Akai MPC ONE CV voltage humming noise when connected

Any time you see dimmed LEDs there are extremely rapid oscillations taking place which will generate a considerable amount of noise--sometimes it's even audible coming directly from the components themselves without any kind of amplification involved. Hold a remote control up to a guitar pickup and press a button. The exact same thing is happening constantly in order to produce the goofy raver lightshow and if you've ground loop issues in your house plus crap cables feeding into some cheap Behringer mixer sitting next to a Eurorack full of questionably shielded Kickstarter products then you're going to have a bad time. The One lacks XLR outputs so this is a known risk.

Probably this:
https://en.m.wikipedia.org/wiki/Ground_loop_(electricity)

Depends on where in the house your power outlets are and how they are „cabled“. Good indicator for a ground loop is, if humming (with or without overtones, multiples of 50 Hz (Europe) or 60 Hz (US)) appears only when touching some device or when battery powered units are powered with cables. Often the ground loop („Erdschleife“) disappears when using laptops and disconnecting their PSUs/chargers.

I'll throw my hat in the ring and add that I too am getting hum from my SH09 when the MPC cv/gate outputs are connected to it. MPC is standalone but I'm using USB midi. However, it seems to be changes on the screen that affect the hum.

I notice on my MPC One that certain screens cause noise on the outputs too, it is related to (I believe) PWM noise from the LEDs as it is worse when more pads are lit up, for example in the sample edit screen, it is also worse if audio in is being monitored.

Also the USB noise can be dependent on what is connected to the USB port, I plan on doing some further tests to see if I can isolate the problem, I am going to be making a CV junction box for my One to break out the TRS pairs into individual TS sockets and I might try a ground lift switch on the CV outputs to see if it remedies the noise problem.

I will update the thread if I discover anything worth reporting.

Get rid of hum for good:

Compare the sound of your set up by using alternate power supplies, and wallwarts of equal voltage or with a variac.

Use a power conditioner. Dollar store white abs plastic power strips, octo and hex plugs are the devil.

Sheilded trs cables. Ballanced lines are great but with the added sheilding you can be super confident draping it across other cables without it inducting signal from outside sources. If you're using regular TS or RCA cables they will act as rf "inductors" if you leave them draped across powered lines. If they are coiled, its even worse. The diameter in which you coil an unballance line is also the coefficient for what frequency it inducts lol. Dont coil your cables, but also dont drape them on others. Tricky i know....

Ground your devices. you need to find a spot where the circuits ground meets the chassis of your device and some how afix a wire from it back to your sampler in the same fasion.

If you power an external with usb from the mpc and then plug audio cables into the device back to the mpc you just created a loop. A powered usb hub generally corrects this.

Dont use your MPC to power usb devices. If you want audio communication and power, buy a "powered usb hub" with suffucient wattage to power all your devices. Volts x Amps = Watts. Physically read the power supplies for "output" specs and do the math, write it down, combine the tally of all your intended devices and invest wisely in a hub.

Mpc one users can get rid of some hum as well by soldering some extra ground wires with LEAD solder to the ground on the psu. The restriction of hazardous substances compliance means they solder your devices with shit for solder.

“Mpc one users can get rid of some hum as well by soldering some extra ground wires with LEAD solder to the ground on the psu. “

Could you elaborate on this @Ultros ?

Sure, find a good ground on the soundcard and on the psu and add a wire connecting the two. Since the mpc is made up of multiple circuit boards grounding each of the boards back to the psu with some extra love would likely help alot. I dont have any diagrams or photos of "how to". I havent got around to messing with mine yet. Some rf sheilding wouldnt hurt either.

the mpc one chassis is made of abs plastic which is bad for grounding. only the bottom lid part is made of metal and makes contact to a couple circuit board when screwed together.

If you ran a wire from under a screw that holds each board in- to underneath a screw that holds the psu in
I would bet dollars to donuts a lot of humming would be removed. Some screws have a silver ring under them on the pcb, those are your target ground points. just one on each board.

Example of the screws with metal rings under them, and (uart hooked up incorrectly in that photo lol)

Not sure about the suggestions to mod the MPC one.

To start with, Akai need a setting to disable pad LEDs. They're clearly injecting hum.

Akai, are you listening?

did u solve this issue?

Theoperator wrote:Hello everyone, I have this strangest problem. When I connect my MPC ONE to my eurorack with the CV Voltage and Gate patch cables I start hear a humming noise in the background. It disappears when I press the Midi section in the menu, but when I am back in the Audio section to record the sequence the noise comes back. It`s quite annoying because it will ruin the quality of my recordings.
Now I don`t know if it`s something that happends only to me or are there others that have experienced the same problem?
I will apprecciate your opinion in what can be wrong?
Maybe ground looping problems (like the Arturia BeatStep Pro?)

Ultros wrote:Dont use your MPC to power usb devices. If you want audio communication and power, buy a "powered usb hub" with suffucient wattage to power all your devices. Volts x Amps = Watts. Physically read the power supplies for "output" specs and do the math, write it down, combine the tally of all your intended devices and invest wisely in a hub.

Okay. That's why I was getting hum when I powered the Pyramid to the Force, but not when I plugged it into the USB hub or was it the other way around Now I need to test again.