I have a Yamaha mixing board, recently aquired, and a Graphite iMac. The headphone out crackles when I wish to use it as an audio return. And the iMic hummmms. I have connected them to the same power source (AC outlet) and still the same problem. If the iMic or headphone out is lead to a pair of Headphones, the humming and or crackling does not exist. Is this my computer, or my mixer?

iMic is plugged into one of the two USB slots, not hub. I am looking at an Edirol USB capture. But other postings indicated that it's USB related and won't be solved by a different device.

I have a Firewire DAZZLE video bridge, but I don't think that can be used as an audio capture. Any help is welcome.

Mixolidean

If it'd be the computer you would have it on the headphones… so the origin must be either in the interface or in some ground loop.

For the iMic it's a bit noisy, there's a third party driver (for $) which does marvels and brings the best out of it, it's still an entry level interface but then with a proper driver. Search USB-ASIO int eh soft/drivers section.

Before that you can switch it to the other USB port and control the Audio set up in the system is on 16 bits (found that on XLR8yourmac).

If it's a ground loop the only way to get rid of it is to cut it in some way : use a cable with the earth lifted at one end of it.

Hope this helps…

I don't know the Dazzle thingy so I can't tell you.

Oops… one thing can explain the crackles too: bad buffer set up if you are using an app with one that has some possibilities of fine tuning it : if so, set the buffer higher until the crackling disapear.