MBOX High Pitch Noise. Pls HELP

[Alexis CC]

Hi there

When I connect my Mbox to my Stereo speakers (yes, stereo speakers, not studio monitors), it produces a very loud and annoying high pitch noise. The funny thing is that if I connect the Mbox to my DAT machine via SPDIF, and then connect the DAT to the stereo it won't happen.
I am connecting with a stereo 1/4 inch to stereo RCA cable. Mbox TRS line out to the stereo In.

I know other people that have an Mbox and they connect it to their stereo through the headphone utput! and they get no hum.

I called DIGI a while ago (while still in warranty), and after waiting for 45 minutes their answer was that the Mbox is NOT supposed to be connected to a Stereo. They said that even though it's a home oriented product it requires Professional studio monitors (can you believe that??). Not only they didn't provide a solution, but they were very snobby about it. I found it obnoxious and frustrating.

I am pretty sure that there is a grounding problem, and that it's easy to solve.
My problem is that I know knothing about grounding... I know it sounds stupid but thats's what it is!

Any help will be greatly appreciated. Maybe Digi wants to face the problem this time??

Thanks

[DigiTechSupt]

Hello,

First make sure you have Service Pack 1 installed for XP. Not having SP1 can cause whine problems. Also, check the following:


-Since most third party USB cables do not include a bulk filter (the cylindrical lump near one end of the cable) to help reduce interference, make sure that you are using the USB cable that ships with MBox.

-I would also make sure you are running the updated firmware. Go to: Program Files > Digidesign > Pro Tools > Pro Tools Utilities and run the firmware updater. After that try uninstalling and reinstalling ProTools software and hardware.

-Trash the following items from the system and restart the computer:
-DAE prefs folder: Located in the C:/ Program files / Digidesign / DAE folder
-PT prefs file: Located in the C:/ Windows/ Application Data/ Digidesign folder.

-Try using another USB port on your computer.

-Try removing other USB deivecs from the system as a test.

Mike

[O.G. Killa]

to fix the grounding you may have to solder the cable yourself.

in a TRS connection the Tip is hot (or called Positive, or +), the Ring is cold (or negitive or -) and the sleeve is the ground.

There are two ways to wire an unbalanced signal to a balanced signal.

a) Connect the Tip of the 1/4" TRS to the Tip of the RCA connector, Then connect both the ring and the ground to the outer ring of the RCA connector

b) Connect the tip to the tip, connect the ground to the ring, but leave the ring of the 1/4"TRS unconnected to the RCA plug. In essence leaving the cold (or -) lead unconnected.

I would usually recommend choice A. But I noticed on the back of one of my 192s it says, "NOTE: Leave negative terminals unconnected when driving unbalanced loads" which would be choice B. If you have to do this for the 192 I/O, maybe you need to do it with the MBox as well? *shrug*

If you haven't already, I would recommend just going to the store and buying a pre-made balanced 1/4" TRS to unbalanced RCA cable. Maybe go to a music store instead of Radio shack to get one in hopes that the negative lead is unconnected. But, if your feeling adventurous you can try to make one yourself.

[Stone Knife]

Bring home flowers. That can abate some of the high-pitched whining. [img]images/icons/wink.gif[/img]

[groovilator]

I also have an MBox which I monitor through my stereo and high pitched whining has plagued me as well. What I noticed though is that when I would listen to any other audio from my computer (MP3's, streaming audio, whatever) I didn't get the whining. So I tried unplugging the RCA's that come in from the output on my computer when I would open Pro Tools and that has solved the problem for me. If the back of your stereo is easily accessible then perhaps you'll find it's not that big of a hassle.