Overspill?

[denis]

Istanbul-Turkey

[dmitri]

I've done some testing with MAX4558. It appears that even if the the signal is not too hot, negatives half waves cause troubles with piezo/switch type pads. Without a negative overvoltage protection like this:

MAX4558.png

switch channels of piezo/switch pads falsely trigger on piezo only hits. To eliminate 'overspill' effect a positive overvoltage protection is also required thus making MAX4558 not much better than regular 4051 ICs.

[Synthex]

There is no problem with the 74HC4851.

It is better to use the 74HC4851 that the MAX4558.

[Beamtreetaker]

Hmm, that's bad news for me as I'm using the MAX chip. Can you tell me where I can find the 74HC4851, I did not yet find any online shop selling it.

[Synthex]

Hmm, that's bad news for me as I'm using the MAX chip. Can you tell me where I can find the 74HC4851, I did not yet find any online shop selling it.

I can sell you 4* 74HC4851.

[Beamtreetaker]

Okay, thank you Synthex. A friend of mine is thinking about buying a PCB from you soon, so we will put our orders together maybe. Or- do you know how much shipping to Germany for just those 4 chips would be?

[Synthex]

For all those who have already bought a kit from me, with only MAX4558,
the 4* 74HC4851 chips are free

Only shipping must be paid.
- by Registered Airmail anywhere in the world (signature required) = 9 euros
- by Regular Airmail anywhere in the world (no claim will be possible to transport problems) = 4 euros

Synthex

[japi]

2. You can quite easily test if the pad is too hot (signal from a piezo is too strong) for MegaDrum. Set "HighLevelAuto" to Yes and hit the pad as strong as you consider a strongest hit you normally do. Then check what MegaDrum shows in "HighLevel" for this pad. Is it more than ~900-950? If so, and "Gain" for this pad is already set to zero, than the pad is too hot and you're loosing dynamic range. You either need to put a trimpot for this pad or dampen the piezo.

I have done this test today and my pad has a HighLevel of 1002.
Please theres a schematic or picture on how to put the trimpot on the pad ? Which value trimpot?

Thanks

[dmitri]

Disregard everything connected to Ring.You can use a 15k-220k pot in place of 220k in the schematic. You don't need the 10k resistor and the 0,1uf capacitor and can replace them with wires.

[dmitri]

Btw, you did try to lower gain levels, didn't you?