Overspill?

[Synthex]

So you have DIP-16 package version? Where did you bought it?

Yes, I have the DIP version. I bought it in France in large quantities for my kits.
I can sell you some parts if you want.

[jerzy]

Thanks for the offer, but it just started working somehow. I really don't know what was wrong, but it (almost suddenly;) started to work now, according to LED (I unnecessarily unsoldered one of MPXes, but now I know it's possibile to safely resolder SMDs without special tools - just soldering gun and screwdriver:) . One thing I'm afraid now, that MD is too sensitive - it senses even gently touching cable near piezo. Is it normal?

[elrules]

I have the doubt now if I must build the first Synthex PCB version, with diodes and resistors, or the new one... I don't want to build it and suffer the overspill issue (cause I don't want to add pots). So, are you completely sure that the problem is the MAX chips? Will the 74's work as well as the resistor-diodes version?

[Synthex]

Thanks for the offer, but it just started working somehow. I really don't know what was wrong, but it (almost suddenly;) started to work now, according to LED (I unnecessarily unsoldered one of MPXes, but now I know it's possibile to safely resolder SMDs without special tools - just soldering gun and screwdriver:) . One thing I'm afraid now, that MD is too sensitive - it senses even gently touching cable near piezo. Is it normal?

Yes, this is normal.

[Synthex]

I have the doubt now if I must build the first Synthex PCB version, with diodes and resistors, or the new one... I don't want to build it and suffer the overspill issue (cause I don't want to add pots). So, are you completely sure that the problem is the MAX chips? Will the 74's work as well as the resistor-diodes version?

Yes, the 74HC4851 work as well as the resistor-diodes version !!

[Synthex]

4x SN74HC4851N :

SN74HC4851N_low.jpg

[jerzy]

I have the doubt now if I must build the first Synthex PCB version, with diodes and resistors, or the new one... I don't want to build it and suffer the overspill issue (cause I don't want to add pots). So, are you completely sure that the problem is the MAX chips? Will the 74's work as well as the resistor-diodes version?

Yes, the 74HC4851 work as well as the resistor-diodes version !!

Actually, I'm experiencing some crosstalk even using 4851's and 20mm piezos. However I don't think the dynamic range is limited, therefore it could be caused by electromagnetic interference/induction (poorly shielded cables; although it seems that bypassing piezo with 10k resistors helps).

[dmitri]

1. Are your pads fully mechanically isolated from each other and so you can conclude that crosstalk is caused by electrical interference or overvoltage?
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.

[Synthex]

Actually, I'm experiencing some crosstalk even using 4851's and 20mm piezos. However I don't think the dynamic range is limited, therefore it could be caused by electromagnetic interference/induction (poorly shielded cables; although it seems that bypassing piezo with 10k resistors helps).

4851's is not in question.
What kind of cable do you use ?

[jerzy]

1. Are your pads fully mechanically isolated from each other and so you can conclude that crosstalk is caused by electrical interference or overvoltage?
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.

Ad.1: I don't have real pads yet, so I'm connecting just single piezo.
Ad.2: I'll do it, but I have to read sysex description first or try to run MDC with Wine, as I don't have LCD nor Windows. My current tests were carried out on default settings.