The beauty pictured above is the Chazz Headphone Amplifier which is produced by DIYHiFiSupply out of Hong Kong and distributed in America by my friend Kevin Haskins at DIY Cable. It's a single-ended Class A headphone amp with a heavy duty choke-filtered power supply that uses 6550 or KT88's for output tubes. It can produce 9 Watts in ultralinear mode and 5 Watts in triode mode and the sound is simply awesome. It's one of the few headphone amplifiers that can power the AKG K-1000 headphones (actually earspeakers). For those of us with more normally-priced headphones, Chazz can capably drive headphones of any impeadance. I've used it with Sennheiser HD-600's (300 Ohms), with AKG K-301's (120 Ohms) and Sennheiser HD-280 pro's (64 Ohms) and it drives them all well.

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Construction is straightforward and starts with a bare chassis containing the transformers and a PCB containing most of the parts for the power supply. All of the wiring is point to point and is made easier by the use of small terminal strips to which most of the passive components are attached. The terminal strips are attached to standoffs at each tube socket and make access to the tube socket pins easy. This method of construction also encourages tweaking since unsoldering of parts from the tube sockets will genreally not be necessary. Here's what the chassis looked like after attaching the tube sockets and wiring up the filament supply and the power supply.

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After wiring up the power supply and filament supply the inidividual tube circuits are constructed. Here's the rectifier tube and the 6SN7 input tube circuits. Notice the heavy wire in the center of the picture to which all the black wires are connected. This is the star grounding point to which all of the ground connections are made. The sue of a star grounding scheme helps to assure low noise.

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Next, the output tube sockets are wired up. Shown here is one of the output tube sockets with the feedback network and input capacitor attached.

All that's left now is to wire the input and output connections. Chazz comes with an Alps potentiometer but a DACT stepped attenuator is also available. Adding the DACT will be my first tweak of Chazz. Chazz features both a standard 1/4-inch phone jack and a 4-pin Canon jack which is included to accomodate the AKG K-1000 headphones.

Once it's all wired up, the last thing to do is bundle the wiring to keeep noise low. Notice in the picture below how the wiring is routed across the middle of the chassis and then downward through one of four "vias" between the tube sockets. This keeps everything away from the signal wiring and promotes low noise. My unit had less then 0.3mV of noise and is dead quiet!

And how does it sound? Glorious! The combination of a tube power supply coupled with the KT-88 output tubes gives this unit a very ballsy sound with good detail and ambience recovery. Running in ultralinear mode produces a very nice wide soundstage while triode mode produces a sound that is more "intimate". I don't prefer one mode over the other, both are nice and I find myself switching between them just for some variation.

Tweaking I upgraded the supplied Solen coupling capacitors to Auricaps and liked what they did for the sound. I've also rolled some tubes into Chazz as well. My unit came with Valve Art 6550's and the first tube I tried in their place was the trusty Valve Art KT88. The KT88 had more slam than the 6550 and I've always liked the Valve Art KT88's, which I run in my Ella amplifier.
Switching out the Valve Arts for a pair of S.E.D. (nee Svetlana) KT88's was a step in the wrong direction. I still can't say what was missing, but I noted that I quickly grew tired of listening to Chazz when the S.E.D's were in. Then, I got really lucky and scored a pair of Electro Harmonix KT88's on EBay. With my cans, these are THE tube for Chazz. They have tone and PRAT! I can listen to Chazz for hours with these baby's in there.