Layout adjustment 1

Doghouse for some of the filter caps

Recently, when I was dry-fitting the large components to get a sense of the space in the chassis, I realized my plan for laying out the three 22uF filter caps along the front edge of the circuit board would not work because the backsides of all the potentiometers (tone and volume dials, which in my design are duplex pots, twice the depth of the normal ones on the standard Bassman) would trap the relatively large caps in place, preventing easy maintenance. And filter caps are one of those things that sometimes need replacing. The advantage of putting them there would have been that they would be physically close to the portions of the circuit they serve, while not taking up space on the circuit board, which I wanted to keep as small as possible. This was an idea Doug Hoffman showed in some process photos of a 60's era Fender he was renovating.     

So, the current plan is to relocate just those three caps to the outside of the chassis, in their own compartment (doghouse) to prevent the high voltage leads from being accidentally shorted. The location will be very near to where they would have been, just on the other side of the chassis panel, maintaining the physical nearness to the circuit, yet getting them out of the way and in a location better for maintenance. 

I made and mounted a little circuit board just for them (circled in red).

No selectable speaker impedance 

When I was thinking of what I wanted in my design I thought it would be good to have flexibility in what speakers I could use with the amp. Other amps I've had offered multiple speaker jacks supporting speakers of various impedance, and I've found that useful. Many outputs transformers (OTs) have multiple secondary outputs taps to drive different speakers, often including 4, 8 and 16 ohm taps. I assumed mine offered such options as well, what with all those wires, so that's what I designed for. Actually the array of wires on my O45RS OT are on the primary side to better match various power tubes, and on the secondary side it has just one 16 ohm tap. Turns out, this is really just fine - it's slightly less efficient, but driving a single 8 ohm speaker works just fine with that tap, or I can drive two such speakers in series, both of which are options for me. The efficiency issue probably only produces subtle audible difference at high volumes.  Removal of the impedance selection switch actually creates a bit more distance between wires in that area of the chassis, which could help limit any interwire signal interference. It also requires a change in resistor values to drive the switchable negative feedback circuit, since that circuit will now be fed from a 16 ohm output tap instead an 8 ohm tap. 

That part of the layout plan now looks like this: