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Old 16th July 2007, 11:05 PM   #1
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Default TCJ Cathode-Coupled Amplifier

Hello all...
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.

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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)

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Old 17th July 2007, 06:19 PM   #2
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Old 17th July 2007, 06:28 PM   #3
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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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Old 18th July 2007, 06:05 PM   #4
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Thank you...

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