We were asked to make a valve pre-amp for a customer who wanted a simple clean Fender-style pre-amp, mainly for playing jazz.
Here are some of the parts before the build.
The PCB is a charge pump circuit from Tube Town that boosts the incoming voltage (12VDC in this case) to a user-adjustable 90-220 VDC. The idea was to power the pedal from an easy to source 12VDC supply; you can wire a 12AX7/ECC83 heater to run on 12V, and the HT can be supplied by the charge pump so that the valves are running at a decent voltage. By the way can you spot the mistake?
Here is the final assembled unit:
The circuit is the Blackface Fender AB763 circuit. I added a master volume to control the overall level of the output, and final output is buffered with a high-voltage MOSFET source follower for low impedance output.
The circuit was hand-wired using PTFE eyelet board. Sorry that there are no snaps of the inside but the customer wanted to use it at a session so I didn’t have much time with the final unit.
