SET Lovers, what's the one solid state amp you love(d)?

I'm thinking of trying out a solid state amp in place of my 300B SET, which is giving me some problems again and the builder is swamped so it's going to be awhile.

Suggestions? Speakers are 96dB 12" 2-way bass reflex studio monitors from a Japanese recording studio.


Would you say that in your experience with Class D speaker matching is easier or more difficult?

Compared to a tube amp, easier! Most speakers are designed to be 'voltage driven' which is to say that the amplifier is supposed to be a 'voltage source'. A voltage source will put out the same voltage regardless of the load. To do that a very low output impedance is required. This is stupid easy with class D and difficult at best with tubes, so in theory a class D amp should be a lot easier to match with a speaker. There are limits, such as extremely low impedances which will reduce the Q of the output section filter in a class D amp, but its pretty well-known that tube amps don't like really low impedances either so that's pretty well moot.

The only exception might be ESLs. Some ESLs, like Sound Labs, have a pretty significant impedance peak in the bass, and expect the amplifier to be able to make the same power into that peak as it might in the mids and highs where the impedance is much lower. In general a voltage source doubles power as the load impedance is cut in half which also means that the output power is cut in half as the load impedance is doubled. IOW a voltage source might have its 8 Ohms power cut in half or in quarter with such speakers (Sound Labs have a 30 Ohm peak in the bass region). So tube amps can work out well on such speakers where a powerful solid state amp won't be able to make power.

In addition, the capacitive load of ESLs can mess with class D amps that are not of the 'self oscillating' variety. This is because the capacitance of the load is in parallel with the inductance of the output filter of the amp, setting up an electrical resonance which can result in ultrasonic oscillation. I know of at least one respected class D amp that suffers this trait and can fail in this application (with possible damage to the speaker as well if not properly protected). Our class D is self-oscillating and so does not have this problem.

@soix makes some interesting bass amps. Powerful and quite lightweight with some heavy hitters playing with them. You can see where this is going...

@atmasphere:  do you expect to see Class D amps that can drive a continously low impedance (e.g., 1 ohm) in the bass at high power?

@atmasphere Ralph, I was recommending your GaN amp elsewhere on this site, but his speakers do drop below 4 Ohms I think in the upper bass range, but there are no specs I can find for your amp if it’s stable down to 2 Ohms and what the power output would be (same for AGD amps BTW).  Could you maybe elaborate on that a bit here?