@bonzo75 . Big fella. What is SET meant for. Why do we have high 100+ watts tube amps these days.
SETs are best used where with the right speakers you will have more nuance, agility, purer tone, flow, compared to a non-SET, without giving up energy and bass. This is best done when the speakers require very less drive, less grip, less power. Optimal speakers for this are extremely few in number - full rangers without crossover or simple two ways with minimal crossovers and woofers that can be easily driven. The moment you require more drive, power, grunt, grip, and you use low powered SETs, you will get restrictions in dynamic range, and bloated, slow sound. At this point push pull valves and later high quality SS amps start sounding better. So the people who report bloat and distortion on SETs simply haven't heard them with the right speaker.
Ok, above is general theory, what does it mean in practice? If you have a speaker, and the chance to rotate amps, you will find certain speakers sound better as you move from high powered to low powered amps. Certain speakers sound better as you go the opposite, e.g. in the same room, with the Airtight 300b 10w amp and the 34 watt Airtight EL 34, the 300b sounded better on the Devore Orangutans, while the EL34 sounded better on the Cessaro Wagner (the Wagner was sounding restricted with the 300b, the Devore had more nuance, flow, ease with the 300b without giving up anything on dynamic range or bass). And yes, if anyone wants to know, I preferred the Devore even with the EL34 to the Wagner, but that is beside the context of this post.
In another room, the Devore sounded better with NAF 2a3, compared to Silvercore 833c (20w) or a 300b 20 watt amp or a jadis 100w integrated. But the NAF 2a3 had very restricted dynamic range with the Lansche in the same room and that required more power, ideally the Jadis. Now the Silvercore seems less nuanced compared to NAF 2a3 on the Orangutans, but comparing on vintage Tannoys, it is much more nuanced than KR audio integrated, and we preferred the SIlvercore even though there the KR had better drive and bass - the silvercore had enough to have a better balance with the added nuance.
Just to clarify, when I say nuance, I hear it in more inflections, and more notes within the same period, be it violin, or piano, or cello, or vocals. More intranote detail, rather than being glossed over.
Apart from Airtight, we have also done same manufacturer compares with Thomas Mayer's 46 vs 211 on Pnoe, and also compared NAT Magma on it. Compared Silvercore 883 20w to another 833c Audio Music 120w amp on a harder to drive speaker.
The small tubes are mainly 45, 46, 2a3, 4p1L, 604, AD1, PX4, PX25. There are many, too many to hear, but if you try two and your speaker runs out of steam you will know. There are extremely few speakers in this category of tubes. You will have to build your own with vintage woofers in a simple 2 to 3 way, or get a commercial full ranger like Pnoe or build one with AER or Lowther based on your budget. Or you will have to biamp the woofer with a more powerful amp. Unfortunately, the experience of this forum with such tubes and well matched speakers is pretty poor compared to others.
Now, as you start crossing 10 watts requirement, you will find that these NAF 2a3 types, which are not single ended but PSETs or push pulls like Cubes EL84, start sounding very good. They are bringing in more drive and still having sufficient nuance. It will then be a toss up between them, and a 211, or GM70 types. You will immediately lose nuance but gain drive and power compared to single ended 45 or 46, so overall on such speakers the higher power will sound better. Does the transformer matter? Of course. But I don't know anyone who puts a 211 transformer on a 45 amp. That is also why the lower power SETs are quite low cost - they just require much less in material.
There could be Lamm at 30 watts, Kronzilla at 50, special ones like Allnic which do powerful versions with 300bs which go up to 50 watts. If you need more than this you are really into territory with one or two SETs like NAT and the rest push pulls like CAT, Audio Research, VAC, etc. There are some exceptions, mostly one offs, like the KR VA 200, or Eimac based SETs like the Trafomatic Elysium which cross 100 watts. If your speaker has impedance dropping and requiring more drive and grip you are then requiring quality solid state amps (which I prefer to push pulls like AR or VTL or to these powerful SETs like NAT at that stage, i.e. on speakers like Apogee, Martin Logans, or any of the regular cones like Wilson, Magico).
