Problem with my floor tom on input 9

[Andrej]

Built a floor tom (cakepan and cone) and before configuring it I'm using my Oscilloscope to make sure the signal is fine, before moving
on to configuring it with Megadrum.

The tom has a nice signal when connected to inputs #7 (Tom1) and #8 (Tom2). However, when connecting to #9 (Tom3), the signal is
bastardized (see screenshots).

Is this related to the rectifier board? That takes input #4, #6, #8, #10, #12, which are SnareH, RideB, CrashB, Tom1H, Tom2H.

The Floor Tom works fine in SnareH, Tom1H, Tom2H...

The signal I see is crap, doesn't matter if I cool it with a resistor. But, the Megadrum module is turned off, so Megadrum settings should not
be a factor here, right?

[Andrej]

Looks like only my Rectifier inputs work? Here's my Yamaha RHH-135 HiHat. Nice signal in Input#4, bad signal in Input#3.

This is with Megadrum module turned on.

What works well so far:
(1) Snare in Input #4 (DIY cakepan + cone, not cooled)
(2) Tom1 in Input #7
(3) Tom2 in Input #8
(4) RHH-135 controller (polarity switched in module)

So far, anything that uses the rectifier board or the HH controller input works. The rest does not.

[dmitri]

If a signal on an input without a rectifier is clipped around 5V, as in your example, that means it is too hot. You have to cool it down with a voltage divider. Also, negative half waves on an input without rectifier will be clipped to around -0.6V and ignored.

[Andrej]

If a signal on an input without a rectifier is clipped around 5V, as in your example, that means it is too hot. You have to cool it down with a voltage divider. Also, negative half waves on an input without rectifier will be clipped to around -0.6V and ignored.

Ah, ok. Even with a 100kOhm resistor I got almost 6 Volts. Did not expect that I needed more than 100k, so I did not even try cooling it more.

That means I have to cool every pad/cymbal that I connect to a non-rectifier input. Got so used to the rectifier board to do that for me

One more question: Since I set the polarity to positive-first-half-wave, is there any advantage of using the rectifier board at all (besides from
automatically cooling the pads)?

Wonder how that relates to cross-talk... my tom is mounted over my bass. If I kick the bass, I wonder if the xtalk could produce a first-half-negative
wave, that could be ignored without the rectifier, but with the rectifier, it will be recognized.

Now I see the light again. Looks like all my toms produce a nice and clean signal, and once I cool them down (a lot) then Megadrum should trigger
nicely.

Thanks Dmitri.

[dmitri]

One more question: Since I set the polarity to positive-first-half-wave, is there any advantage of using the rectifier board at all (besides from
automatically cooling the pads)?

Positional sensing works best with the rectifier.

Wonder how that relates to cross-talk... my tom is mounted over my bass. If I kick the bass, I wonder if the xtalk could produce a first-half-negative
wave, that could be ignored without the rectifier, but with the rectifier, it will be recognized.

It could be the case but before replying on xtalk suppression it is better to achieve as good as possible mechanical isolation between pads.

[Andrej]

Continued with my PCY-155 and PCY-135 cymbals. The PCY-155 in the Ride input (#5) works fine (Bow, Edge, Bell, Choke).
Then I figured PCY-135 in the Crash input (#6) would be piece a cake. Not so. The PCY-135 always plays the "dampened note", and pressing
the edge doesn't generate aftertouch (because Megadrum thinks the switch is always closed?).

The PCY-155 in the Crash input has the same problem, and the PCY-135 works fine in the Ride input. So, must be something rectifier related again?
I thought both inputs use the rectifier. But looks like the inputs Snare, Ride, Tom1, and Tom2 use it, as those work great.

So, I've set the PCY-135's built-in potentiometer to min, then hooked up the Oscilloscope -- not hooked up to Megadrum. The waveform tops
at about 2 Volts.

Hooked it up to the Crash input, and the waveform is basterdized again.

Do I need to cool a PCY-135 as well, even though its waveform peaks at 2 Volts (with the built-in poti already at the minimum)?

Will get a 1MOhm poti tomorrow and see if that solves it.

[dmitri]

1. Yamaha cymbals are already cool enough. What "basterdized" do you see in the signal?
2. Post settings for a specific cymbal in a specific jack with a problem description.

If MegaDrum thinks that an edge switch is closed, why don't you set Threshold lower on the edge input?
Settings for the same pad/cymbal in an input with and without a rectifier, naturally, will not match even close.

[Andrej]

Ok, Yamaha cymbals all working fine. Making good progress

Now back to Floor Tom on a non-rectifier input. Working on optimizing the pad, and have cooled it with a 47k resistor.
That gives me HiLevel of about 350 at Gain 0.

Connected it to Input 9, which works, but wondering if I can do better.

When hooking up the scope, the waveform looks a bit distorted.

When plugging into a rectifier input, or by not plugging it in at all, the waveform is nicer.

Is this expected? Wondering if I should spend time trying to optimize this further...

Getting rid of false triggers seems harder on this input than on a rectifier input.

[Andrej]

WIth the scope hooked up, I think I can see why I get false triggers. Very often, second half wave is greater
than the first. This does not happen when plugged into a rectifier input.

Fixed this by setting MinScan=40 and Retrigger=8, which is good enough for the floor tom. Tom1 and Tom2 trigger
fine, but they're plugged into a rectifier port.

Is what I'm seeing expected? The rectifier inputs seem to distort the signal much less than the regular inputs. Also, waveform is not clipped at 5V, which is another thing that I expected.

[dmitri]

When hooking up the scope, the waveform looks a bit distorted.

When plugging into a rectifier input, or by not plugging it in at all, the waveform is nicer.

Is this expected?

Yes. These are low impedance inputs with fast sampling. When an input is being sampled, the piezo, a high impedance signal source, is loaded onto a low impedance input hence the seen signal form. MegaDrum only sees the the signal which is loaded with input impedance.

For suppression false double triggering you'd better increase DynLevel and DynTime rather than increasing MinScan and Retrigger.