Computer noise carrying through USB Cable

sproyd · Post by **sproyd** » Fri Jan 21, 2011 8:52 pm

I've now found that even with the microStation off and with the USB not plugged in I get a very very quiet high pitch noise coming through the MBox outputs. I know its from the mS because when I unplug the line outs from the mS the sounds goes. Once I plug in the USB (with mS still off) the noise amplifies to the usual static high pitch hiss coming through the USB cable.

The noise doesn't actually change much once the mS is turned on.

Yes the mS was purchased in NZ and using the provided Korg branded AC plug. Now the noise continues even with the AC completely unplugged!! Does this change anything?

synthjoe · Post by **synthjoe** » Sat Jan 22, 2011 12:13 am

Typical ground loop problem, I'd say. Try the cable I suggested or a DI box - the the former is a bit less likely (though cheaper) but the latter is very likely to solve your problem.

The faint noise you hear when the mS PSU and USB are unplugged is likely down to the quality and positioning of the audio cable(s) you use (do I understand you correctly that you get this when both USB and PSU are disconnected from the mS?). It's just a guess worth considering, not to offend your gear - but probably not the most severe of all the deficiencies adding up to your final problem here.

sproyd · Post by **sproyd** » Sat Jan 22, 2011 3:17 am

Ok cool - and where would I get a cable like this? Do you have a link? Sorry I'm not great with electronics

xmlguy · Post by **xmlguy** » Sat Jan 22, 2011 5:27 am

You can try unplugging your MBOX entirely, then hook the microStation audio outputs to the regular audio input on the computer.

sproyd · Post by **sproyd** » Sat Jan 22, 2011 6:40 am

I dont think there is much point having the audio out of the mS to the computer as the recording quality will be terrible.

On that point I made a quick beat entirely out of mS sounds through MIDI on PTLE and recorded it through the MBox2.

DISASTER. All the lows sound like turd and you can hear the whine. There is no clipping here, the sound is fully dynamic just horribly distorted. Look forward to comments!

http://rapidshare.com/files/443883159/123.R.mp3

The thing is though there was no distortion coming through the system until I started recording??

xmlguy · Post by **xmlguy** » Sat Jan 22, 2011 12:17 pm

sproyd wrote:I dont think there is much point having the audio out of the mS to the computer as the recording quality will be terrible.

How do you know that, until you try it?

There are many reasons to test it. If you get a clean recording using the regular aux in, then you'll know the MBOX is at fault.

By the way, the recording quality is usually pretty good on the standard computer aux/line in. The reason we normally use a sound card is to get low latency and more features. I've frequently recorded from a computer's audio in and got excellent sound quality, depending on the motherboard. I don't make my suggestions frivolously, and there's many good reasons behind my suggestions. There's a method behind my madness, trust me. If I had the system in front of my on my workbench, I could probably find the problem and fix in in less than 5 minutes. When having to post through a forum, it takes much longer, so please be patient.

synthjoe · Post by **synthjoe** » Sat Jan 22, 2011 1:44 pm

sproyd wrote:I dont think there is much point having the audio out of the mS to the computer as the recording quality will be terrible.

On that point I made a quick beat entirely out of mS sounds through MIDI on PTLE and recorded it through the MBox2.

DISASTER. All the lows sound like turd and you can hear the whine. There is no clipping here, the sound is fully dynamic just horribly distorted. Look forward to comments!

http://rapidshare.com/files/443883159/123.R.mp3

The thing is though there was no distortion coming through the system until I started recording??

My guess is that it comes from the buffer sync problem Mbox/ProTools sometimes has. Reload the DAE engine or reboot ProTools while disconnecting/reconnecting Mbox, it should solve your problem.

Alternatively, try to increase the buffer size setting to the next greater value in the 'Setup/playback engine' menu of ProTools.

synthjoe · Post by **synthjoe** » Sat Jan 22, 2011 1:57 pm

sproyd wrote:Ok cool - and where would I get a cable like this? Do you have a link? Sorry I'm not great with electronics

Sorry, in that case it might be a bit more difficult. Either you have to buy it as a special cable in a decent audio/pro music store (not cheap, probably in the order of US$10-20 apiece), or get someone to make it for you (a knowledgeable friend might be able to do it for you in 30 minutes or less).

It is really not a big deal, but if you don't feel comfortable doing it yourself then you'll have to pay for somebody's time, and that's not going to be cheap. Alternatively, at that same price you might even get a useable DI box - be sure to check it out first.

synthjoe · Post by **synthjoe** » Sat Jan 22, 2011 2:36 pm

A couple of solutions you might want to check. I'm not endorsing them in any way and have not tried these products, so I cannot comment on their quality, you'll have to check for yourself.

http://www.behringer.com/EN/Products/HD400.aspx
http://www.artproaudio.com/products.asp ... t=15&id=60
http://www.csbmusic.com/index.php?productID=3
http://www.palmer-germany.com/38-1-pan04-passive.html

...and many more.

Edit: watch out for the Palmer and Art poducts above, they have XLR output, rather than 1/4" (6.35 mm) jack - I guess that would not be practical for you. But Mbox can accept that, as well, if you have two XLR/XLR cables to connect the DI box with it.

sproyd · Post by **sproyd** » Sat Jan 22, 2011 8:29 pm

The Behringer looks best and is well priced at c. USD30 but... I'm in NZ and the rip-off merchants here have a retail of NZD89 which translates to USD68... ha

I may just bite the bullet

sproyd · Post by **sproyd** » Sun Jan 23, 2011 4:58 am

Okay I use Sweetwater a lot.

Will any of the following do the trick and which one would you recommend?
http://www.sweetwater.com/store/detail/SDirectPlus/
http://www.sweetwater.com/store/detail/ZdirectDual/
http://www.sweetwater.com/store/detail/CleanBoxII/

Or anything else on this page
http://www.sweetwater.com/c957--Direct_Boxes/low2high

Also what are good cable recommendations for synth to DI Box and DI Box to MBox2?

Cheers

synthjoe · Post by **synthjoe** » Sun Jan 23, 2011 10:09 am

I would not recommend the Samson for three reasons: 1. there's nowhere a mention of transformers, which worries me as to perfect isolation (Behringer DI-20 is cheap but it has no transformers, either), 2. it is an active box, meaning that you have to use a battery or XLR cables for the Mbox to power via phantom power (and hence will not work with inputs that cannot provide phantom power), 3. has only XLR outputs which is not really convenient in an environment like yours.

ART Zdirect Dual looks pretty much like the one you want. CleanBoxII has no mention of transformers either, but since it is a passive design and would be difficult (if not impossible) to do an electronic isolation in such a design, probably does what you need.

As for the cables, I'm not a big fan of fighting which copper conducts electricity better, so I'd say as long as they're decent, probably you shouldn't worry. Maybe someone else here will chime in with better advices on cable.

A final word of warning: listening to the recording you posted the noise level does not seem that terribly high to me, which means that it _might_ be something else. I still think it is a ground loop problem, but would not like to push you to spend another 50-100 bucks just to fail. So I suggest try to get a DI box from a friend to test, they are common in sound reinforcement and studios, I'm sure you have someone who can lend you one for a few hours. Just to be on the safe side.

sproyd · Post by **sproyd** » Mon Jan 24, 2011 9:19 am

ZDirectDual and a bunch of cable are on their way from Sweetwater USA as we speak...

crofter · Post by **crofter** » Sat Jan 29, 2011 1:39 pm

I get the same noise from my Blofeld when the usb cable is plugged in, one of these between the Blofeld outs and the mixer sorted it out,
http://www.maplin.co.uk/ground-loop-isolator-33172

sproyd · Post by **sproyd** » Wed Feb 02, 2011 2:42 am

Everybody, I have GREAT news.

The problem has been 100% fixed. And I think the microSTATION is now sounding even better than before!

I have run my 1/4" unbalanced outputs from the microSTATION into an ARTcessories DualZDirect ( http://www.sweetwater.com/store/detail/ZdirectDual ) and then I am running the Balanced XLR outputs into the 1/4" balanced inputs on the MBox 2. There is a switch on the back of the DualZDirect for each of the ouputs that is a ground lift. When this is depressed, and only when, the noise disappears, therefore confirming the hypothesis that this is a ground loop program.

Thanks to all involved for your help. Had to swallow a bit of $$$ to get it fixed but I'm not sitting pretty! To recap I have bought
- A new low-noise high Wattage power supply for my PC
- New Roland MIDI Cables
- ARTessories DualZDirect
- a pack of unbalanced 1/4" cables
- Proel Italian Neutrik XLR F to 1/4" balanced