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In Reply to: RE: Resistor dissipation Question posted by timp on September 16, 2012 at 12:53:37
Question,
Are your Finals (output tubes) fed from C2, and your front end tubes fed from C3 and C4 ?
If so, you need to PSUD input the Finals current draw if ( 180 mA??) right after C2, and PSUD input your Front end draws after C3 ( 15 mA??) and C4 ( 5 mA.??).
Follow Ups:
Jeff. You are right! C2 is the for the power tubes.
You might consider using a 5R4 to drop more voltage in the rectifier. Also lowering the input capacitor value bfore the 6H choke will make a difference. Try 4.7 to 10 uF with a motor run cap. One other idea is to use a CL-150 inrush limiter on each leg of the transformer, as this will also drop a few volts.
Jeff,
Nice post. I agree with much of what you said. However, the large voltage drop in a lovely sounding ( directly heated !!) 5R4 comes with a price to pay, higher Z.
A single 5R4 is best used in a preamp. Too whimpy for a stereo P-P amp seeking to play back dynamic expressions.
Jeff
The addition of 250 Ohms resistance after the rectifier tube, and the use of a 122 Ohm DCR choke, prior to the Finals, are causing a loss in dynamic capability of your audio amplifier.
There is NO combination of chokes ( that I can see ) which will get you close to the 377 VDC you seem to want to use, when you start with a 386 VAC 20 Ohm power transformer, IF you seek to retain a tube rectifier.
Off the top of my head, to optimize the amp would take a lower VAC secondary on the Power Transformer. Ugh, got milk ??
Jeff Medwin
Right now the 4 6bg6g are drawing 150ma.
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