More Tubes = Better Sound

I prefer more power AND less tubes. One input tube, one output tube, 200WPC SET.

Midlife Crisis Mono

IIRC, Atmashpere's comment has to do with better impedance "matching" between his OTL amps and speakers.

what are the advantages to having a lot of tubes, assuming that you have very efficient and sensitive speakers (the OP has some very efficient Klipsch speakers)?

There is less advantage in this situation. What such speakers do allow is that you can have a situation where clipping the amp becomes impossible (we have lots of horn customers...). That in itself is valuable but not germane to the thread.

IIRC, Atmashpere's comment has to do with better impedance "matching" between his OTL amps and speakers.

This is incorrect; what I said was if one is to have multiple output tubes it is better to have a lot than a few. IOW in a larger transformer-coupled amp this holds true just as it does in our OTLs. This, as I mentioned previously, holds true as long as there is a means to allow for current sharing between the output devices.

Could one take away from this that with the Ref 75 and klipsch speakers, clipping the amp is very unlikely?

"In theory," fewer tubes mean less concern with mismatched tubes, which means less muddled sound. A lot of purist won't even except two output tubes per channel in a parallel single-ended setup for this reason.

But, in practice, there are quite a few advantages to more tubes to achieve a given output. One advantage is not having to run the tubes as hard. When run well under their rated output, most tubes will last MUCH longer, and this may actually mean lower cost for tube replacement than another amp that uses few tubes but pushes them much harder. Using multiple tubes in parallel lowers the output impedance meaning a lower turn ratio for the output transformer (arguably a positive result), or in the case of OTL amps, a lower output impedance seen by the attached speaker (higher damping factor).

One of my all-time favorite amps is a custom-built OTL amp that uses many tubes to achieve a 35 watt output. The tubes in that amp, which is often left on for months at a time, have not been changed in more than ten years and still test new.