USB Squeal when using an extra vid monitor

[Deirdre B]

Hey Gang! Happy New Year!

I've got a little home studio where I do my voice over stuff.
Most of the time, I've recorded thru my G4 laptop to an external FW HDD.
My new mic is picking up the whir of the laptop's drive, so I moved it onto my rack and got a flat screen monitor which is set to mirror.

Now I've got USB squeal when I monitor playback. It's not feedback. It's apparently not infecting the record side of things unless I'm recording something from my computer's audio out port, plugged into my Mackie Mixer. It's only when the video out from the Mac is active.

I've tried a new USB cable, a USB different port, different dongle for the video out, plugging the Mackie's power cable into another circuit in the house. Forget it— as soon as Digi Core Audio is engaged, there's the squeal.
I'm waiting on a DVI-DVI monitor cable. I don't know if it will have an effect, but it will be interesting to see.

The fews threads I've found here about this issue don't seem to be resolved. I can't be the only one with this trouble.

[Deirdre B]

I've looked all over the net for the cause, and the general consensus seems to liken the whine to a 60-cycle ground hum— like it's the digital equivalent of a ground loop. The damnable thing is that it seems to be "looping" thru the chassis or body of my computer, so there's very little recourse. I've got the best cables money can buy, and I've even put adhesive tape around the video port to keep the metal sleeve of the video cable from touching the aluminum body of the computer.

It's still there. It drives me bonkers. I only hear it on playback, but it pollutes the process.

[DigiTechSupt]

Have you tried the suggestions in the General Troubleshooting thread regarding this particular problem?

[Deirdre B]

Dear Digi Support,

Yes, I had done a great deal of this stuff, and have also had the additional frustration of not being able to use the headphone output from my Mbox 1 because the right channel isn't playing back thru either jack, the 1/8' in the front or 1/4" in the back.

I've been using the rear outputs from the Mbox1 to channels on my Mackie to monitor playback which was fine when I was just using the Laptop's screen. The introduction of the extra LCD monitor made the noise show up.

The ONE THING I hadn't tried was a balanced cables OUT of the Mbox1 to balanced channels on the Mackie. Mega w00ty goodness! The playback whine is gone.

Many Many Thanks!

[Deirdre B]

The PLAYBACK whine is gone, so now I can clearly hear the whine that's being recorded. Freakin' meh.

I have tried using different circuits for all my audio stuff, the same circuit for all my audio stuff.
It's absent when I just use the laptop, and is present only when I engage the video card by plugging in an external monitor. And it's an LCD monitor, not a CRT.

For what it's worth I have tried:
using a power conditioner for all my electronic gear: Monster.
unplugging the power supply and running off of batteries to see if noise goes away. (It didn't)
Unplugging all unnecessary gear and running only the computer, the mixer and the Mbox 1.
Listening through headphones.
Making sure I used a USB cable plugged directly into the computer.
All USB ports on the computer to see if the noise lessens.
Tracing my cable path for long cable runs, and isolating my cables from possible interference.

I can't recall if I've tried bypassing the mixer for the mic yet, so I'm not sure what the result of that will be, but I have taken the channel strip out of the equation. Just recording the Mbox 1 plugged into the Mac will be interesting to try. Also on the docket are lifting the mixer off the ground, lifting the computer off the ground, a Monster USB cable, ferrite chokes, and abandoning the whole godforsaken thing and trying to fabricate a case for my laptop that will obliterate the sound of the whirring hard disk drive without obscuring the screen.

[Deirdre B]

Today I got rid of the 2Khz whine in my audio chain.

All I needed to do was "lift" the power plug for the LCD monitor. I just used one of those three-to-two prong adapters and poof!

No More Noise.

It's a great day for America!