Minitaur: Digital Noise via USB

[Richard J]

I first tried the Minitaur with a standard 5 pin MIDI cable, and latterly with a USB cable.

I noticed, however, that I get an appreciable amount of digital noise when using the USB cable.

My signal path is as follows:

Miniatur via USB to an iMac i7 (running 10.6.
iMac to MOTU 828 Mk3 (latest drivers) connected via USB (no other USB peripherals connected)
Minitaur audio out to MOTU input using a Van Damme instrument cable.

MOTU, iMac and Minitaur are all on the same power strip (to avoid ground loops).

Any suggestions appreciated.

Richard

[bozechicago]

I am having the same issue. I actually had returned my original unit (due to some strange scratching sound on the VCOs Release/Decay) for a new one, and they both had that issue. I am using an Audio 8 DJ. Everything is in the same strip as well. It very noticeable especially after compressing the signal and giving it makeup gain...

[till]

USB is not isolated for decoupling as the MIDI sockets.
When MIDI was introduced, the makers agreed on using opto-couplers to avoid ground-loops. On USB there is a common ground. So you might try to use one of those expensive USB decouplers. The decoupling might have been build into audio USB equipment by default, but only a very few instrument builders do so.

[bozechicago]

Thanks for the info till. i wasn't familiar with any of that. Already looking into it.
Thanks again dude.

[Richard J]

Until now, I'd never heard of an opto-coupler for a USB cable.

Thanks for the information. I'll check it out.

Richard.

[Amos]

you can cover pin 4 (ground) on one end of the USB cable you're using for the Minitaur and it will avoid this problem.
see this post for more details: http://forum.moogmusic.com/viewtopic.ph ... 07#p114167

this is just one of many ways to resolve a ground-loop problem; they are common in computer music setups with multiple interconnected devices.