TCJ Cathode-Coupled Amplifier

seventenths · 16th July 2007, 10:05 PM

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.

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

seventenths · 17th July 2007, 05:19 PM

bump...

SY · 17th July 2007, 05:28 PM

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.

seventenths · 18th July 2007, 05:05 PM

Sy,

Thank you...

7/10

16th July 2007, 10:05 PM	#1
seventenths diyAudio Member Join Date: Apr 2007	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. 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

17th July 2007, 05:28 PM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	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. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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17th July 2007, 05:19 PM	#2
seventenths diyAudio Member Join Date: Apr 2007	bump...

18th July 2007, 05:05 PM	#4
seventenths diyAudio Member Join Date: Apr 2007	Sy, Thank you... 7/10

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