DIY piezo wiring

[bcslaam]

Sorry for disappearing..holiday season

Yes so I soldered a 50k variable pot inline with just the centre piezo (ceramic centre>in pot middle terminal>out pot left terminal>jack tip) like dmitri has specified (not like the diagram above...yet) and whilst turning it from min to max the effect isnt obvious. There is no effect on the apparent gain, doesnt make it louder or softer but the range does subtly improve when turned all the way down. I wonder if I needed a 100k pot. I thought turning all the way down would cause it to stop triggering no matter what k value the pot is, ie below threshold or something but no...Am I doing something wrong? Would it be different if I used those smaller trim pots? Do they do different things?

[dmitri]

Wiring in the first post is not right. Piezo wires must go to the left and the right pins of the pot. Jack's sleeve must be wired to the left pin and the jack's tip must be wired to the central pin of the pot.

[bcslaam]

In other words each piezo has its own pot and there is no way to wire it using one pot? This is still unclear to me.
I'll draw it. Please confirm this is correct.

edrum piezo wiring 1.jpg

I have assumed that the choice of outside terminals on the pot is arbitrary. As long as the source and destination is correct. I have colour coded it so that if there was no pots in the circuit the colours of the wires would match up.

[ignotus]

The choice of the outside pins just determines the direction you want to turn the pot. Assuming the pots are with the shaft facing you in your picture, the pot on the left will increase resistance with anti-clockwise turns and decrease with clockwise turns - it's up to you how you want to use it. I'd just wire the piezo on the right in the same way as the one on the left, not a mirror image - you have it with the piezo polarity reversed and when you turn it, the rotation direction will be the opposite to the other one.

I'm pretty sure you can't wire 2 piezos through one pot. I you have 2 signals coming through the pot's middle pin, how can the module know which pad you hit? It's not going to work.

[bcslaam]

OK thanks ignotus. Yes pot shaft facing you. Like this then?

edrum piezo wiring 2.jpg

[ignotus]

That'll work; you've still reversed the right hand piezo's polarity (swapped ceramic and brass around), though I don't think it matters with the Megadrum module.

[bcslaam]

Yes! funny you say that because how I've drawn it what Ive read dmitri say you should do somewhere here. Am I mistaken? It would also make more sense to me if, for the rim sensor, the ceramic went to ring and brass went to sleeve. ie reverse the polarity as you say.

Is it different for a snare with PS as opposed to a tom dual trigger?

[ignotus]

PS requires a positive first half-wave for the head piezo but if you have the PS add-on board it doesn't matter how you wire it. Same goes for tom inputs, with or without PS. In short, just make sure the inputs you want PS on go through the PS board, and you can wire the piezos whichever way you want. It doesn't matter either with inputs without PS.

[bcslaam]

For the sake of having a correct diagram available to others (because I couldnt find one anywhere in that configuration) would a more compatible version then be to reverse the polarity of the rim sensor for those with an older unit that doesn't have a PS board? I have that board BTW and I thought PS was available from inputs 2 - 30 in my unit (check my sig) since thats what MMD shows. What inputs are PS with the ARM MD?


I'll report back once I've corrected my wiring and tested.

Cheers

[ignotus]

It doesn't matter, regardless of the module model you have. The polarity is only important if you're trying to get PS to work without the PS board. And even if you wire ceramic to tip and brass to sleeve, there is no guarantee that the first half wave will be positive, as polarity may differ from piezo to piezo and is also dependent on how the piezo + cone assembly is physically built. If attempting to get PS to work without a precision rectifier (the PS board), you'll need an oscilloscope to check the polarity. The PS board is there to provide the positive half wave no matter what, that's all. As for which/how many inputs are supported, I don't know (I just built a precision rectifier myself for one input, the snare), and it isn't really relevant yet, as current VSTs only support PS for the snare and ride for now (those that even support PS), and PS for cymbals doesn't really work with MD at the moment at that. If in the future VSTs support PS for toms you'll have support for it, but for now it's not really relevant.