Sorry for the gap between posts. There has been a little too much real life lately and I haven’t had as much time to work on this as I’d have liked.
I have refined my schematic a little bit and I think it’s more or less in its final state.
I’ve removed the effects loop (turns out they are a little more complex than I’d hoped) and the tone cut (got some advice that it really shouldn’t be necessary with my circuit).
I’ve also made a few additions:
- A ‘brownface’ tone stack switch, which adds an extra capacitor and resistor to simulate the 6G4-A Super-Amp circuit.
- A built in -9dB L-pad on the output
- A built in resistive dummy load
I’ve also changed to tube rectification from solid state. I already have the tube wired into the chassis and I have some voltage to shed so I thought I’d give it a try. It’s also relatively easy to change to solid state at a later stage if I need to. This is intended to be a test bed amp after all.
I was given the idea of using a power scaling circuit to further reduce the B+ voltage to a manageable level. I intend to use this to drop the voltage to 420V so that I can use the power circuit from a Deluxe, which also used 6V6s. I am using a fixed bias circuit for this amp so, unfortunately, I will not get the full benefits of the power scaling. Instead I’ll have to mount the pot inside the chassis so that it can’t be fiddled with. I will be able to move it between high and low power but any change would mean re-tuning the bias voltage so that’s not exactly a quick exercise.
I’m hoping to order the parts this week and with a bit of luck I’ll be able to make a start over the weekend. I’ll start with the chassis work, which will include removing the last few items that I don’t need, installing plates over the existing holes and of course drilling the holes for the new components. I’ve got a rough idea of how I’m going to lay it out, but I think that I’ll wait until I have parts in hand before I actually start cutting.
The plan after that is to wire everything point to point, partly because it’s supposed to give better tone/less noise but mostly so that I can play with the layout more easily going forward.
I’ll try to put together a rough sketch of my layout a little later in the week.
