Ground loop type noise/hum using KP3+ USB connection...

[Mr36]

Been a very long time since I was last here and posting... Hope all are well.

Hopefully someone can shed some light on this and not conclude that it's either not possible to get round it and/or it's an inherent problem with Kaoss Pads...


I have my master output from my laptop running into the KP3+, which is also connected via USB to the laptop.
However, this results in a very audible "ground loop" type hum/noise and the only way I have found to get rid of it is to disconnect the USB cable from the KP3+. Is this expected behaviour? Surely not... Though I realise a kind of loop is being created (laptop > KP3+ > laptop), but surely this shouldn't present a problem when the KP3+ and soundcard are on different buses...

I am using an Alienware M14x laptop (i7-2720QM, 6GB RAM, SSD boot disk) with a Native Instruments Komplete Audio 6 audio interface (connected via USB), which feeds the KP3+ via RCA cables.

I have tried different cables and even the mic input instead of the RCA to no avail.

Thanks in advance!

[bradkorg]

See thread: http://www.korgforums.com/forum/phpBB2/ ... 381a7913a5

Now your mS USB [ground]-PC connection is causing the Ground Loop noise! because the audio ground is also connected to PC.
Double grounds to PC makes the groundloop statics noise!

Just test it without USB conneected, you will get clean sound from mS line-out to PC soundcard line-in directly!

-Simple solution fix: just cut the USB cable ground pin 4 and/or shielding.
-I bought a cheap 4 ports USB hub from ebay and cut inside the ground trace/shield to the usb output port(s).
Remember now mS USB will be only active when the audio line is connected to PC also, because USB ground will now using the only one audio ground.
I get the same clean sound likewise as without USB connected, just perfect sounds!

Ref:
http://www.archonmagnus.com/computing/elec/USBpins.php

http://www.moddiy.com/pages/USB-2.0-%7B ... nouts.html

http://www.head-fi.org/t/686609/usb-cab ... dac-solved

http://www.theworshipguitarist.com/blog ... liminated/

Cut the ground from the USB to KP3 ONLY.
Common usb/audio groundloop problem with pc/laptop, because they shared the common grounds.
Maybe higher-end separated int/ext soundcards have separated audio-ground.

-Make sure it has only 1 (audio) ground connected between them, if you also use the KP3 Audio OUT into PC Soundcard Audio IN.
This add the 2nd ground, so groundloop noise could return, than one of the audio groundwire to pc need be cut.

[Mr36]

Thank you very much for the prompt and detailed response. Not sure how/why I didn't see that thread in my searches, but thanks.
(Probably because I searched Google generally and the Kaoss forums here specifically.)


However, that seems to be about audio going into the laptop from the other device. Is this applicable to audio from the laptop (via USB soundcard) to the other device too?
If so, that's a big shame I'd have to make cable modifications to be able to use the devices in this way.

Thanks again for your help.

[bradkorg]

Mostly it doesn't matter if it's Analog Audio IN/OUT to PC, as long as USB grounding/shielding is involved.

Best is to try it out if groundloop/PC noise is too much or not.
Only if you're using Optical Audio/SPDIF IN/OUT connections, than it will be groundloop free without any modifications.

[Mr36]

Thanks for the clarification.