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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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In Reply to: I want to build a parallel 845 SET amp posted by MIchael Samra on October 11, 2006 at 22:40:38:
I have no experience with EP transformers, but I'll make a suggestion for the circuitry.Current hogging between parallel tubes is frequently a problem. At low frequencies, it can be handled with separate bias arrangements. For cathode bias, that means separate heater supplies for the two tubes, and separate cathode resistors and bypass capacitors. (If you use AC, hum balance becomes somewhat complex!!)
In that case, one always worries about keeping the AC signal current properly split when the tubes, cathode resistors, or bypass caps are not well enough matched. The "ultrapath" connection, with the last power supply capacitor connected to the cathode instead of ground, gets the cathode bypass out of the loop, which I expect would help a lot. The trick is, with parallel tubes you can use two ultrapath caps, one to each cathode. Being film caps, they can be better matched than the usual electrolytic bypass caps. Thorsten has posted often with ways to choose the cap values optimally.
Hopefully Gordon will post about the problems at higher frequencies, which often cause subtle problems with parallel triode amps. AFAIK, he has the best knowledge and most experience in that area.
Sounds like a very interesting project. Keep us posted!
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Follow Ups
- Re: I want to build a parallel 845 SET amp - Paul Joppa 23:11:10 10/11/06 (0)
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