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|16th July 2007, 11:05 PM||#1|
Join Date: Apr 2007
Location: Kingston WA>
TCJ Cathode-Coupled Amplifier
I recently finished up my first tube project (a Bottlehead S.E.X kit)which turned out better than expected and I would like to move forward with a simplified scratch-built project. I thought I'd give John Broskie's "TCJ Cathode-Coupled Amp" a try.
My initial plan is to use Edcor's XPWR104
with a pair of Tung Sol 5687s. Ok so far?
I feel confident that I can safely follow the schematic, but I have a question regarding the heater circuit. JB suggest referencing the heater circuit to +40 V. How do I do this? Does this mean that my heater circuit should be 40V-46.3V (low-hi)
|17th July 2007, 06:28 PM||#3|
Join Date: Oct 2002
Blog Entries: 2
You've got the basic idea. Make a voltage divider between B+ and ground out of two resistors sized so as to draw a milliamp or two and for their junction to have about 40V on it. Bypass the lower one with an appropriate cap to ground (1-100uF).
If you're using DC heaters, attach the (-) end to the junction point at 40V.
You can do something a little trickier which will really suppress common-mode noise and that is to build your heater supply with two regulators, one +3 and one -3. The common point is then the one biased up.
The heaters should be locally bypassed for RF.
“A philosopher is a blind man in a dark room looking for a black cat that isn't there. A theologian is the man who finds it.” - Mencken
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