Okay. But I'd rather see you finish your OTL first...
-This text is also on the RM-9 MK-I vs MK-II thread as the OTL question was also asked there.
OTL amps for 8 and 4 ohm speakers, or speakers that have dips below that, require a large number of tubes and fairly complex circuitry. The SA-4 amplifier I designed for Counterpoint has eight output tubes per channel. With that many tubes mono-blocks are the only way to go and it's not an inexpensive adventure initially or later in tube replacement. It is pretty at night though.
I have recently completed an OTL design for direct driving electrostatic panels at the 5,000 volt range. The circuit is similar to an SEPP or SRPP (those terms seem to be used interchangeably). The resulting amplifier has some very nice qualities, the main one being enormous peak power capability of 2,500 watts with only four output tubes.
Scaling this down in voltage and adding an output transformer of special design I propose to make an amplifier that is class A up to 20 watts, AB up to 40 watts and have a peak output of about 100 watts.
This is what most people really need for listening to music. I rarely measure more than a few watts in most systems played loud. Granted there are some very power-hungry speakers, in large rooms with high SPL listeners and I already make the RM-200 for those. However, most of us are better off with an amp that gives us a good class A power range and lots of peak power for headroom. There is no need to be class A on the peaks.
Amplifier rating since the FTC passed it's testing rules in the mid 70's has skewed amplifier design in a high RMS power direction. I think they got several things wrong, especially the 2/3 power pre-conditioning test that made large heat sinks and heavy power transformers necessary. The pre-conditioning test should be done at a much lower level of 10-20% because that's what music is.
Tentatively I plan to make this a line level integrated with 3 inputs, volume and a power switch. I hope to price it around $1500. It is going to have big tubes with plate caps, because that's where the high peak power is to be found.
