SET amps ?

I don't think any particular topology is inherently superior. A lot depends on implementation and system compatibility. I own two good pushpull amps (a pushpull 45 amp and a 349 amp) and a 2a3 SET (actually a parallel SET). I like both the 349 and the 2a3 SET a lot, perhaps the pushpull 349 more than the other, but, then again, the linestage I currently use is specifically matched to the 349 amp.

In a heartbeat, I would trade either or both of these "favorite" amps for a particular OTL amp that I have had the pleasure to hear. Unfortunately, these particularly amps take up WAY too much space and are extremely expensive, which is why I passed on a recent change to own them.

The SET amp is particularly good at presenting all of the fine detail, nuance, and complex interplay of instruments without being harsh or brittle sounding (a problem with many supposedly "detailed" gear). The 349 pushpull amp is not quite as open on top and does not quite have the same delicate touch as the SET amp, but it delivers a more propulsive bass line and has a fantastically realistic midrange. The OTL I heard is so immediate, punchy and alive that it is startling, yet it is smooth and not the least bit harsh sounding.

Conversely, I've heard plenty of, to me, crappy sounding SETs, pushpull amps (not heard a really crappy OTL, though many have turned out to be somewhat high maintenance).

Charles1dad,

The OTL amp I mentioned is an amp built in the late 1970's by someone in Greece. It was never a "commercial" product. I have been told that the builder made about 10-12 amps, two of which were brought to the USA by the Greek ambassador in the 1990s. I cannot recall what kind of tubes are utilized, but, I understand that the tubes are old television sweep tubes. I also understand this amp utilizes the Futterman OTL design. The amp puts out about 30 watts.

Each of the monoblocs is massive--each contains a huge toroidal power transformer and four smaller toroidal transformers. I understand that in each monobloc there is essentially four separate power amps, including four separate power supplies, hence the four transformers. The previous owner had it for the past ten years and pretty much kept the amp on and in standby all the time; the output tubes were never changed in that time and very little adjustment to bias has been required (attesting to how gently the tubes have been run in the amp). I know the owner of the other pair of these OTL amps that is in this country. That other amp is actually a different version and has 4 boxes instead of two.

What is particularly striking about these OTLs is how they make even small and lower-cost speakers sound surprisingly "BIG" and ballsy and alive. OTLs, in general, are good at doing this (you could call it a parlour trick); this OTL is particularly good at this game.

I have no problem with any kind of music selection as far as SET amps are concerned. If they are paired with suitable speakers, they can deliver clarity, detail, weight, and do everything quite well. But, they are considerably harder to match with speakers, given their low output and quite high output impedance than a pushpull amp, and probably harder than an OTL given how low the output of most SETs (an issue for me because I prefer the 45 and 2a3 tube over 300b or 211 or 845). But, I also agree that most of the lower priced models do not deliver the goods--it really does take high quality output transformers to get decent SET sound and that does not come cheap. I've heard a few of the supposed giant killers and the sound of these tend to be quite bad--anemic, dead and too light weight-- in the setups I heard (perhaps the amps would have sounded better with easier loads).

OTLs are no different from other amps--each implementation/tube type sounds different. Atmasphere and Joule OTLs, for example, sound very different and which is "better" is a matter of taste.

I have been quite impressed with the Horning systems set up by High Water at several shows. They were driven by top of the line Tron amps and Thoress amplification. This is a very dynamic, and immediate sounding system but Horning manages to tame the midrange peakiness I would have otherwise expected from the Lowther-based midrange driver. But, I would guess that that kind of midrange speed and detail makes this a VERY picky system when it comes to amplification.

I agree with Charles1dad that ease of driving is particularly important. I think it is much more important to matching with tube gear than efficiency. I heard low-powered amps on a pair of original 15 ohm Rogers 3/5A speakers sound wonderful in a quite large listening room. Those are something like 83 db/w efficient, but at 15 ohms nominal impedance, very easy to drive. A lot of fairly efficient speakers, like Wilson speakers, seem to be particularly challenging to lower powered tube gear because they have a load characteristic that is not suited to such amps.