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6SN7 Preamp

Hello
Due to circumstances, I am selling my 6SN7 Preamplifier.
i-bd6dJZ8-XL.jpg


It was my main preamp for a time but as my wife and I aged,convenience became a factor and remote control became a necessity.
For this project, I chose the Glassware PS1 solid state power supply. It regulates both the high voltage plate supply and the low voltage filament supply for the preamp tubes ensuring clean and pure DC power is supplied to the audio stage. As it is solid state, no maintenance or adjustments are ever required.
i-sKvJsqh-XL.jpg

The audio circuit is the Glassware CCDA circuit. The CCDA offers some real benefits over traditional tube circuits where it uses one half of the tube as a constant current source to improve linearity. The other benefit is that only two tubes are required for operation. As the 6SN7 octal tubes become more and more scarce this feature means you only need two matched tubes.
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The signal travels from the 4 position input selector switch to two 5 position dual mono attenuators, one for each channel. These cut signal level in 0.5 dB steps to allow for gain mismatches elsewhere in the signal chain allowing perfect centering of the stereo image. This is very useful, maybe critical when trying to get the most out of feedback free single ended amplification.
i-gpwxTrz-XL.jpg


The volume potentiometer receiving those signals is the legendary Alps Black Beauty, which operates with a smooth and silent silkiness that will perform well for years to come.
i-XgnVKWZ-XL.jpg

After amplification by the CCDA circuit, the signal is sent through a switch allowing you to have two output caps and select which you want in circuit. In my build, I have a Teflon cap and a russian oil filled cap that I can choose to route the signal through either or both depending on my preference at the time. The caps are easy to swap out so you can customize your sound to your liking.
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I chose to enclose the tubes and circuits to allow for a more domestically acceptable and safer build.
Switch layout is L to R, Output cap selection, Volume, Left stepped attenuator, Right stepped attenuator, 4 position input selector
The pre will ship with the excellent Sylvania 6SN7GTB as shown but I’ll include a number of other pairs that you can roll.
The preamp has a gain of 10 (20 db) which is just about right for today’s signal sources.
The Zout is a low 400 ohms making this a good match for many solid-state amps.
Sound quality is as one would expect from Glassware design, which is to say excellent. The design really allows the 6SN7 to perform at its best.
I am asking $700 shipped CONUS for this beauty.
I will include 4 extra pairs of 6SN7 to roll for your enjoyment
Thanks for looking today.
 
+1



I'm just looking at that and really liking what I see. : )
I've got some red bank 6SN7s and two 5-slide in things
of some of the nice vintage Sylvania triangle plate 6SN7s
and some strange sort of Military 6Sn7s also.


So how would this do as a pre for something like a CitationII in triode mode?
or front end for a Marantz 8b?


Good stuff. Good stuff. Please don't lower the price.
Just don't do it please.


I feel weak.


My empty wallet is complaining!


Cheers,