This turned up for sale on a Facebook group.....I ended up trading another amp for it, probably got the bum end of the deal, but the heart wants what the heart wants, you know how it is. 1973 Musicmaster Bass. Really interesting little circuit. 12AX7 preamp valve. Two 6AQ5 power tubes, which are basically the same as 6V6 but in a physically smaller package. That's it. It's like Fender said "how can we make the simplesst amp in the world?". CTS speaker. Take a look at the chassis.....there's almost nothing there. On my messy workbench (ignore the other amp above it). Same chassis as an AA764 Champ. What's really interesting, for other amp geeks, is the transformer at the bottom right-ish. It's an interstage transformer, and the the primary receives a signal from the preamp valve, and then a signal is fed from one end of the secondary to a power tube, and the other end of the secondary feeds an out of phase version of the signal to the other power tube. Voila! No need for a phase inverter valve! I'm guessing that maybe it was cheaper for Fender to buy a bunch of these transformers than pay for another valve and the labour to add a few resistors to make a normal phase inverter. So, how does it sound.......?