Quad ESLs with Tenor OTL amps

Has anyone used Tenor OTL amps with any Quad ESL speakers? I have had the pleasure of owning previous OTL designs by both Futterman/NYAL and Counterpoint in systems with Quad 63s and USA Monitors, and consider it to be one of the great synergies in audio. I currently own Tenor 75 Wi amps and would like to try them with Quad 988s or 2805s, but am interested in whether anyone else has tried this combination.

The good folks at Tenor are reluctant to endorse the match, as the protection circuitry in the Quads could potentially short the output of the amps, which are not protected from such an occurrence, and would likely, as a result, sustain damage. I am told that, in this sense, the Tenors are quite different from other modern OTL designs, such as the Atmaspheres, which are protected. I do own Zero Autoformers, which might help mitigate the potential problem.

I am most anxious to have any information or hear any accounts of attempts, successful or not, to use these products together, as well as informed opinion as to why it should or should not be attempted. Many thanks.
The Tenor will work fine with the ESL63s insofar as power is concerned. The ESL 57s will be over-powered and the potential for damage is high if a tube fails. For the the newer Quad designs, you will have enough power but will find the ZEROs handy as the newer designs have low impedances since Quad is trying make the speaker more compatible with transistors. Despite that they still sound better with tubes.

ESLs in general can be damaged by arc-over events in 6C33 power tubes. It is this arc-over issue (as well as a limited service life of the tube sockets) that kept us from extensive use of the 6C33 in our own designs, and why you are getting some reluctance from Tenor. I would consider placing an in-line fuse in the speaker circuit to prevent damage if a tube arcs. I would set the value at 2.5 Amps and see how that works- you might have to go up to 3 amps but I would not go above that. That way the fuse will blow if the output power of the amp is exceeded, which can happen during an arc-over event.
I would follow Tenor's reluctance and act in accordance with it by not making that particular match if possible. Ralph at Atma-Sphere is one sharp cookie who knows his stuff about tubes and OTL's. He's right and then some.
Also, the Autotransformers will not serve or function as a fused or protected output would in case of a blown or arcing tube. Even if they have isolation properties to them as transformers often do (if designed that way for that purpose), they are for impedance matching, not protection, or at least primarily so. Perhaps a different speaker system would be a good idea. I wish you success and safe and enjoyable listening. Tom