www.megadrum.info

Here's the tutorial on how I got rid of the hot pad problem.

I had to split the file to be able to post it. 256kb/file i maximum size.
All 3 files needed to unpack.

What is a Hot pad?
I want to see how you did it, even I don't know what you're talking about. Lol

Juze wrote:What is a Hot pad?
I want to see how you did it, even I don't know what you're talking about. Lol

A Hot Pad is a drumpad that has an output signal that's too strong.
A "hot" signal causes overspilling internally inside the muxes, and when that happens on any of the mux inputs you get midioutput from all pads connected to that mux.
You can recognize overspilling when you strike the pad hard and the megadrum registers a hit on 8 channels at the same time.

I hope I did a good job explaining.

slayer666 wrote:Which trigger method are you using?
I had them problems too and instead of adding a resistor or a pot,
I changed the way the piezo was placed and the size (I went from 35mm to a 20mm piezo).

As soon as my wife gets home with the camera I'll show you how I did it.

\m/
Slayer666

I have hot pads. I'm using roland type mesh design with a crossbar running through the middle of the shell. I'm also using 20mm piezo mounted dead center. I only encounter overspilling when I hit the pad dead center of the piezo.

I'm not encountering this with 22 channel input version using the 4051 ICs but I do get overspill with Synthex' design using MAX4558 ICs.

BTW, were you able to use your roland CY cymbal pads?

estregan wrote:

slayer666 wrote:Which trigger method are you using?
I had them problems too and instead of adding a resistor or a pot,
I changed the way the piezo was placed and the size (I went from 35mm to a 20mm piezo).

As soon as my wife gets home with the camera I'll show you how I did it.

\m/
Slayer666

I have hot pads. I'm using roland type mesh design with a crossbar running through the middle of the shell. I'm also using 20mm piezo mounted dead center. I only encounter overspilling when I hit the pad dead center of the piezo.

Ok, Here's how I did it:
partlist:
5 Remo practice pads
2 IKEA round mousepads
5 piezos 20mm diameter

1. Remove the fabric on the topside of the mousepads.
2. Glue the mousepads together using a contactglue (elastic). The double mousepad should be approx. 9mm thick.
3. Make a puncher (I think it's called that) the same diameter as the brassdisc on piezo and another puncher the same width as the ceramic on piezo.
4. Stamp 5 discs of each size.
5. Solder the wires on the piezo
6. Apply the 20mm disc on the brass side of the piezo using thin doublesided tape
7. Apply the small disc to the ceramic side of piezo using thin doublesided tape (Tape on both sides).
8. Place the piezo brass side up 3mm from the rim, Not dead center.
9. Now put the thing together again and you're done.

Estregan, I assume that you're using drumshells so you might have to adjust the placing of the crossbar to make the new piezo reach the mesh.

No hotspot anymore!!

Ps. I'll return with pics soon.

I'm afraid, I can't redesign my pads since I'm also using them with my TD12 at the moment. I'd rather find a way to use them as is.

estregan, as I said before, there is no magic here. If a signal is too strong I cannot do anything about it in firmware. The only way around it is to weaken the signal either electrically with a voltage divider or mechanically as slayer666 did. Do you see any other way?

I have done more testing with the 74HC4851 and the MAX4558.

With the 74HC4851, there is no overspilling even if the signal is too strong.
74HC4851 appears to be better if you have hot pads ...
But, with hot pads, you lose dynamic range !
The better way is to use a trimpot directly soldered on the output jack of the pad.

slayer666 wrote:8. Place the piezo brass side up 3mm from the rim, Not dead center.

So it is similar approach as in Roland PDX8, although mesh piezo is much further from the rim in the latter because of "separation zone". Great to hear it really works:) Do you think that it is possible to have working rim without such separation?

jerzy wrote:

slayer666 wrote:8. Place the piezo brass side up 3mm from the rim, Not dead center.

So it is similar approach as in Roland PDX8, although mesh piezo is much further from the rim in the latter because of "separation zone". Great to hear it really works:) Do you think that it is possible to have working rim without such separation?

I think you're talking about the way the piezos are connected. head piezo - on ceramic and rim piezo - on brass.



I have both piezos setup the same way (+on ceramic) and it works well anyway.