www.megadrum.info

Top tip for everybody!

Buy some ferrite beads and put them on your USB cable, if you haven't already done so.

Being that triggering is highly sensitive affair anyway, it could be beneficial to put them on all TRS cables too.

It costs the price of a sandwich to buy a 10 pack of ferrite beads, so there is nothing to lose, only gains.

Proof:




I have simply attached some ferrite beads to the USB cable in this test, and nothing else, the difference is visually obvious.

Link to webm version: https://webmshare.com/play/Qxr9Z

I have been able to reduce thresholds on nearly all my piezo based triggers by 3 to 6 levels.

Now, I obviously have quite a serious issue of noise being ingested somewhere between my PC and Megadrum, which is problematic, yet I have no WiFi or Bluetooth devices connected or nearby, and all my cables are shielded, ethernet networked.

Whatever interference Megadrum is picking up, these ferrite beads reduced it significantly, so it's highly worth just trying this, even if you don't suffer EMI as bad as I do.

That looks like a great find! Much easier and cheaper than a UPS or other convoluted solutions that I've tried and no longer bother using... One question - how big are the ferrite beads you bought? Because they must be fairly large to slip over the USB plug. Also, how did you secure it to the cable? Easy enough to work out myself, but maybe just a picture of your ferrite bead on the cable would be nice. I seem to recall seeing cables inside my PC where the cable is just looped through the bead.

I actually bought the smallest ferrite beads I could find because I went with the theory that I wanted the magnetic field as close to the core of the cable as possible, rather than getting an oversized ferrite bead - and having a stronger magnetic field.



Pictured are beads designed for cable width 3mm - 4.5mm

These are a little small I feel for the USB cables as you can see the clips pinching the wire a bit. I have 5mm ferrite beads coming soon, so I will be using those on the USB leads instead. I will move the 3mm beads to my TRS cables, which are thinner and more suitable fit.

I would love to try a giant ferrite core and loop my USB cable through it 2 or 3 times, as that supposedly increases the suppression effect, maybe I'll order one of those now.

I'm also considering buying some of these miniature cores and getting to work with the soldering iron on all my pins:


There is probably no good reason for doing this, other than placebo effect, maybe I'll see a reduction in crosstalk, but I'm already pleased with the improvement so far!

Great stuff. Those are the ones I've just been looking at. Yep, I think I'm going to copy your idea and get a few of those for the pad leads and a larger ring for the USB cable.
Have the random triggers disappeared entirely with the beads you have now?

Cheers!

ignotus wrote:Have the random triggers disappeared entirely with the beads you have now?

Cheers!

That is indeed the big question! I'm basically waiting for confirmation on this.

It's a problem that happens occasionally at random, at most a couple times over a few hours.

I'm not sure till I get a large EM burst from whatever causes it (I'm still unsure) but I have a good feeling I've reduced it considerably.

Ok, hopefully it does the trick. To do the testing I just left the module on, went about my stuff for a few hours and then checked back on the midi monitor in MDM.

I tried using a power bank or even my mobile phone using an OTG cable to power the module, and the bursts almost disappeared entirely, but for some reason I had to change all the threshold settings in the pads, requiring a different configuration depending on what power source I was using... I'd much prefer to just use the PC's USB power supply and not have to fiddle around with even more accessories and cables, so if this works it would be ace!

Now, to be sure...
Do you use these things on all your TRS-cables, and also on your USB cable? Or only on the USB?

I'm using 3 beads on the USB cable that supplies power (and MIDI) to Megadrum - 2 at PC end, 1 at Megadrum end.
I am also using 1 on all surrounding USB cables also attached to my PC.
I have also attached 1 ferrite bead to ALL my TRS jacks - trigger end currently.

ignotus, I've long thought about designing a power regulator circuit that sits between the pins after the USB input and the main PCB, which I assume would use a series of capacitors. Alas, I have no clue how it would work, I only know words to the degree of "ripple" lol.

Well, I've ordered some on the strength of this thread. Not really for MD but I have both keyboards sending pitch bend info.

This should go without saying, but your mileage may vary.

It is very possible I have exceptional circumstances with EM interference on my PC (it's about 8 years old too) but as I said, these beads aren't expensive.