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In Reply to: RE: Resistor dissipation Question posted by timp on September 16, 2012 at 12:53:37
Did you mean to draw this with a half wave rectifier? If you use a full wave bridge (solid state) and terminate C2 with a 160mA load, the supply will output about 385 volts of nicely filtered B+ for the power tubes. It will unfortunately also exhibit an impedance "bump" at about 15 Hz, but this may or may not be problematic. The bump can be smoothed if you interchange the first two filter caps so that C1 = 23u and C2 = 47u.
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Buy Chinese. Bury freedom.
Follow Ups:
I bet he was "meaning" a full wave center tapped rectifier circuit.
No matter what, I would swap C1 and C2, I agree with you.
I don't think there is any getting around a new power trannie to do the amp properly.
Jeff Medwin
You guys are amazing! Ok. I come clean! Jeff you are absolutely right. I have a full rect of b+ 386 per side with a center tap. I was lazy that I did not measure the tranny value. From one b+ to the other b+ measures
83 ohm. Did I measure it right?
TRY to "input" into PSUD2 what is really going on, to the best of your knowledge.
Insert a current tap before R2 and assign 150 mA. as its value.
Change the current tap at the end of the filter to 50 mA. OR better yet, add current taps after R2 and R3 to accurately reflect actual current draws, at different locations along the filter.
If 83 Ohms is the DCR across the entire winding, use half of that ( 42 Ohms) as a ROUGH input figure in PSUD, which will be ( not exact but ) an improvement over the 20 Ohms and 83 Ohms you have inputed.
Hi Jeff
Thanks for helping me. I am extremely thankful. And I learned a lot in the process. I am still confused... I just read voltage on the plate and it says 377.
Somehow, Duncan's PSU says that the reading on C2 is 350ish. So, I may be doing something wrong?
To add more info,
I am using 2 12sn7gt as phase inverter
and 1 12sl7gt as a premp section.
Then 4 6bg6gs as power tubes.
In short, looking at my PSU, do you see any problem using it for a pp amp?
Thanks.
Tim,
That PSUD2 simulation above looks mighty fine to me, and WOW, you have come a long way on this in a very short time.
I would NOT worry about the difference in VDCs of 27 VDC on a 350 VDC supply, that is less than 10%. Is 377 VDC what you wanted ?
What you did is totally opposite of how I would approach the filter to the finals. See my NEW post above, " Pinging ...timp."
Cheers,
Jeff
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