The Amp Garage

Man that is a friggin awesome sound. Love it!

Apart from the KT66 the other big difference to the JMP or JCM is I always understood the JTM45 to have an 8K OT. But I'm now reading that depends on the era like the different output valves used.

That's really impressive and sounds great in the clips. Thanks for posting them.

What's the whole combo weigh out of interest?

Decent rule of thumb for tube rectified supplies. The one-step-finer rule is 1.4 * AC minus the rectifier drop and any resistive losses in the transformer. Sorry R.G. but no, I use that rule of thumb for diode rectifiers. Valve recto is even lower. The factor you have missed is the first cap ripple...

We say diode rectified gives 1.4x AC voltage as the DC, but this is unloaded. My rule of thumb for valve amps incorporating the first filter cap ripple has always been 1.32x. 330 x 1.32 = 436VDC so in my books you're spot on where it should be.

I originally put in a Vox style Cut Control on my Marshall 18 Watt style build. Very different amp to yours but I also found it to be pretty useless. Not much later it was ripped out and the front panel hole used for a VVR pot.

For me usually electrical tape (because I've got it on hand and it's soft) folded over on itself.

Thanks. Floating the heater supply at half the 170V B+ was inside the submini valve cathode to heater voltage spec and meant I could get B+ and heaters from a single 0-30V transformer.

Keep us posted with your build!

I had a client that wanted a jazz amp as a single channel version of the Gibson GA-75 with some specific extras (switchable preamp stage local NFB, effects loop, bright and treble bleed). It turned out very nice for finger style jazz playing.

I bought a number of 6J32P a while back when everyone was buying $2 Russki valves. They've been great in my 18 Watt with EF86 channel, reliable and not microphonic.

Guts and size comparison.

And some pics. 16 years ago, I still have the amp and it sounds great.

Here are the final schematics including PI/PA VVR.

Through some breadboarding, I found a 220k plate resistor gave me the most gain out of a 6112 preamp stage. Anything bigger and gain dropped off again despite what the plate curves said in theory. Then I tested bias point between grid clipping and cutoff and got the following values of cathode resis...

I also socketed them. Soldered the submini into a DIP-8 machined pin socket. I made a PCB for my amp, so it also has DIP-8 machined pin sockets for the valve locations. Then the submini socket plugs into the PCB mounted socket matching orientation marker. My submini build was 16 years ago. I'll dig ...