KIT AVAILABLE !!! All In One PCB Kit to sell !!!

[slayer666]

And if you touch pins 1,2,4,5,12,13,14,15 on the muxes with a screwdriver or something metallic, do you see signal only on one channel or on all 8 channels?

I see activity only on one channel If I touch the suggested pins.

If I touch pin3 on any mux I see activity on all 8 channels.

[Synthex]

If I touch pin3 on any mux I see activity on all 8 channels.

It is normal ... pin 3 is the output of mux ...

[slayer666]

If I touch pin3 on any mux I see activity on all 8 channels.

It is normal ... pin 3 is the output of mux ...

ok, but can you reproduce my "problem"?

Only 1 piezo attached
only lcd
No keyboard.

Megadrum Default settings.

[denis]

I have a the same problem with slayer666. I conencted one piezzo to kick input the others are empty and when i hit it there is no problem its tracking ok the low and medium levels. But at hard hits it goes to max value and i see signla on other channels to.
And an other problem I connected hit-hat control pot with kick piezzo and when I set the pot to max value kick channel starts to send continous low-level midi signals.

[slayer666]

I have the MAX4558 muxes on my board, Do you have those also denis?

I wonder if 74HC4851 have this problem too..

[denis]

Yes I have the same kit. I have bought it form synthes too.

[Synthex]

I have not noticed this kind of problem.
I will do more tests.

[slayer666]

I have not noticed this kind of problem.
I will do more tests.

Set it up just like I explained and use default settings. I used a piezo with wires connected directly to inputs.

Here's what admir wrote about a similar problem that only crosstrigged the next channel:
"I agree with you, there must be some differences between 4051 chips from various vendors, as I didn't noticed this failure in my lab, and I tried to reproduce it. It seems to be an overlapping problem, ie. a part of the voltage from previous channel is carried to the next, probably due to different output impedance between direct 324 outputs (channels 1..7) and 4051 output (rest of channels).

I can relax 4051 timings, that's not a problem, just need 1 of those multiplexers to fail I pushed those timing to the max of ST specs datasheet (manufacturer of 4051 I used), but it can be tweaked further I suppose..."

[ignotus]

Hi

I'm using standard 4051's and the diode arrays, and I initially had the same problem. What kind of pads are you using, are they DIY? seems that some DIY pads are a little too "hot" - the way I overcame this problem (signals that seem to "spill" over into other channels with hard whacks) was throwing in trimpots and adjusting them so max levels aren't so high. It might be something else but this worked for me.

[dmitri]

If the pads are too hot there might be a problem with MUX IC "saturation" and as ignotus said the best solution would be to put a trim pot between a sensor and an input to limit input signal. Having said that, you may try this firmware

megadrum32_20_32_20080309.hex

It may fix the problem of over spilling or or it may not. But if the input signal is too hot you will still loose dynamic range.