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In Reply to: RE: inductances and loadlines..... posted by mqracing on May 21, 2009 at 12:50:00
Michael- Thanks for taking the time to explain this, and I realize there are trade offs and no one spec makes or breaks a transformer. The intricacies of all of this is obviously over my head. Let me just ask you to advise me on this.
I think you've seen the circuit I'm trying to build, It's something I want to try, but if it doesn't work out, I'll try a more conventional design. Whatever I end up with will be a PP class A amp, running either 2A3-40s or 300BXL tubes. The dual center taps are required.
If you were building a beast like this which would be your choice, in the $400.00 (possibly a little more) a transformer range. I could go slightly more, but would have a tough time affording the price of the Peerless 20-20 plus.
twystd
What aspect of the circuit demands a split primary?
I was thinking of a parafeed PP with CCSs on the plates. The center taps have caps that return to the cathodes.
twystd
You know there is no particular reason to put caps to the cathode in a shunt feed PP. If you had a center taped primary you could put a cap between the two sections to insure no unbalanced DC in the windings. But it would probably sound even better to balance the current some other way and eliminate the caps all together. Then you do not need a center tap at all.
Google Marcel and Clovis by Phil Sieg. He has built an amp along these lines.
Michael
Yes Marcel and Clovis is a really interesting design. The design I'm thinking of uses the garter circuit to balance the tubes. I can't have a shared cathode resistor for the garter circuit to work, so it's a PP stage rather than a differential stage.
PP amps usually require a cathode bypass cap for full power. By putting the cap returning to the cathodes, I don't think I'd need a cathode bypass cap, plus they block any DC on the transformer. The thought is to have a really balanced PP stage, with minimal capacitors, and taking advantage of no DC, unbalanced or not, on the transformer.
No telling what it will sound like, it's just an experiment I want to explore. I haven't seen a schematic like it before, and neither have my local DIY friends, so thought it might be interesting. If it shows promise, I will release the schematic to the DIY community. If it sucks oh well, I'll just drop back and punt to something more proven.
twystd
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