Push-pull Tube Amps and autoformers


I’ve gone and done it and decided to marry my 1.7i Maggies to mono Quicksilver M60s that only output 60w per. Crazy, I know. But the sound is sweet, and mellow for my jazz, though yes, at lower volumes, and they certainly do not allow the Maggies a full sprint, like with the Parasound A21+ that I can switch to (Luxman AS-55) when I want to throw-down serious dBs. But still, I would like a bit more punch from the QS. So, that led me to Paul Speltzer’s Zero Boxes. I talked with Paul (great guy to talk things through with), and he wasn’t certain that the “push-pull” QS would benefit from the Zeros, (because they were originally designed more for OTL amps like Atmospheres.) But, after talking it through awhile, we thought it worth the 60 day return trial period to see if the Zeros might help add that punch, if I use the 8 or 16 ohm taps. They arrive in a couple of weeks, so I’ll know soon enough. But, in the meantime, any of you have input, or experience with using autoformers (or auto transformers) with push-pull amps like QS? (Please give me a pass on bad speaker/amp impedance matching, ok? I knowingly signed-up for low-powered tubes for my 84db Maggies because others I trust on this forum have had good things to say about doing crazy sh-t like that. And, its just a trial. So, chime in gently, please.

128x128audiodidact

@mrdecibel and @audiotroy, thank you both for the heads-up. I’m aware that the Zeros were initially meant for OTLs (I noted such above, in my opening post), but I did speak with Paul Speltz and while he is not promising anything, he felt it would be worth trying to see if the Zeros might help the QS with the Maggies. I actually have a pretty beefy SS amp (Parasound A21+), still in the system, that I switch between it and the QS with a Luxman switcher. The QS produces a lovely detailed sound at lower listening levels, especially at night (I’m talking 65-70db). The SS is for everything above 80db when I want slam. The Zeros may very well not pan-out, but they’re on their way and I’m going to try them at various taps and settings and see what happens. And i’ll be quick to post the results, whatever they are, good or bad, when I’ve finished.  Yes, I hope to get just a teeny bit more from the tubes, and yes,  it just may not be in the cards, but the proof of the pudding is in the actual eating, so, I’m going to take a bite and see for myself, though I had initially hoped to find  someone here who’s actually tried something like this. But, thanks again, everyone!

Oh, I should mention that I modified the  1.7i Maggies recently with GR Research external crossovers.

I’m a very happy customer. The autoformers allow me to use the 8 Ohm tap on my ARC 75SE. SQ is excellent, at higher volumes the amp is working effortlessly. I’m also using an analog crossover at 60hz for my subs.

Yours is a perfect application for autoformers. And not an uncommon one.

I recommend you let your ears be the judge.

I used the Zeros for about 4 or 5 years with a PP Elekit TU 8340  and various tubes(EL 34, KT 77 and KT 120) driving ML Electromotion ELS, Quad 63s and ET LFT 8s. The Zeros were most effective with the Quads and the Martin Logans.

YMMV

with your particular tube amplifiers you do not need the Speltz Zeros, as I am surprised Ralph is saying it is ok. They were created for OTL amplifiers.

@mrdecibel The ZEROs can really help solid state amps sound better driving lower impedances- they aren't just for OTLs!