Drum Master

DIY Electronic Drum Brain

 

Assembly

This page includes some suggestions and notes on how to assemble Drum Master. This is not neccessary, as most people with some electronics experience could assemble everything given the schematics. However, it may contain some suggestions which, while optional, may help make a better project overall. If anyone has any extra suggestions which they would like to be included, please contact me.

Order of Soldering

I recommend that you solder the passive components first, to reduce the risk of overheating and destroying the more sensitive components such as the diodes and ICs.

Grounding Jumpers

You have probably noted the two-by-four pin headers on each group of channels. One side connects to GND, and the other connects to the input channel. Why are they here, and are they needed?

Well, in earlier designs I had problems with interference and crosstalk between channels. This would manifest itself when a given channel, with no pads connected, would send a signal when another pad was hit. In this early design, I found that by grounding unused channels, crosstalk could be minimized.

Since that time, I have modified the filter and amplification circuits, which appears to have completely removed this interference. However, I kept the jumpers in place 'just in case', even though to date I have not needed to use them at all.

You can probably not even put the jumpers on at first (saving a couple of dollars and some time); if you notice any crosstalk with unused channels, you can perhaps put them on later. If you find that you do need these, please let me know; if nobody uses them, I may remove the pads in future revisions.

Filter Resistor Sockets

While it is possible to solder the Op Amp gain and filter bleed-off resistors (RR4 and RR6 in this diagram) directly to the PCB, I have found that you are better off to use a SIP socket, such as Digikey part #ED7150-ND. This allows you to get an even greater range of configuration when selecting pads. For instance, I have found that some of my pads send a stronger signal than others. While the potentiometers allow for quite a bit of range in sensitivity, on my ride cymbal I found it useful to change RR4 to 5k (thus providing up to 40x gain, instead of 10x), and also changed RR6 to 3.3k (decreasing the time during which the pad reports a hit). While this is by no means needed, it does give more configurability.

Going along with that, if you choose to use a SIP socket, I would recommend that you purchase a small collection of 6 pin bussed resistor arrays. You can get 10 of them for about $2 at Digikey. I personally bought extras in the 1k, 3k, 5k, 7k, 10k, and 20k ranges. This provides a good number of substitutes for RR4 and RR6, and can give you a wide range of configuration options.