Paul Speltz Zero-Box Autoformer With Tenor OTL

I’ve not heard an auto-former on any speaker so I don’t know how it sounds.  But, I too am skeptical about putting a transformer on an OTL.  Ideally, OTLs would be used with higher impedance speakers, so I can see why someone without the right speakers might cheat a little with an auto-former even if that is less than ideal. 

I had the first pair of Tenor OTL 70’s in the US, purchased directly from the NY audio show. They were with the volume controls, but as amazing sounding they were, suffered from reliability problems, and were fussy about speaker loads. Finally a lightning strike did them in. A few years back, I purchased a newly manufactured pair from the new Tenor Audio, with all the modifications and updates which are reliable, never an issue. They are still in my collection of tube amps, and I love them!! They sound beautiful with the built in volume controls, but I prefer driving them from my Audio Research 40th Anniversary preamp. It’s a sound that hooked me 25 years ago, and I missed it when I didn’t have it. Of course, with any OTL, speaker impedance is important. I don’t think it would be a good idea to try to change the impedance with an Autoformer, but I have no experience with that. I just think it would alter what makes these sound so great. Amazing on a Quad ESL 57, or a stacked pair wired in series. 

I’ve read numerous reviews on these as I was considering them at some point to for my setup and the reviews were very positive. There is also a substantial window to return if they don’t help. In my case, I spoke with Paul and he recommended trying other options first.  He was very friendly and responsive via email and then phone.

glen

I tried Speltz Autoformers with Atma-Sphere M-60 OTLs powering 91 db flat 6 ohm speakers. Thought they significantly degraded the sound and returned them.

You should have enough power for Rockports.