Hi NYMO,
I would recommend only the conversion of a tom module to an analogue HH. Short description: There are 2 different hihat modules (mostly not) available: The analogue from music aid era and the digital. They both use the same pedal, take a look at it at simmonsmuseum.com. The pedal contains an infrared coupler, giving a trigger pulse to the modules input (you see the white writing "Hi-Hat Trig in" printed on the surface of all pcbs). It also cuts the decay of the enveloppes when beeing closed. You will need some additional parts: On the original HH pcbs the additional parts are located in the middle of the board (on the other boards there is this empty spot near R46). These parts will become the control of the hihat. You can add the missing components easy, you drill some 1mm holes, add the parts and solder them together. Then your module will act as a hihat - but: You have also to alter the sound generator for original simmons SDS5 analogue hihat sound.
The analogue hihat module has an LFO fitted like the snare. If you pitch this high, you get a ring modulation (in conjunction with the VCO) and it sounds some kind of metallic. Also noise must be fed from the noise source's output via a resistor on the solder side of the module to the VCO's control input. The result is a waveform like a metallic pan-flute (difficult to describe). But the sound fits very good to the other analogue modules. So: you need some 10 electronic parts (around 2 dollars) and a pedal. Another dollar for the parts to fit an LFO, if this is missing. You see, it is very easy and cheap to convert a module into an analogue hh. The only person I know possessing an original analogue HH is
devo@.... On his page you find also one of my essays changing an SDS7 module to HH and there is the description how to change an ordinary Roland Pedal or an e-piano pedal for Simmons use, it works with SDS5 HH too.
The digital HH has a small piggyback pcb containing a forward/backward counter and a 2732 eprom providing a metallic waveform. Simmons were the first to have a forward/backward loop in the synth history, I guess! This waveform is fed into the modules VCAs instead of the VCO. To change a tom module to a digital hh, you need this piggyback board or somebody constructing a copy for you. I never did it, it must be possible but I don't think it is easy.
The cymbal is also tricky. I never heard about an analogue cymbal (I think there was no), so I can only describe the digital one. This has the same piggyback pcb as the hihat, but there is also the rectifyer trick: The original cymbal (riot shield plastic) pad has 2 zones, bell and cym. It has 2 trigger piezos, one for each zone. The cymbal pad has 2 diodes and a capacitor, so a hit on the bell creates a positive phase, a hit on the cym a negative. So you can trigger 2 sounds via one XLR line on one module (if you are lucky. There is much crosstalk). If you play the cymbal module with a normal pad, you have no bell sound. So: Changing a tom module to a digital cymbal is really difficult, because you have to change a lot of circuitry on the main board of the module. You need the piggyback board too. Digital cym and hh have also up/down bend, so this has to be changed on the tom module too.
Cheers too.
Michael
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