through my Sennheiser HD545 imparting a warm and extended control of the bass that other headphone stages find dificult with the hard to drive HD545. I also tried running the headphone out as a variable feed to my amps. I wouldn't recommend this as a permanent solution, the sound becomes less detailed and thicker, but it could be used this way if your normal volume control went on the fritz. The only toslink that I have tried is the unusually great sounding optical out of my M-Audio Firewire 410. The M-Audio has the best sounding optical out I've ever heard (most others I've tried sounded inferior to their coax counterpart) sounding very close to the coax feed even with the SRC2496 set to pass through. I was dissapointed to find that the optical digital out of my iRiver portable sends the data only after a digital volume control meaning that the data is not anywhere near bit perfect and so is useless to me as a transport.

 

Behringer Strikes Again The SRC2496 Adac/Dac/Upsampler/Jitterbox is AWSOME! and the everyday price has been dropped to $130! The analog out is way better than the DEQ. Now I can see where some of the complaints about the analog out of the DEQ come from as just plugging one of these in without running through the EQ settings will sound weak in the highs. No such problems with the SRC. The jitter attenuation works wonders on my dvd player. The adc in has a level control that the DEQ for some reason omitted and while not absolutly transparent in stock form, adds a bit of power and liquidity to the sound. Kind of the opposite of the digititis one might expect The upsampler provides improved sonics after increasing the sample rate (this I can see) AND word length! (figure that one out). And it costs $130! I'm going to use two of these. One in for jitter and adc and one out after the DEQ. It's a good thing that I like the affordable Radioshack gold pcm cables for $12. They compare very favorably with the Apogee WydeEye. The SRC2496 has a great sounding headphone amp as well that could be used as a variable out in a pinch.

The SRC2496 Will Regenerate The Data At whatever Rate You Select Altough I only have a few hours of listening in, my initial impression is that the effects of the SRC2496's upsampling are all good. I'm not sure about the rates and word lenghts in the DEQ but it seems that it will output the same format as the input, up to 2496, even though the dither is selectable to 24 bits. I will make a more thorough post on the SRC2496 after I get to know it better. My next test will be to compare the digital in when using my reference transport vs the toslink from my IRiver portable vs my cheap dvd player.

The Behringer DEQ2496 Sounds Better Than My Assemblage Dac2.7 The Behringer DEQ2496 sounds better than my modified Assemblage DAC2.7 which was very close to the Musical Fidelity Upsampling Dac when I compared them in a shop 2 years ago. The Assemblage Kills my Enlightened Audio Designs DSP1000mk3 (I sold it after it sat around in it's box for two years). I have also borrowed the Monarchy Dac2A which had less resolution and a euphonic, boring sound compared to the DAC2.7 . The Assemblage, Modified with LT1360 opamps and wide open analog filter values, has a lot of resolution and throws a deep sounstage but the DEQ2496 sounds wider, taller and even more resolved and fleshed out while still being easily musical. And I haven't even opened the lid on it yet! Not to mention it's an easy to use 31 band EQ with 1 button recall of stored settings for different gear/speakers.

 

Analog in is always tough with any digital processor Analog in is always tough for any digital proccesor. To get the best sound you need to put the volume control after the DEQ or, for volume control before the Behringer, have the gain structure of your system perfectly matched so as to have the analog input meters at the proper peak when the volume level in the room is at your reference listening level. This is not a problem with pro amps as they all have a volume control on the amp. Either way, volume before or volume after, to get any decent sound quality with analog in the input meters must be peaked while listening. Otherwise, you are using very few of the available bits in the analog to digital converters. This situation turns a 24/96 machine into something like an 8/96. As far as the 48 vs 96 goes you must have found a selection that I don't know about. I have seen selection for dither. I prefer the dither turned on at 24 bits, but I don't recall seeing any choice for sampling rate.

Check Out The Noise Spectra Of The AKM Dacs With output filterless Dacs all the rage, these AKM chips are a prime contender. They also feature a voltage output rather than a current output so I run my DCX with the Dacs capacitor coupled directly to the output connector eliminating any active circuitry between the dac chips and the amps. As easy as it would be to mod I haven't even been tempted to open the case of the DEQ as it sounds great in stock form.

I Have An Audiophile Dac With Burr Brown PCM 1704 Dac chips And the Behringer sounds much better. The Assemblage Dacs were known as "parts graves" with unbelievable parts counts and very high quality but the new AKM dacs are really in a new league. I also use a DCX2496 and interstingly enough, The analog out section is different from the DEQ and doesn't sound quite as good and of course, using the analog in, preceeded with a volume control on any digital processor will yield the poorest sound as you are only using a small portion of the available bits. The real beauty of the DEQ is had when used with the digital in. I haven't had a chance to try the Dac1 but if you find that a more expensive Dac such as the Benchmark sounds better you will still want the digital eq of the Behringer running digital in, digital out, for room correction. For $250 the DEQ2496 is a steal.

Got Digital Out? Need a new digital source? Digital technology is moving so quickly that upgrading your source will probably make a big improvement in your sound. I was looking for a digital equalizer, so I tried the Behringer DEQ2496. I had planned to use this with digital in from my transport and digital out to my modified Assemblage DAC 2.7 but as it turns out the analog out of the Behringer sounds even better so I ended up getting an equalizer and a new dac for 300$. If you haven't ever tried a digital eq then you are missing out . No matter what the rest of your system is you will deffinitely benifit from some room correction and eq. Add to this the fact that you are getting a great sounding dac and you have the current no brainer in my recommendations for your next upgrade.

 

The Deq2496 has replaced my Assemblage Dac2.7 The Behringer is a step up from the Assemblage (which I did have a chance to compare, quite favorably, to the popular Musical Fidelity upsampling Dac from a few years ago) offering a wider and taller sound stage with even more transparancy. It did benefit from a long break in (off and on for thirty days) sounding slightly opaque at first. I haven't tried the benchmark but you can always use the eq through the digital out if you find a better Dac. Digital volume controls are best left to full resolution so I use stepped attenuators for the volume control as they sound much better than any PreAmp that I've had.

Even 5 year old gear costing thousands will strugle to play in the same ball park as some of the newest Dacs. New upsampling reciever chips, dac chips, dsp chips, opamps, caps.... All better.

 

you can get +-15db digital volume control but... My experience with the digital volume control in my DCX2496 is not surprisingly very bad as digital volume controls throw away bits. I much prefer using passive stepped attenuators on each input of my amps.

 

The switching power supply is dead silent. I can't measure any noise or ripple with my 2 meg scope. Why would you automatically discount the AKM dac chips? As a dac, this unit sounds really nice (after a longer than normal break in), as digital eq this is a must have.

 

I use mine with a cheap rca to xlr adapter on the digital in. There is a menu choice to tell the unit to expect spdif or abs/ebu data. The same type of adapter will work fine for the digital (or analog) output as well.

 

Trans vs.Active Output Redux It seems the biggest improvement I heard when switching from an active to a transformer output stage came about simply from the transformer attenuator eliminating my 20k passive resistive attenuators and the short six inch cables that followed them. I've since done some more development on the resistive stepped attenuators building a "shotgun" type which plugs right into the amp with no output cable. The series resistance was also re-evaluated. I tried 1K, 2K and 4K. 1K was noticeably loading down the source, thickening the sound. 2K drove a one foot output cable a little better than the 4K but the 4k attenuators were close through the cables and, when plugged into the amps shotgun style, were more effortless and open than the 2k or the trannies. (And alot cheaper.) The transformers still hold the slight edge in grace and ease but the optimized attenuators allow the active stage to sound deeper and more detailed. Next I'm going to try mounting the resistive attenuators inside the case of the DCX, following my active stage and preceding a buffer. I'll let you know how this sounds.

Opamp Class A Bias Mod I tried the class A bias mod in my pre which is a stepped attenuator into an opamp for a gain of +9 db, followed by a class A mosfet output stage configured within the feedback loop. I used a Jfet configured to 2.2 ma.( a little excessive I know but this is still dissipating less than half of the rated power of the opamp and since this is followed by another stage I would expect that the drawbacks I experienced would be further magnified in the more common situation where the opamp is the final output device. ) from the output of the opamp to V-. I listened back and forth several times but found the sound to be better without the mod. It seems that if you already use a great opamp such as Linear Tech LT1360, this mod may be a step backwards. The midrange improved slightly, taking on an additional ease, but the bass became slower,slightly mushy and seemed to lag. The highs lost some microdynamics and sparkle lending to a more boring sound. Audition for yourself but don't assume this mod will be an automatic improvement.

 

Op Amp Upgrade I like the Linear Technologies opamps. LT1360 for single, LT1361 for dual. No need for the even higher speed LT1364. These amps from LT are incredible with a see-through detail second to none! They also seem to be very tolerant of less than ideal circuit parameters such as DC on the input or offsets between + and - in the power supply. Analog Devices AD811/AD812 are a bit warmer but can't match the detail and are fussy to implement. Burr Brown OPA627 are nice as well but again can't match the LT for see through soundstage. When swapping single opamps watch out for different configurations of the output offset compensation circuit. Some companies use V+, some V- . ( only single opamps have this ) If unsure when swapping singles just leave Pins 1 and 8 bent out as all these high-line amps come trimmed for low offset output.

 

Linear Technology 1360 For singles I prefer the LT1360. I have compared these to OPA627 and OPA134 in my Velleman K8021 pre amp and find that the Linear Technology amps, although a little more susceptible to switching noises, offer a more transparent presentation. The Burr/Brown OPA627 is a bit warmer but can't quite match the see through detail of the LT1360. The OPA134 has a slightly thicker sound with far less expansive image depth. This is not to say that the OPA134 is a bad amp as they easily outperform off the shelf types but only goes to show how great LT1360 and OPA627 really are. Anyone still using the term "slop amps" have never tried these top of line amps. Linear Technolgy offers the LT1360 in a dual amp under the number LT1364. I have compared these to Burr/Brown OPA2134 in the input of my Velleman K4005 power amp and, though the differences in this application are smaller, prefer the see through quality of the LT1364. When you consider the price of the Linear Technology op amps, $4.00 and $6.00 at Digi-key, they are a steal.

Velleman K8021 Pre And K4005 Power Amp - High end sound for 450$I'm using these and the sound is excellent. The amp sounded great right out of the box easily replacing my Arcam Delta 290 integrated. It sounds even better by substituting a LT 1364 for the op-amp. It would undoubtedly sound even beter running two of these in bridged mono. This amp turned out to sound so good that I hav'nt tried any of the more expensive amps. The K8021 pre needed some mods but sounds great now. I changed the line amps to LT 1360 and removed all the litle yellow shunt caps and even the input coupling caps and the sound is now pure and detailed. I tried opa 627 and opa 134 but the LT amps really are the best I've found and are only 4$. The input switching works great as does the ability to select between gain settings on the fly. Headphones sound awesome as does the MM phono stage. Order them from Q-kits in Canada and let the exchange rate work for you.

 

Re: Best hookup wire? I prefer Cardas 21 or 19.5 which is available at Handmade. Fine stranded and indvidually enameled. No individual strands touch each other. Sounds very detailed and open yet composed unlike other stranded wire where the strands can interact where they touch each other which can lead to a scary, confused quality. Be sure to tin the Cardas well to get the enamel off all the strands at the connections. Another wire I like is Nordost Flatline 12 ga. This is wonderful speaker wire which easily replaced my modified Kimber 8 TC and is available at Madisound.com . This wire is a flat ribbon of individauly teflon insulated, small rectangular section solid core conductors. Cut them appart for a hook up wire that is easier to strip and has a smooth musical sound but not quite as extended in the highs. You can audition different wire before building with it by making interconnects out of it first. I use a three wire braid. two grounds with a 100R resistor at one end of one ground, this end at the source. I replaced all my Straightwire and Audioquest interconnects with home built.

Biasing opamp into class A... I tried the class A bias mod in my pre which is a stepped attenuator into an opamp for a gain of +9 db, followed by a class A mosfet output stage configured within the feedback loop. I used a Jfet configured to 2.2 ma.( a little excessive I know but this is still dissipating less than half of the rated power of the opamp and since this is followed by another stage I would expect that the drawbacks I experienced would be further magnified in the more common situation where the opamp is the final output device. ) from the output of the opamp to V-. I listened back and forth several times but found the sound to be better without the mod. It seems that if you already use a great opamp such as Linear Tech LT1360, this mod may be a step backwards. The midrange improved slightly, taking on an additional ease, but the bass became slower,slightly mushy and seemed to lag. The highs lost some microdynamics and sparkle lending to a more boring sound. Audition for yourself but don't assume this mod will be an automatic improvement.

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