noise with USB attached

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noise with USB attached

By arebee Fri Nov 21, 2008 4:55 pm
i sometimes get a high frequency band noise whenever my USB is attached to the MPC. depending on the setup - ie:where i have my MPC placed in the studio. disconnect it and the noise is gone, its something to do with the power down the USB line i think, anyone also notice extra noise with USB plugged.

Re: noise with USB attached

By Forax Sat Nov 22, 2008 12:29 am
yeah I have the same thing too.. have to remember to unplug it when doing recording

Re: noise with USB attached

By jackymurda Sat Nov 22, 2008 6:50 am
think it might have to do with rfi on the ground connection between the usb host and the mpc..since the mpc's output amplifier's are unbalanced, its probably better to just unplug the usb than get into arcane grounding schemes...
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Re: noise with USB attached

By Sooty_G Sat Nov 22, 2008 10:47 am
arebee, let me ask you this: are you also using a firewire audio interface when you get the noise? and can you also 'play' the interference noise by performing actions on your computer (like moving the mouse and opening / closing windows, apps, etc.)?

i have got this same problem with only 2 other pieces of gear: a clavia nord mod g1 & a nord mod g2. :( it has something to do with a loop created when you have the gear connected via usb & a firewire audio interface simultaneously. the mpc will get the noise to a lesser degree but it isn't as much a problem since i don't usually keep it connected via usb all the time. it is much more a problem with the nords since you generally want to keep them connected so you can use the editor.

funny enough, i also have an evolver synth but it does NOT have this problem. ???

research on the nord forums has indicated that some people have solved the problem by ground lifting their power cables with a 3 to 2 prong adaptor but this hasn't worked for me. i'm running a laptop and even if i unplug the laptop and run on battery power i still get the noise ( tho it does get reduced a bit ). another solution mentioned was to physically alter a usb cable (cutting the wire that carries the power) but i'm scared to do that for fear of damaging my computer when it's plugged in.

if anyone manages to solve this problem please let me know because it is driving me insane with my nord !

Re: noise with USB attached

By jackymurda Sun Nov 23, 2008 6:22 am
^^^^^^

yup.

there is a ground loop . with unbalanced connections getting rid of it can be hard, as the current flowing through the usb is modulating the 0V ground level at 60/50 Hz..
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Re: noise with USB attached

By arebee Mon Nov 24, 2008 1:51 pm
Sooty_G wrote:arebee, let me ask you this: are you also using a firewire audio interface when you get the noise? and can you also 'play' the interference noise by performing actions on your computer (like moving the mouse and opening / closing windows, apps, etc.)?

yup - well, nope, i have a belkin USB hub, to enable enough power to USB devices - i use the FW connection too - FW helps to 'power up' the hub's USB ports, so any hungry USB device doesnt fail me when im using bus power only.

it still occurs when i unplug MPCs audio cables (in/out), so its really all about the usb, and then if i unplug the FW (mac host) cable feeding power to the hub, it kills the noise . so its defo power related, and yes depending on the drain / ie: the amount of devices attached to the hub - its makes different noise tones.


...."( it has something to do with a loop created when you have the gear connected via usb & a firewire audio interface simultaneously"

true for me too


research on the nord forums has indicated that some people have solved the problem by ground lifting their power cables with a 3 to 2 prong adaptor but this hasn't worked for me. i'm running a laptop and even if i unplug the laptop and run on battery power i still get the noise ( tho it does get reduced a bit ). another solution mentioned was to physically alter a usb cable (cutting the wire that carries the power) but i'm scared to do that for fear of damaging my computer when it's plugged in.

- well heres the deal - im using those blinging led cables - yknow - the ones with pretty lights at each end, i thought i could be that.

but really its all because i prefer the idea of BUS POWER!, so as a result using the FW to feed it, and thus the 'simult FW/USB concerto'

pce.
not a big deal - cos i dont really use the USB much on my MPC cos its sooooo slow, i often use my PCMCIA/CF adapter in my powerbook G4 for faster transfers anyway.....unless im hosting to my G5 desky.


if anyone manages to solve this problem please let me know because it is driving me insane with my nord !
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