trinityamps.com

Hi.
I'm so impressed with my new plexi 18 I'm thinking about rewiring my old Traynor YBA1 to have Stephens front end but keep the EL34s output.
But I'd have to rethink the PI cause it has the 2nd input for the NFB. What is it about the various 18 s around that no NFB is required? Would an El34 output amp without NFB be plausible? I guess I could leave out the "normal" Channel. Do you think the two 470K mixer resistors colour the tone in a typical fender/marshall 2 channel arrangement?
Thanks all.
Going to bed now.
Stew

You can build an almost identical amp to the Trinity Plexi, using an EL34 power stage. In the PI you will need a 15k tail resistor instead of the usual 18W's 56k or 47k. And the Trinity Plexi's 470 ohm PI cathode resistor, instead of the usual 18W 820 ohms, is also good to have in an EL34 amp.

The NFB just makes the amp feel tighter, especially in the low end, as well as delaying the onset of breakup. You can have NFB in Marshall 18W amps, and some folks have been known to add it in. It's really just a matter of personal taste.

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Great tones come in small glass jars!

Ahh Yes!! BUT can you have an EL34 amp WITHOUT NFB? Inotherwords an EL34 amp with the same layout as an 18.
Stew

Sure, quite a few 18W style amps have been built with an EL34 power section. There's also the Matchless Chieftain, Matchless Clubman and the Marshall 2046, none of which have NFB.

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Great tones come in small glass jars!

....??

So would these non-nfb 18/el34 amps have sloppy bass ,early breakup ect? or has another method been introduced to replace the NFB effect?
I ask because I'd like to use the second i/p to the LTP PI the same way Trinity's 18's do.
Stew

It's all relative. Apparently, your Plexi 18 also suffers with early breakup and sloppy bass.

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Great tones come in small glass jars!

Touche'.
No my 18 doesn't. But my YBA1 does IF I disconnect the NFB.
Maybe if I went U/L I could eliminate the NFB.
Stew

Yes, but the Traynor is a totally different amp with a circuit designed and voiced with NFB as part of the equation. The 18W architecture has other ways of keeping low end under control. And you don't hear a lot of complaints about flubby bass with Matchless' EL34 amps. And for UL, you would need to invest in a new OT.

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Great tones come in small glass jars!

I have a Hammond 1650K in her now. with the u/l taps tied off so I'm good there. So then I'll just play around with the PI like you suggest and see how it sounds!
Stew