sneaky update...

Got home from work today and thought I'd try the 45 through the single 12" in my combo, just to make sure the tiny buzzing noise I heard on notes wasn't to do with the speakers in the 4x12.

Either the magic wiring faeries fixed it while I was at work, or it's something to do with the 4x12 cab. Through the 8 Ohm 12" it sounds perfect all the way up to 'too loud'.

An impedance related wiring issue? (the cab is 16 Ohm and the Single is 8 so I'm switching on the back of the amp), a voice coil rubbing? (the speakers -are- 50 years old), or just a vibration somewhere?

I'm sure if I could stop playing it for a second I could figure it out, but I've really been having fun getting familiar with it!

The tone controls work nicely, although the bass comes on thick and fast. I suspect the louder I go the more I'll end up cutting the bass back, but we shall see. The high treble channels are super bright with the stock 100pf cap (I have a silver mica here) and I've been digging the normal channels a lot more. I might try a couple of different caps in the bright channel there and see what I like. I've heard Marshall went anywhere from 100pf to 500pf on this circuit over the years.

I hope to get the MV wired in on the weekend, and I'm very keen to see it sounds with the inputs jumped and both volumes cranked, but with the MV reigning it all in.