Here is my Bottlehead Foreplay preamp. There is no better bang for the buck audo gear than
Bottlehead. Mine is constructed with Doc's fine grain magnet wire and is faily stock at this point. Major mods that I've made to date
are the additon of the reverse recovery spike filter, upgrading the PSU caps to Panasonic FC's and the coupling caps to Auricaps.
Also, I lined the inside of the wood base with copper foil to reduce RFI.
I've rolled a number of tubes through my Forelplay. To date, my favorites are the RCA cleartops and the RCA blackplate 12AU7's
and blackplate 5963's.
One of the things that makes Bottlehead projects so rewarding is the existence of the
Bottlehead Forum at AudioAsulum where like-minded tubeheads congregate to discuss construction methods and tweaks. You're not alone while
building this kit.
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| Foil-lined Foreplay Chassis |
Dynaco ST-70 An all-time classic tube amplifier made during the late 60's. This one was "rescued" from EBay. I
rebuilt only the parts that were out of spec and replaced the input and output jacks with sturdier components. The input jacks
are spaced further apart so that larger RCA plugs can be used.
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| Click to Enlarge Image |
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| Click to Enlarge |
The input jacks are mounted on a piece of Formica that was a sample chip from Home Depot. The dimensions and spacing
of the mounting holes are shown in the accompanying drawing. In mounting the jacks in the chassis, care must be taken that
the outer barrel of the RCA jacks does not touch the chassis. Click on the Drawing to Enlarge Note that the dashed
oblong area in the drawing depicts the opening in the ST-70 chassis and shows how the jacks will fit in the opening.
Consonance Ella Is a push-pull amp similar to the ST70. It produces about 35 watts per channel using EL34 output
tubes and 50 watts using KT-88's. It is avialable in kit form from my friend Kevin Haskins at
DIYCable.com. Construction is relatively straightforward as all major parts are already mounted on PCB's. Construction entails wiring
up the power supply and the inputs and outputs. Kevin offres high-quality magnet wire for chassis wiring which is a worthwhile
option.
Another worthwhile tweak for this amplifier is to replace the coupling caps with better quality ones. Shown here is the
main PCB after installation of Auricaps.
I really like the sound of this amp, especially with KT88's it puts out some decent bass. With EL34's it is about equal in
sound quality to a good working ST-70, but with KT88's it surpasses it. I recommend this amp to those folks looking to get
an introduction to tube audio who don't have the skills to rebuild a Dynaco. Building one of these will give you a very nice
introduction to tubes.
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| Mian PCB of Ella with Auricaps Installed. Click to Enlarge |
COLE Phono Stage Click on the picture to read about the Cole Phono Stage.
