For this final project, I am planning on designing and constructing a lunchbox tube amplifier. I am planning on using two 12AX7 preamp tubes and a single EL84 power tube in class A operation to put out approximately 6 watts of power. There will be high and low channels that can be used independently or in parallel for more preamp distortion, as well as a Baxandall tone stack and a master volume. Other creature comforts will include an effects loop, switchable impedance, paralleled speaker outputs, and a standard removable power cable.
In designing the control scheme, I used an 8″ x 6″ x 2″ chassis size (Hammond 1444-862) for reference, which seemed reasonable enough at the time. However, immediately after constructing the model of the chassis, it became apparent that I would need way more room. More height is necessary as the controls barely fit, and that leaves little room for labels. More surface area will also be necessary as I need more room to fit both of the transformers I’ll need as well as to comfortably fit the PCB. I want to aim for a sort of “open” design on the inside for ease of servicing, so more room is always better.
Other than that, I’m relatively content with the control layout and block diagram, so I just need to get working on the schematic and grab a larger chassis. Out of the available chassis produced by Hammond, 1444-10825 would likely be a much more usable size at 10″ x 8″ x 2.5″.