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Guitar Volume Loud/Soft Foot Pedal


The finished volume pedal

The finished volume pedal

Altering an electric guitar’s volume from soft to loud can be accomplished in several different ways, varying from using a switch on the guitar itself through to using an amp with a dedicated drive section controlled by a footswitch. The trouble I have is that the use of several guitars (including electro-accoustics) and amplifiers means that there is no consistent means at my disposal. I’ve been promising to build myself a simple footswitch-controlled volume pedal for a long time and finally bit the bullet.

Normally such a small project would be housed inside one of the many different small diecast aluminium box known and loved by electronics experimenters for years. After discovering that the size I wanted was going to cost about £8.00, I decided that an alternative should be sought and a forage in my local builders suppliers (Wickes) turned up suitable steel boxes available for under £1.00. I refer of course, to the steel boxes normally embedded in your wall to host a 2-gang mains socket. The nominal dimensions of these is 132mm X 72mm X 35mm. They contain various part-punched knock-outs, are made of mild steel and are very strong – suitable indeed for a floor-based unit.

The circuit shown below is hardly ground-breaking, but does everything I want. A pre-set proportion of input signal from the guitar can be set up on the pot., whilst switching between this and the full guitar output is carried out with the footswitch. Use of the metal box, together with screened cable for component interconnection keeps hum and noise to a minimum.

Diagram

Diagram

It dosn’t get much simpler than this!
Parts list:

  • 1 X 1-Mohm log pot.
  • 2 X 1/4inch mono Jack sockets
  • 1 X DPDT (Double-pole double-throw) footswitch
  • 1 X Control Knob
  • 400mm screened hook-up cable
  • 1 X 2-gang electricians metal back-box
  • Aluminium scraps for Jack panel and box bottom
The photo opposite shows the position of the components. I opted to use the ‘bottom’ of the box as the top and opened up two of the centrally placed existing holes near each end to mount the footswitch and volume control. On the side nearest the volume control I removed two of the knock-outs, and used the exposed holes as a drilling guide for a small aluminium end panel, which was subsequently screwed to the end and has the two jack sockets mounted on it. Ensure you have enough space for the volume pot and jack sockets – my fitting of these was a little on the tight side.

Wiring should commence by fitting a solid wire into the brass terminal supplied in the box, (normally for an earth wire) and wiring this to the chassis-bound connections on each Jack socket and earthy-end of volume pot. I then used 4 small lengths of screened cable to connect the sockets, pot and switches as shown. Note – only one end of the screening on each cable is needed – I’ve insulated the ends of screening where the cables join the footswitch.

Internal Wiring

Internal Wiring

Top panel layout

Top panel layout




I used ‘Front Designer 3.0′ to draft this simple top panel, and a PDF document of this image is available here: GuitarVolSw.pdf

I printed out the panel on 100gm paper and laminated it to produce a simple, but servicable panel.
Bottom Cover

Bottom Cover


I re-tapped the holes in the fixing lugs M4, rather than have to buy the fine-threaded electrical fitting screws, and cut a piece of aluminium as a screen for the bottom of the unit. You could mount 4 feet on this – I didn’t bother.
The photo below shows the box before drilling. The brass earthing terminal can be seen clearly at top-right.
Box Interior before drilling

Box Interior before drilling


Note the two different knock-out sizes on the left end of the box. The right-end has knock-outs both of the same size.
Box ordering details

Box ordering details


I got my box from Wickes – these are currently available at just under £1.00 each if bought singly, or just under £4.00 for a pack of six.
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