USB port causes noise

[Jmoss]

I have noticed the low level noise coming from my MODX8 for some time now. Thought it was just noisy but no, when I unplugged the host usb connection from the computer the noise totally dissipated. So I thought maybe my computer was causing the noise but no, when I hooked the other end to anything USB wise the noise came back. Tried different usb cables as well. Same result on everything. Anyone else notice this?

[Saul]

Well you definitely shouldn't be getting any noise through the USB cable. What sort of power outlet is your MODX plugged into? It's possible it is a mains generated noise so I would try a different outlet first and also perhaps a surge protector with noise filter built in.

[parametric]

I'm not sure how domestic power is arranged in the US, but IME, if components of a Sound System are powered from

different PHASES, the result can be a noisy system . . .

Case in point - A studio, where everything was powered in the Control Room. The Mac was located in a "Machine Room"

(to isolate noise from the Fan) and supplied from a different "Phase" . . . Result - a noisy system.

We ran a mains cable from the Control room to the Machine Room to power the Mac - Result - a Quiet system . .

ALL components now powered from the same Phase . . . . .

But you need to check with a local electrician that it is arranged in this fashion in the US. . . .

parametric

[EB5AGV]

Does the USB cable have ferrite filters on both ends?

Jose

[Kal1n_M]

It definitely sounds like electricity problem, either phase issue or ground problem in the PC, etc. I can't see how it could be a MODX problem. Try using a UPS with standard power outlets and run your PC and MODX thru it, check if that helps. I know that fixed a slight hum in one of my HS7 speakers...

[Derek]

Dumb question: is it a good quality USB cable? If you try a different cable do you get the same problem?

[anotherscott]

If your computer is a laptop, try unplugging it from the mains and just running it from battery, that might solve it. Unlike 5-pin MIDI, USB MIDI can be susceptible to ground loops. (I remember reading that some people have also solved the problem by modifying their USB cable.)

[Davelet]

It's a common problem, if you do a bit of google searching. What do you have connected to the output of your MOXF (i.e., the main Audio outputs)? Is it a mixer with inputs from other audio sources? Does disconnecting these sources also eliminate the noise?

I ask because I have my MOXF connected via USB to a laptop, and also a ROLAND audio interface connected via USB to the same laptop. Both the MOXF and the ROLAND interface are connected to a mains-power MacKie mixer. And there is high-pitched USB noise on my monitors (which are connected to the MacKie mixer main output bus).

If I disconnect any *one* of the following the noise goes away:

- MOXF USB to laptop
- ROLAND USB to laptop
- ROLAND output to Mixer
- Mains power to laptop

I basically work around the problem by always disconnecting one of the above when working on my productions but it is a pain! All are connected to the same mains power outlet, and it's not a "ground loop" in the traditional sense of the word, as all the RoLAND is bus-powered, and the MOXF and MacKie are powered through SMPS-style power bricks (so no earth).

People have reported success by hacking open the USB cable and splitting the shield with a sharp knife (be careful not to cut into the wires underneath the shield). OR you could try to find an ancient rubbish USB 1.1 cable with no shield at all - if you can find one!

David.