Monitors Buzzing when virus USB connected

[chrisjadescorpion]

hey

loving my virus ti polar. making some nice dnb sounds.
i am getting a horrible buzz in my monitors though. yamaha hs80m's.
my interface is an apogee duet (unbalanced outs maybe?)

i trouble shooted my setup and noticed that the problem starts when the virus ti is connected via usb to my 2011 macbook pro.
when i disconnect the usb - the noise immediately stopped.
possible causes? my first guess would be the virus psu.
my second guess would be the lack of balanced signal from the duet.
this is the email i got from access:

Dear Christopher,
Thank you for your email. This pretty much sounds like a grounding issue with your system. Is this noise on all outputs as soon as USB gets plugged in and are all outs not showing this once USB is unplugged? If that is the case, then it must be a grounding issue with the current setup. Make sure you're using a power conditioner or try changing around your power cabling to see if this makes a difference.

Best wishes,
Jörg Hüttner

ANY HELP WILL BE REPAID WItH SMILEY FACEs.

[Roby31]

It's a grounding issue. Does the noise go away if you let your macbook run on batteries?

[chrisjadescorpion]

Originally Posted by Roby31

It's a grounding issue. Does the noise go away if you let your macbook run on batteries?

when i did the troubleshoot i did the testing with an external monitor.
(i believe a macbook pro will only work with an external monitor if the power cord is connected?? perhaps there is a way around this?)

i will try with just the laptop on batteries and see what happens.
thanks for the tip.

[Timo]

Does the Apogee Duet use its own power supply (to the mains)?

If it can be bus-powered from your laptop/computer, try that instead.

I had a ground-loop problem when I powered my Motu Traveler directly from the mains (while connecting it to the computer via standard firewire). However I built a desktop PC and it happened to have its own powered firewire capability so I completely disconnected the Motu Traveler from the mains and instead used it bus-powered from the PC and the ground loop disappeared. I reckon this was because the PC was fully grounded but the Motu Traveler wasn't (due to the Traveler using a DC power brick/wall-wart without a ground connection being sent to the Traveler, therefore the electrical connection was left 'floating').

Your Macbook pro should also have a bus-powered firewire port too (one of the very few laptops that have them!). As mentioned, also try using your laptop on batteries while powered to the Apogee (itself bus powered if possible).

However, also try connecting any related electrical items to the same mains plug socket (as opposed to using mains plugs all over the room). This way they'll all share the same earth connection. However, make sure you don't overload it! If you use an extender (4-way, etc.), make sure it has a nice thick, earthed 13-Amp cable (or whatever the standard amperage is for Australian electrical sockets). If cables get hot = bad = melting = high fire risk.

After trying all the above, disconnect all audio cables and connect just the Apogee to the speakers. Then the Apogee to the PC. Does it still buzz (without any audio input cables connected to the Apogee)?

Other tips: Try not to run audio cables alongside electrical cables. Electrical cables radiate an alternating Electro-Magnetic Field (EMF), therefore if they happen to run alongside your audio cables your audio cables can pick this ground hum up due to the EMF. If electrical cables have to go near audio cables, try to have them cross each other at 90° as opposed to have them running alongside them.

Use balanced cables where balanced connections are available if possible, this will lessen any EMF interference picked up along the way. Or you could try making up your own psuedo-balanced cables.

Check out these articles on curing earth loops/ground hum:

[How can I stop mains noise in my studio once and for all?]
[Do balanced connections prevent ground loops?]
[How do I get rid of the buzzing noises in my home studio?]
[Audio cables and wiring]

Failing all the above, DI (direct inject) boxes will kill ground loops (albeit on audio inputs only).

[chrisjadescorpion]

thanks timo
that is some awesome advice man.
apogee duet is fw bus powered.
gonna do some more testing on the weekend
and will report back with results.

(i tried the virus ti direct to speakers last night
-no usb-
and there was no buzzing)

hope to get this sorted soon.

[grs]

I found that a Behringer BCD had ground noise with usb to my old laptop.
Weirdest solution was to make a new wire connect from a screw on side of the Behringer to headphone sheild on Behringer.
It's amazing what you can do with a bit of problem solving.

[chrisjadescorpion]

think i finally solved this one.
i believe it was an interface issue, not the virus.
damn apogee duet has unbalanced outputs,
but for some reason the buzzing is solved by using balanced cables!
go figure.
thanks for everyone's help.

[chrisjadescorpion]

man this is so frustrating.
i believe the problem may be with using an external monitor.