A friend of mine brought over an interesting device he has developed, a high power booster for low power SET amplifiers.
The device is a simple no feedback unity gain power mosfet current amplifier with a 100 ohm input impedance, a very low output impedance and a 60 watt per channel power rating. It even has regulated power supplies. Its kind of a power amplifier with no gain stage and no small signal transistors at all, just a pair of mosfet output transistors.
You simply plug in the audio outputs from your low power SET amp into the device, and then plug your speakers into the output of the device. Now you have a 60 watt output with no load interaction. Your SET is not working at all driving the new current booster so its linearity is improved and you are no longer limited to super efficient speakers and load interaction. Dan suggests that tube life should be improved too as they are not putting out any power at all, just their normal voltage gain.
In my reference system the sound was very impressive. His SET amp could not of worked with my 83 dB efficient speakers at all, but now it could, and really really well.
Could there be a market for this device? It would cost less than $1000. It would not be an AVA product as it is not needed with our amplifiers (unless you wanted a high power Ultravalve), but Dan is willing to build them for others himself.
Frank Van Alstine