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.
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. |
@mrdecibel The ZEROs can really help solid state amps sound better driving lower impedances- they aren't just for OTLs! |
Ralph, can you point me in the direction of someone using a beefy solid state power amplifier that are using the Speltz zeros, so I may hear from them their opinion. Mcintosh continues to use autoformers in many of their designs, but a Krell, Boulder or even a Parasound are able to handle the impedance dips in most speakers. It is my opinion, and this will not change, that the Speltz units are band aids for tube amplifiers, such as you OTLs. A properly designed amp should be able to handle this task. I see no need for a speaker with very low impedance dips, nor of low efficiency. Can we just leave it at that. My best, always, MrD. |
