• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

TCJ Cathode-Coupled Amplifier

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seventenths

Member
Joined 2007
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.

tcj%20cathode-coupled%20amplifier.png


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)
Thanks

7/10
 
SY

SY

Ex-Moderator
Joined 2002
SYclotron.com
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.
 
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