SET for 88 dB 4 ohm loadspeaker

Monomithos,

Power requirements are so dependent on one's listening level and size of room, it is hard to say whether any SET amp will be sufficient for your needs. I would say don't overlook pushpull amps; many sound fantastic and some don't even give away any of the "magic" of SET (just ask those who listen to ruinously expensive, but incredible sounding Western Electric amps).

Personally, I don't like most higher power pushpull amps based on pentodes, like the 6550, KT-88, etc. Some pentode amps based on EL-84s actually sound good to me, though they don't have that little something extra of low-powered SET amps.

My absolute favorite is low-powered SET amps (based on 45 or 2a3). But, my speakers are reasonably efficient (99 db/w, have a high impedance, and I don't play them very loud). I do think you give up something with higher powered SETs, but some are very nice sounding. A friend had a Wyetech that used 211 tubes that sounded very good.

Now, for something completely different. While I really do like the way SETs reveal fine textures and detail in an unforced manner, there is a quite different magic that is available from OTL amps. OTLs are incredibly dynamic and lively sounding. The compatibility issue there is that they work best with higher impedance speakers. Still, I've heard them on a wide range of speakers and really liked the sound too.

Audiofeil,

One of us is confused here. What do you mean by SE push pull? Aren't the two designs, single-ended and pushpull inherently different? Single-ended means that one tube (or set of tubes in parallel) reproduces both halves of the wave form (by modulating DC current flowing in the primary). Pushpull means that tubes reproducing the opposite halves of the wave are connected to the opposite ends of the primary, with the DC voltage at the center tap.

I don't know anything about the amp you mentioned, but it could be a triode, class A, pushpull amp. But I don't see how it could also be single-ended.

Tvad,

Thanks for the link. The amp shown is a parallel SET. It has two output tubes per channel, but it is NOT pushpull. Rather, the two tubes are hooked up in parallel. Not only does this increase output, it lowers the output impedance of the amp.

I know there are a lot of SET purist who say that configuration does not work well. I have no idea if the drawback of this configuration outweighs the advantages. What I can say is that my amp (Audionote Kageki) is a parallel SET (2a3 tubes) and it sounds great to me.