Computer Monitor causing 1kHz "whine" noise (not the "brightness" problem)

[theblue1]

I don't have an answer (consider this more a helpful bump back up the page) but, since merely touching the video cable connector to the jack gives you the unwanted noise, it certainly seems to be a ground loop-related contamination of your audio signal with some form of digital signal. (Describing it as saw-tooth-like certainly seems to feed that impression. Digital contamination sounds often have a complex timbre.)

You don't mention an interface. As you may be aware, there have been widespread problems with Firewire based interfaces and signal contamination when used with FW ports controlled by non-Texas Instruments FW controller chips.

(My own ~2003 Dell laptop has such an issue, but only when audio outputs from both my MOTU FW box and the internal interface are both connected to [different inputs] on the same amp. And the noises are intermittent -- but often directly coincident with mouse/screen events.)

Unfortunately, the types and circumstances of such FW-related contamination issues are as hard to pin down as they are widespread.

Hopefully, someone with more direct experience with the particular circumstances you find yourself in will offer some input.

[joedoc]

Thanks so much for the reply. Yeah, I get the feeling that something is feeding into the laptop chassis via the video cable. I set up with just an Mbox2 today, Mac Pro is on the way,, and will be connected then with RME interfaces.

Hopefully that will work alright. If worse comes to worse then I may just go with a PCIe ADAT card, and go optical in. That should cut any connections that are causing a ground loop (if I am properly informed)

More info is welcome regarding the problem or alternate solutions (and experience with them) such as the ADAT i/o option, and if that kicks the ground loop's butt.

[GLouie]

You're using the Macbook Pro's analog output? You have a digital/analog ground loop. This is a fairly common complaint on the Apple forums.

The most effective solution I know of is to isolate the audio output with transformers. In the states, I suggest Jensen for the best, and Radio Shack for those that don't care too much. It can be argued that Radio Shack is fine if you are using the built-in Apple analog output instead of a digital interface. I do not know what is available in Germany.

Ground Loop Isolator - RadioShack.com
JENSEN TRANSFORMERS, INC. - ISO-MAX® Audio Isolator Products
Ground Loop Isolator : Multimedia Accessories : Maplin

[valis]

What interface are you using for your audio? Firewire interfaces that run on their own power seem to like having the bus-power supplied by the Macbook Pro's 'broken' (convert to 4 pin & back to 6 pin for firewire400 for example.)

I would wonder if you have a floating ground too, are you using the 3 pin cable supplied with your Macbook's transformer?

[joedoc]

Thanks cats! This is getting me onto the right path.

Originally Posted by valis

Firewire interfaces that run on their own power seem to like having the bus-power supplied by the Macbook Pro's 'broken' (convert to 4 pin & back to 6 pin for firewire400 for example.)

In this case I was using an Mbox2 (USB connection). I assume you mean that the bus power could be broken, and then switch to using an external supply... For the Mbox that unfortunately isn't an option. However, I'm switching over soon to an RME Fireface setup, and then this would be an option.

How do I do this? Is it as simple as playing Dr. Frankenstein with a Firewire cable & soldering iron? That I can handle!

Originally Posted by valis

I would wonder if you have a floating ground too, are you using the 3 pin cable supplied with your Macbook's transformer?

THIS may be it. I've been using the Macbook's power Xfmr with a US-Europe adapter, and the ground is lifted. So if I cut into the 3-prong extension cable, and wire on a Euro 3-prong, it will be grounded.

Do you think that will stop the whining (not my whining, but the monitor's)
- if this path to ground is available?

Thanks so much again, guys.

joe

[joedoc]

So, I fired up the soldering iron, and attached a European 3 pin (grounded) power cable to the power transformer for the macbook pro.

Still getting the "whine"...

So that wasn't it.

Does that mean that if a bus-powered usb audio interface is attached, that there's no way to get rid of the noise?

[valis]

No, I get issues when I use a device that *can* be bus-powered but is instead running off a separate supply. Meaning that I find 'breaking' the power supplied by the bus (by routing through a converter or something that removes power from the pins) resolves this. However since you're using USB that's a separate (though possibly related) issue as a firewire 4 pin connector won't help

[Mavro]

I got the same problem with my mbox 2 mini and i cant figure out what the problem is. Everytime i start somthing that handle sound on my computer or when a sound is generated the 1kHz whine noise appears. But the sound is gone when my computer is turned off or if its just turned on without any program or such up.

I cant figure out what it is. I have connected all AC power conections to the same connection. And i have moved around cables and the mbox 2 mini to see if the sound disapeares, but it wont go away. I have tried with only the mbox 2 mini and my mouse connected in all usb ports. But the sound is still there.

Did you solve the problem ?

Btw i use a PC and balanced xlr (hs50m) -> 1/4" tele (mbox). I think the output of the mbox is unbalanced but less of the whine 1 kHz noise is generated when i use balanced instead.

[Mavro]

Okey this is realy strange but i think i solved the problem.
What i did was moving my computer away from the right side of my table to a place between my speakers under my desk. And i changed so the speakers AC power cables was connected to a own wall socket and that the computer was connected with all its power cables to a own wall socket.

Another thing i did was inserting the usb cables a bit different. Anyway now its gone but i dont know what i did to make it go away ^^. Whats do you guys think fixed the problem?

Im going to make some more investigation and try to find out what was the problem.

[Schmenge]

FWIW regarding the MBox 2 Mini, I had the same problem, and found peace (well, at least on this front) by following the DUC recommendation and getting a Monster "Ultimate" shielded USB cable. They're pretty spendy, but if you look hard you can get 'em for a little less than half price. This solution really works, and seems to be the only way to silence squealing MBoxes. I wouldn't go this route if there were *any* other solution. As a Seattle native, and general hater of all things creepy, I am sickened by the stunt Monster pulled on Blue Jeans Cable (look it up). I won't allow any other Monster products in my house, save for this one, which I hide behind my desk...

[rksguit]

Originally Posted by joedoc

Mac Pro is on the way,, and will be connected then with RME interfaces.

Oh to have money.......I can sort of remember what that was like[?]

[RiF]

It's a well documented bug on the Mbox Mini (mine has it too, google foe "mbox whine"). I tried several different usb cables and what not, but to no avail. Btw, it should go away when you unplug the power cord and run on batteries.
Dump the mbox and get any other interface.

[PaPi61]

Here's the solution:

[valis]

Originally Posted by PaPi61

Here's the solution:

I have a few of these, only breaking FireWire power worked for me...

[rksguit]

Originally Posted by Schmenge

I am sickened by the stunt Monster pulled on Blue Jeans Cable (look it up). I won't allow any other Monster products in my house, save for this one, which I hide behind my desk...

This is copied,from another forum,in reg. to Montster/HDMI.......
"I wont lie, i use a Monster 700HD Series HDMI Cable which cost me $280, but these new 1000HD series cables are $410 for a 1.5m Cable..."

[Timur Born]

Blame the manufacturer of your laptop who doesn't know how to properly implement grounding (try measuring the mass of your Mac vs. earth under different load conditions and wonder what Apple defines as 0 volts).