Making A Foot Switch
Switched-on Phil 'the DIY-lithium crystals canna take it, cap'n' Walsh gets pedal powered
It's a sad fact of life that there are quite a few hidden costs involved in buying gear, particularly things like drum machines, echo units etc. One of the most annoying points is the lack of footswitches with the majority of gear. Most manufacturers offer these as an optional extra but they tend to be a bit pricey. Luckily the bits you need to make your own are fairly easy to find and you can make up your own footswitches for under a fiver.
As different bits of gear (even from the same manufacturer) use footswitching in different ways it is important to find out which type of switching you need before you start. The main switching arrangements are:
1. Single switch — push for on, push for off (by far the most common).
2. Two switches — push one for on, the other for off.
3. Single switch — successive pushes for on/off — switch produces switching spikes.
If the footswitch socket is a single, mono jack socket then you need either type one or type three. If the footswitch socket is a stereo jack socket or two separate jack sockets then you need type two.
To sort out between one and three you will need to do a few tests. Make up a test lead by soldering two wires to a standard jack plug. Plug in your test lead. Touch the two free ends together and see if it cancels the effect. (Don't worry about getting a shock — it's very low voltage). If breaking the contact then restores the effect, you need switching type one. If during these tests the effect switched but in an inconsistent way then hold the two free ends together and then rapidly break and remake the connection. This should start the effect and repeating the break and make should stop the effect (type three).
This is generally used for reverb and echo/delay units. Though the switch unit is available from many music shops as a blister-packed accessory, the cost is usually in the price range of £4-£6. Against this the same switch is available from electronics shops for around £3.25. The switch you will need is a Heavy Duty, Metal Button DPDT Footswitch. Strictly speaking you could get away with using the SPST version but the DPDT is more easily found, allows you to use two sets of contacts for increased reliability, offers you the option of adding an indicator light and costs virtually the same. Figure one shows the wiring layouts for the standard footswitch, which has a permanently fixed lead and the footswitch with a built in indicator LED — as the footswitch unit contains a battery it is wired to a stereo jack socket which switches the battery supply off when the connecting lead plug is pulled out. As with all these footswitch units a cheap but robust case can be fashioned from a tobacco tin.
(Yes, I know two comes after one — just be patient).
This type of switching is used on many drum machines as the start/stop. If your drum machine uses a single push button to both start and stop the drum pattern (eg Drumatix) then this is the switch for you. The wiring — shown in Figure three — looks pretty silly, relying on the short switch-off time as the switch blades move from one position to the other.
This type of footswitch can be used on those drum machines which have separate stop and start push buttons. It uses two push-for-on release-for-off switches (at their simplest, two door bell pushes). The lead you use to connect the footswitch to the drum machine can be either stereo coax or three core mains cable. The wiring diagram is shown in Figure Two.
The Boss Dr Rhythm DR110 is a handy little drum machine with one unfortunate restriction as far as some live applications are concerned — it has no footswitch facilities. Fear not — help is at hand. The type of unit you will need is type two but in order to use it you will have to adapt the Dr Rhythm.
In order to protect your 16 user programmed patterns you will need a mains power supply to hookup whilst you do the work. Turn the unit onto its face and remove the three cross head screws which hold the case together. Remove the battery cover and batteries and gently prise the two halves of the case apart, easing the metal battery contacts to allow clearance. Store the three screws and the blue plastic on/off switch button in a safe place and then turn the unit onto its back. Pull off the front panel control knobs and pull the case away from the circuit board. There is room in the case, just below the Accent button, to fit a 3.5mm stereo jack socket. Check the clearance and then drill a suitable hole for mounting this. Care should be taken to buy a socket with a long mounting thread as the case is rather thick. If this is not possible then countersink the socket mounting hole to ensure that the mounting nut does not prevent the 3.5mm jack plug from pushing fully home.
Separate the two circuit boards and look at the back of the board which carries the switch pads (ie the side of the board which was on the inside of the two board "sandwich"). There are very few solder pads on this side of the board so the ones we need are fairly easy to find. On the left hand side of the board (viewed with the wire hinge away from you) is a small rectangular space about ¾"x½"containing a few solder pads. Solder a thin, flexible length of insulated wire to the bottom left pad and another to the bottom right pad. Solder one of these wires to the tip contact on the jack socket and the other to the ring contact on the socket.
Looking again at the back of the circuit board there are three tracks which run from the top to about three quarters of the way down the board, roughly halfway across the board. Solder a third flexible lead to the pad at the end of the centre one of these three tracks and solder the other end to the screen contact of the socket. Carefully re-assemble the unit, remembering to locate the blue on/off switch button.
Make up a switch unit, type two, soldering the 3.5mm stereo jack plug to the end of the lead. The wire which is connected to both switches should be soldered to the jack plug screen (barrel) connection. The Dr Rhythm should operate normally even with the footswitch connected but with the addition that it can be started with a push of one footswitch and stopped with a push of the other. As an added bonus, for those with a weird turn of mind, you can also program patterns using the footswitches.
As before, one final word of warning — this modification will invalidate the guarantee so wait a year after purchase before you do it. Whilst I'm talking about the DR110 it's worth mentioning that the type of circuit board they use tends to be affected by damp. If your DR110 starts doing strange things it can often be cured by drying it out in an airing cupboard fora couple of days. If you're in a hurry a quick once over with a hairdryer often works wonders, though you'll have to open up the case to do it.
Gear in this article:
Feature by Phil Walsh
Previous article in this issue:
Next article in this issue: