Forgery League: The Lab

Wednesday 7 March 2007

Mbox2 addendum

I thought I’d peek at my server statistics for Forgery League, and see how people found their way to the site. One person apparently Googled “mbox high pitched buzz”, so I figure it’s a good time to mention:

I figured out what was causing the quiet whining noise on the Mbox’s monitor outputs. It was happening every time there was audio, which gave the impression that it was the data stream coming in through its own USB port. However, it turns out it was actually the video output. I’d attached a monitor to my PowerBook (an “Aluminum” series G4 with DVI video connection), and when I disconnected it, away went the screech.

Strange: the signal to the Mbox is digital, so you’d think it wouldn’t be susceptible to interference. Does the monitor signal introduce so much noise that it can travel down a USB cable and get picked up by the analog circuitry in the Mbox?

Sadly, this means having to use Logic on one small laptop screen some of the time, but I’m certainly glad I don’t have to get another outboard audio interface.

I haven’t yet tested whether it only appears on the monitor outs, or whether it gets recorded too, and whether it helps to use a different/better USB cable. I’ll do some more playing around when I get a chance. Stay tuned.