50VA is more than enough. For a 4 Ohm load thats exactly the right spec of transformer.
The Output valves are cheap as chips and a quad can be ordered direct from one of the eastern European countries for less than the price of a single new EL84. This is a totally unused valve so will remain cheap for the foreseeable future. The QQE03-10/12 is the western version and will be slightly more expensive than the Russian version which is the RY-17
Shoog
The Output valves are cheap as chips and a quad can be ordered direct from one of the eastern European countries for less than the price of a single new EL84. This is a totally unused valve so will remain cheap for the foreseeable future. The QQE03-10/12 is the western version and will be slightly more expensive than the Russian version which is the RY-17
Shoog
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I already have some push-pull OPTs. Would a 5k anode-anode OPT work for this? I have a pair salvaged from an old junked receiver. I also have a pair of PP EL84 OPT's I could press into service (specs unknown, I only know that they were meant for PP EL84's). I don't know how to translate specs from a 50VA toroid to the usual EI core audio output transformer.
I have some EL83 too, which I got for very cheap.
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I have some EL83 too, which I got for very cheap.
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FWIW, The schematic I posted earlier in this thread shows this, except global, instead of short loop, NFB is employed. 6BM8=ECL82! The Edcor O/P trafo shown is inexpensive and the setup has good performance at the frequency extremes. Look closely and you will see brute force phase compensation being employed. A builder lacking an o'scope is not in over the head.
"Full wave" doubling the O/P of a Triad N-68X isolation trafo, with hefty sized caps. in the doubler stack, is a cost effective way to obtain a high performance B+ PSU. Such a PSU would work well with triode wired 6V6 family tubes or triode wired Russian 6p15p to yield approx. 2 WPC. Add a 5965 or 12AV7 for voltage amplification and the OP would be in "Hog Heaven". No loop feedback, whatsoever, needed mated to high sensitivity horn speakers. The "problem" with this sort of setup is the cost of O/P "iron". When "budget" O/P "iron" is inside a GNFB loop, behavior at the audio band frequency extremes is frequently acceptable. Without that help, better quality magnetics are needed. Decide where you will compromise. TANSTAAFL!
That's great news. Then I don't need to spend money on OPT's! 🙂
OK, can I use two EL86 instead of the one RY-17? I already have a bunch of Russian equivalents that I bought for really really cheap. If those are a go, then I believe I've finally found a design I can build completely from parts on hand. That would be nice.
I also have a few 500VCT 150mA rated power transformers I bought decades ago, and a couple of power supply chokes I can use to make choke-input filters. That should give me about 220V B+ supply good for 100mA or so.
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Dual mono's not a problem. The 500VCT transformers are pretty small, since they only have the 500VCT winding and a 6.3V winding, no 5V winding. I got them from Fair Radio, for like $6 USD each, something like twenty years ago.
So does that mean a pair of EL86's with joined cathodes and screens is a pretty close approximation of an RY-17?
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So does that mean a pair of EL86's with joined cathodes and screens is a pretty close approximation of an RY-17?
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EL86 would be closer than a EL84 or EL83. Should work with joined cathodes and joined screens.
My main amp is fully differential and direct coupled and uses EL86's at about these voltages - it sounds really good, similar to the old Leak Stereo 20 I once had - but much cleaner and better bass.
Shoog
My main amp is fully differential and direct coupled and uses EL86's at about these voltages - it sounds really good, similar to the old Leak Stereo 20 I once had - but much cleaner and better bass.
Shoog
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I tried both the 6E5P and the 6P15P and the latter was better to my ears, but both are great tubes well suited to a low power SE amplifier:
http://www.diyaudio.com/forums/tubes-valves/280167-yukon-gold-spud-amp.html
Please follow Forum Rule #18 - don't quote each other if you are the next poster, the redundant quotes have been removed.
Hey Shoog --
Just letting you know, based on simulations, it looks like that RH Slayer push-pull/single-ended circuit looks very good, but gives limited output power (same as an SE EL86, or whatever). I stumbled on an SE 'E-Linear' 6550A circuit that looks too good in simulation to ignore. I posted about it in another thread.
http://www.diyaudio.com/forums/tube...ea-se-ul-amp-local-feedback-output-stage.html
I have the power transformers and tubes available, along with just about all the other parts. All I'd need are a pair of OPT's, which I'd get from Edcor. It seems no matter which circuit I decide to try, I'll have to buy something.
Anyway, thanks for your never-ending stream of good ideas. (Now I really need to build something!)
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Just letting you know, based on simulations, it looks like that RH Slayer push-pull/single-ended circuit looks very good, but gives limited output power (same as an SE EL86, or whatever). I stumbled on an SE 'E-Linear' 6550A circuit that looks too good in simulation to ignore. I posted about it in another thread.
http://www.diyaudio.com/forums/tube...ea-se-ul-amp-local-feedback-output-stage.html
I have the power transformers and tubes available, along with just about all the other parts. All I'd need are a pair of OPT's, which I'd get from Edcor. It seems no matter which circuit I decide to try, I'll have to buy something.
Anyway, thanks for your never-ending stream of good ideas. (Now I really need to build something!)
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