Switching Guitar Amplifier heads the right way

With the Jansen Bassman 50 done I needed a way to use my Marshall cab with both the Bassman and the JCM800. I was too lazy to keep unplugging stuff all the time so I started building the Aiken Amps head switcher.

I had downloaded the schematics from Aiken Amps a long time ago as the site was often going down, now it's gone forever by the looks! The general idea of the project was to have the unit switch the guitar signal as well as the main load of the heads between the cab and a 200W dummy load. Heres the schematic if you need it.

Finding the Parts

The Aiken schematic uses a make before break concept using 5 volt relays. Surplustronics had a bunch of these laying around so I grab enough to make 4 or 5 of these units incase friends wanted one and I couldn’t get parts anymore. I had ordered some 100W wirewound resistors a while back as well.

I also had some leftover alloy chassis from Monaghan Sheetmetals nicely corner welded. A bit of drilling and test fitting the wirewound resistors I got on eBay and it all seemed like it was going to come together.

Test fitting

There was some old computer CPU heatsink paste laying around to use for the resistors and the I could wire them up. I did the rest of the wiring on stripboard with solid core wire. I will most likely make a PCB for this and swap it out or make a V2 and sell this one, one day.

Figuring out how to wire it up

I had a bit of trouble figuring out how to lay it all out since there was only a schematic. The notes said to physically isolated the two circuits, but I just kept the separate on the same piece of vero board. I will eventually swap it out for a PCB when I get round to it.

I still haven't got to running it through a pair of amps switching full load yet ( too scared! ) but it all works as it should and switches both signals.

Materials:

  • JZC-22F 5VDC and DS2Y-S-DC5V relays
  • 18g alloy folded and welded chassis
  • Resistors from eBay user abillionstore
  • Schematic from Aiken Amps
  • Components from Jaycar