www.megadrum.info

Hi, this is mainly a question for Dmitri:

Will I damage anything if the input voltage is 5.1V? I ask because I'm looking at power banks to power the module and in the specs some of them say the output voltage is 5.1V.

I was thinking about just running the data lines of the usb cable from MD to the PC and powering the module off one of these power banks (those things for charging phones) to avoid random triggering of inputs due to a "dirty" household electricity supply. Is this a bad idea? If not, what current does the module draw, more or less, so I can have an idea how long it would last powered with one of those things?

You can use a power supply up to 6V. This is maximum limit for HC4851 ICs used in MegaDrum.

If you have a nearby electomagnetic noise source then even with a good power supply MegaDrum may pick this noise up on inputs.

Ok thanks, I'll probably try this out. I've never had random triggering with a laptop on battery power so I reckon the problem is with the household mains supply. Thing is, I prefer to use my PC as it has more horsepower than my laptops, which are either a bit old with short-lived batteries or not really powerful enough for VSTs.

I'm (wildly) guessing MD only draws about a couple of hundred mA with a 2.8" screen (screen draws about 100 mA), so a 16,000 mAh power bank should last a considerable amount of time between charges.

Did you try an UPS/Surge protector with your PC?

No, but I'll probably get one in the near future; not only to try and solve the problem with MD but also because the trip switch often goes off in my home due to too many appliances plugged in and I sometimes lose stuff I'm working on with the PC (apart from sudden power outages not being very good for PCs).

However, Kabonfaiba mentioned in another thread that despite having such devices he was still having this problem with random triggering, which led me to think of a way to power the module entirely separated from the mains supply while still using my desktop PC. If the UPS doesn't do the trick I'll probably try the power bank idea, as I'll also be getting one anyway.

There are different types of UPSs. There are those which isolate powered devices from mains completely.

I read one of the Megadrum schematics briefly, I noticed all the inputs are grounded to pin 40?

As an experiment, could I lead a wire from this ground loop to, for example; the USB connector housing?

That way at least Megadrum would be grounded to my PC through the USB cable, or is this totally unnecessary?

The thing is, I have already covered the inside of my ABS unit with aluminium tape, for additional shielding against external EMI/RFI sources, and yet I still get the odd trigger spasm from a number of inputs.

I'm lead to believe there might be an internal build up of static, on the inputs or the PSB that isn't being grounded. I don't know if there's any other pin on the main PSB or PS board that I could try leading a ground wire from, and connect it to my aluminium layer possibly.

Kabonfaiba wrote:I read one of the Megadrum schematics briefly, I noticed all the inputs are grounded to pin 40?

As an experiment, could I lead a wire from this ground loop to, for example; the USB connector housing?

That way at least Megadrum would be grounded to my PC through the USB cable, or is this totally unnecessary?

The MD board is already connected to the PCs ground via the negative wire of the USB cable.

Kabonfaiba wrote:The thing is, I have already covered the inside of my ABS unit with aluminium tape, for additional shielding against external EMI/RFI sources, and yet I still get the odd trigger spasm from a number of inputs.

Is this tape connected to the MD board ground? I think it should be for the best effectiveness.

Kabonfaiba wrote:I'm lead to believe there might be an internal build up of static, on the inputs or the PSB that isn't being grounded. I don't know if there's any other pin on the main PSB or PS board that I could try leading a ground wire from, and connect it to my aluminium layer possibly.

Ok, so the aluminium isn't grounded. You can connect it to one of many points - I reckon the easiest is to connect it to any of the jack sleeves.

Have you tried using a laptop on battery power? It doesn't even need to have a VST, just plug the module in, fire up MDM and the midi log, and leave it for a while to see if those spasms still occur. I get zero on battery power, which leads me to conclude that the power supply is the culprit. First I'll try with a UPS, and if that doesn't work, I'll power the module off a power bank.

Ok, so I bought a UPS, of the 'line-interactive' type. I know there is an even better system but my budget wouldn't go that far. Anyhow - I still get the random triggering. I guess the UPS filters out any surges that could be hazardous for equipment but small ripples still get through. I do think it happens less often (left MD on for a whole morning and it happened 3 or 4 times), but I would like to get rid of it altogether, so the next step is to get a power bank and power the module from that.