This is a cool unit. I bought it a few years back and used it a handful of times. It has a few uses.
It can be used as a preamp into another amp to get a nice tube tone. The cool thing about it is that the signal passes through the power tube, not just the preamp tube. All the tube preamps that I know of only have a preamp tube. This unit takes the tone from the power tube too. There are two outputs...1 is an 8 ohm output for use as a stand alone head (see below). The other is an output for driving another amp. When this output is used, the 8 ohm output automatically has a dummy load, so it can be used without a speaker being connected to it. (I don't know all the technical info involved, but you can use just the line out safely without a speaker connected.) It also has a level control on the back for the line out. You can connect it to a power amp, but I prefer to use another head that has more control over eq, etc. It has a volume, tone and gain knob, and a low shape selector.
With the gain knob, you can use it to get an all-tube overdrive tone. Just connect it like above and work the gain higher than the volume. It is power-tube saturation, but you don't have to get to ear splitting levels to get it....unless you want to.
It isn't going to be a heavy distortion...it is more of a light tube overdrive.
Finally, it can be used as a stand-alone head, though I would say that it is not even loud enough for a practice amp. Just plug in an 8 ohm cabinet.
The tube set is (1) 6V6 and (1) 6SN7. This was hand made in the US.
Now, it isn't going to make a class D amp sound like an SVT, but it is a cool unit that can bring new dimensions to the tone of SS amps.
Price is $350 shipped.
Here are some pics: