Bass drum phantom triggers, increased performance on midi

[protone]

I am using a Roland TD4KP hooked up to a midi interface. I have experienced a lot of false or phantom triggers. This means there are notes played which I never hit. Usually the phantom notes are played at a very high velocity, much louder then all other notes.
In the internet are a lot of explanation's about this mainly related to USB cables. But how can cables influence one instrument only? This seamed not logical to me. So I did some research on this issue and came up with a surprising answer.

This is my finding: The kick pickup and the beater are electrically charged when they separate. This electrostatic voltage can reach several thousand's of volts. If the charge is high enough, there will be a discharge on the pickup. This will cause a false trigger. If the voltage is high enough a discharge can also cause midi communication errors. This shows in repeating the last played notes, or other very strange effects.

If you want to know more about it and see my solution please watch my video on you tube:

https://www.youtube.com/watch?v=avNi8TCe6qc

The overall performance of the bass drum is so much better now, it just feels great.

Please let me know if this has helped you.

[MS-SPO]

Well done ; -)

[BarT]

Thanks for taking the trouble to educate us all about this phenomenon.

Would an alternative solution be to earth the beater shaft somewhere?

[protone]

My solution is a fast fix. The really professional solution (as I expect it to be done by Roland cooperation) would be to use dissipative materials. This means the material should not charge and must have electrical conductivity. Than it would also make sense to earth or at least having a common ground on the shaft and on the pickup. You can earth the shaft after the aluminium foil is fixed. But I do not expect a significant improvement since the beater is not charging anymore with the foil.

Thanks for reading my post.

[MS-SPO]

Would an alternative solution be to earth the beater shaft somewhere?

No, if the hardware is as protone showed. There I saw an insulating cone (left side) and a beater made from insulating material (right side). The charge separation happens, where cone and beater come together. As the beater does not conduct current, that charge can't travel to the beaters shaft. So putting the shaft to ground or not doesn't make a difference.

That's why protone wrapped everything in a thick aluminum foil to establish one (larger) conducting surface. Making the beaters contact area with the cone more conductive AND connecting it electrically to the shaft would have been sufficient ... unless ...

If protones kick pedal is not electrically grounded than all what happens ist to replace the former capacitor (cone - beater) by one with a higher capacity (cone - wrapped beater). If you remember, C = Q/V, then V = Q/C. So if the charge Q remains more or less constant (through kicking) AND when the capacitor C increases, THEN the voltage drops (by the caps-ratio). Now protone's video shows a much higher reduction in voltage, which means, his kick pedal probably is grounded good enough.

To indicate without grounding the voltage would drop by the ratio of both capacitor values (wrapped vs. unwrapped). This is roughly the ratio between the beaters contact surface and the whole surface of the wrapped device. Unless the contact area is very very small, this ratio will be in the order of, say, 1:10 or 1:20, while the video shows voltage reduction of about (1 V) : (1000 V).

Best, Michael

[djska]

Try soldering a 10Meg resistor across piezo or jack output to prevent the build-up of static

[protone]

I am working with machines for semiconductor industries. Electrostatics is a big issue on this machines. To solve these problems we have to use the correct materials.
If we have materials which cannot be replaced by dissipative or conductive materials we are using ionizers. A Resistor connected to an isolator will have no effect.
If you would like to find out more about ESD go to Electrostatic Discharge Association (https://www.esda.org/)

But in the case of this bass drum issue the solution with aluminium foil is simple and works perfect.
The real professional t solution would be to use dissipative materials on the pickup and the beater. This can only be done by the manufacturer I think.