Problems when connecting the USB to my computer

[dmagee92]

Hello everyone,

I've recently plugged my Minibrute into my computer using the USB connection in order to clock the arpeggiator with my DAWs metronome.

When I connect the Minibrute, I can hear a constant hum at a reasonably high frequency which definitely isn't meant to be there. Does anyone else have this issue? Any ideas of how to fix it?

Thanks for all the help,

Daniel

[matias_thinKing]

that's a ground loop issue.  there are many ways to skin the proverbial cat...  galvanic isolation is the ideal solution, albeit not a free one.  if you aren't already, try running all your gear through the same outlet.  I know that may sound like a hazard, but it's highly unlikely you'll exceed 15amps of power, and it will minimize the chances of a ground loop.

another point of interest - we have a pair of yamaha hs80 monitors, and these things are very prone to creating a ground loop problem.  believe it or not, the power cord needs to be plugged in just right on the back of them to ensure proper grounding takes effect...  so sometimes a little jiggling is just what the doctor ordered.

and yet another point of interest - your audio interface and your computer.  usb powered interfaces are prone to pick up ground loops.  we hacked a usb cable to ensure power didn't go through it from the computer.  then we connected it to a little usb cable that comes coupled with a plug for a dc type transformer and used a 5v transformer with it to re-establish power into the usb cable.  finally we connected this to the interface.  it's a hack for sure, but it got rid of the ground loop!

unfortunately, ground loops are a huge pita due to the difficulty pinpointing the culprit in the audio path, but there is light at the end of the tunnel.  hope this helps

[dmagee92]

Im going through a USB powered interface so maybe this is the issue.. Is there any other way to fix it without hacking a cable?

[matias_thinKing]

galvanic isolation + ground lift.  a DI box will do the trick.  for example, the radial engineering JDI.  and with that little guy, you get the benefit of passing your synth's audio through a jensen transformer, which is known to beautify electric audio sources.

be advised, the level (and impedance) of your signal will drop, so you'll need a mic pre to get your signal back up to line level.  a mic pre may already be inside your interface though (as it is with ours - NI AK1)

[dmagee92]

Is there any way you could simplify what you're saying, I'm having trouble following.

Would this ground looping not be an issue if I wasn't using a USB powered interface?

Thanks

[matias_thinKing]

the ground looping issue *may* be resolved if the interface isn't usb powered.  it depends on the implementation of the interface because a usb cable will still carry the +5v and ground, even if it isn't the primary source of power for the device it's connected to.

putting a DI box between your minibrute and your interface is a more likely way of resolving the grounding issue.

I imagine you are using a desktop, but if you have a laptop sitting around, try this:  connect your set up exactly as you normally would except with the laptop as DAW.  now run it on battery (ie unplug the charger).  does the noise go away?

[dmagee92]

Ah I see. Well maybe I should invest in a new interface which isn't USB powered..

I'm not working through a desktop, I'm working through my laptop and I tried disconnecting the power supply but it didn't change anything unfortunately..

I'll look into a DI.

Thanks for all the help. It's much appreciated. I'll be back here if I have anymore issues.

Cheers.

[matias_thinKing]

mmmm ... well hold on a second man.  the noise should go away when you unplug the power supply.  try running the minibrute solo (ie no connection to speakers or USB) and listening out of the headphone jack.  if the noise is present in this case, then contact arturia tech support

[bilbo909]

i have this problem with some other usb based equipment.  this resolved my issues and it's not in the audio signal path so it won't colour the sound.
http://www.electronics-shop.dk/galvanically_usb_isolation.htm?currency=EUR

[dmagee92]

When I took the charger out of my laptop the sound was still there..

When I have the Minibrute running without the USB connection (ie. when I'm not trying to use the DAW's clock) I have no sound problems, the machine sounds clean as possible. It's only when I have it connected up to the laptop that I can hear the high frequencies.

[matias_thinKing]

ok cool - glad to hear the minibrute is in perfect condition.  honestly, I wouldn't have expected the ground loop to remain without AC power going into the laptop, so I'm a little stumped by that.  try one more test.  connect the minibrute to the laptop, have the laptop run on battery power, and do not connect your monitors to the audio interface.  does the noise remain?

with regards to the usb isolator.  we bought one of these in our search for a groundloopfree life too ... look at the description carefully.  all of these things only support up to usb full speed (12mbps), so if your device needs to work at a true usb 2.0 hi speed (400mbps), they won't work.  for an audio interface, it's definitely inadequate, and for midi gear, it may or may not hinder it.  if you want to try this option though, this is a the cheapest isolator I was able to find on the internet http://www.circuitsathome.com/products-page/usb-interfaces ... and the guy was actually super cool and accepted the return of the device once I realized it didn't work with the audio interface due to that full/hi speed issue.

[dmagee92]

I'm not using monitors, my headphones are coming out of my interface. Its just a cheap M-Audio fast track.

I'll try connecting the synth to my computer then putting it through and amplifier although that's probably not the best way to test as the amp probably has a little hiss as well..

[matias_thinKing]

all right ..  I think something may be wrong with the interface or there is some kind of noise being generated by the computer itself (whether by software or hardware).

for a ground loop to exist, you would have to have multiple devices plugged in, and if I understood correctly, you only have the minibrute plugged in.

Is the noise present out of the interface without the minibrute plugged in?

[dmagee92]

My set up is the M-audio Usb interface plugged into one of my laptop's usb slots, then the Minibrute goes into the interface using the usual 1/4" jack, and then the Minibrute is also connected to the second and final Usb slot on my laptop in order to clock it with the DAW (and that's when the noise appears). Both of my Usb slots are used up. Is that enough for Ground Looping?

I've never had problems with noise from the interface so I assume its because of all the Usb slot use, is this right?

[matias_thinKing]

apologies for the confusion.  no, I don't believe it's enough for a ground loop.  when I said multiple devices needed to be plugged in, I meant into a power outlet.  can you record the noise?