For around £10 you can build a drum trigger pad system that will work with virtually any drum machine or MIDI converter that has drum pad inputs. Paul White shows you how.

I'm one of those drum machine users who never learns to programme the things — I do all the work on my sequencer and simply use the drum machine as a source of sounds. When the Alesis D4 came along, I bought one straight away, simply because I resented paying for an on-board drum-sequencer that I wasn't using. And, entirely off the record, I'm very pleased with it.

Banging in drum sounds from a keyboard is fine for straight-ahead pop songs, but when it comes to trying to put a tasty drum fill together, find my fingers fighting for the same space on the same key at the same time! Drum pads are the obvious solution, especially as the D4 has 12 pad inputs, but if you only use them infrequently, the cost may be too high to justify. However, I didn't study electronics for nothing - it just seems that way when I look in my pay packet! A little research and experimentation produced the following design, which can be assembled by anyone capable of soldering a couple of wires onto a jack socket and opening a tube of glue. Apart from the obvious attraction for the recording musician, the trigger pads also make an ideal, low-cost school project for use in the music department.

Pickup Pointers

The key to the system is the transducer and the way it is mounted — the one I used was the Maplin piezo transducer, part number QY13. These are available for the princely sum of 28p each, and you'll also need some jack sockets, which Maplin supply under part number HF90 at a unit price of 38p. (Maplin (Contact Details)) There are six drum pads in this design, but there's no reason at all not to incorporate more if you need them. These may be made from plywood covered in rubber matting, but being a trifle lazy when it comes to sawing up wood, I bought a set of six melamine-topped drinks coasters instead — hence the number of pads.

The piezo transducers are supplied as coin-sized disks with a couple of flying leads attached to them, and they are fixed, using silicone rubber adhesive, to the side of the coasters depicting wild flowers/cuddly kittens/rustic country scenes. Silicone rubber adhesive can be purchased from any hardware shop and smells strongly of vinegar, due to the acetic acid content — use it in a well-ventilated space, as recommended. I found that the best way to fix the transducer was to squeeze a pea-sized blob of the silicone rubber onto it, then push it onto the coaster until there was a layer of silicone rubber about 1mm thick between it and the melamine surface. This thin layer of silicone rubber protects the piezo transducer from potentially damaging shocks and also reduces the sensitivity to a more manageable level. Pieces of thin rubber mat are fixed to the cork side of the coaster using ordinary contact adhesive such as Evo Stik or Bostik, at which point the pads are ready to mount.

"Banging in drum sounds from a keyboard is fine for straight-ahead pop songs, but when it comes to putting together a tasty drum fill, I find my fingers fighting for space on the same key at the same time!"

The pads may be fixed to a common wooden base, but in order to prevent one pad from triggering another, they need to be isolated from each other by means of foam rubber or neoprene foam. All the pads may be mounted side by side on a single sheet of foam (double-sided carpet tape is ideal for this), and the leads threaded through holes in the base board where they are attached to the jack sockets. A spacing between pads of 10mm or so is fine. There is no electronic circuitry at all — the wires on the transducers are simply soldered to the jack sockets, though some may need to be extended in order to reach. I cheated by soldering the leads to drawing pins stuck into the underside of the base board and then soldered wires long enough to reach the jack sockets to the drawing pins.

Figure 1 shows how the prototype was assembled, including details of how the transducers are wired to the sockets. The wooden base is fitted with four sides which serve to hide the wiring and provides somewhere to mount the sockets. This may be placed on any flat surface when in use, but if it is intended to use the system in a live situation, then I'd recommend that you fit a wooden base and bolt on a stand adaptor, to allow you to position it at the correct playing angle.

The finished unit may be painted, but I opted for staining the wood and then polishing it with Briwax, a product available from most large hardware stores that, with about the same effort as polishing a pair of shoes, produces a finish that most people can't distinguish from antique French polish.

Hitting It Off

Using the pads with a D4 requires only that the trigger inputs be assigned to the requisite sounds and that the trigger gain be set up so that you get a reasonable dynamic range from the pads when playing normally. I found a gain setting of around 50 about right, but you really need to set it for your own playing style. Most other trigger-to-MIDI converters have some means of adjusting the sensitivity, and you should find this pad system gives out a similar signal level to other electronic drum pads.

There is no reason for you to stick rigidly to the design presented here; a possible variation is to use pads of differing sizes with, say, a large pad for the snare and toms where you're more likely to want to play double-handed rolls, and smaller pads for cymbal and percussion sounds, where you're more likely to play one-handed. You can also use these transducers directly on acoustic drums to trigger samples via a pad-to-MIDI converter or MIDI gate. And at 28p each, it doesn't matter too much if the drummer writes the odd one off!