Well, I've made progressing in playing with Linux for my recording studio. My dad wants to start doing some recording at home and since I've got him on Ubuntu I was going to give him my old M-Audio Duo that I don't use anymore. I was pleased to see that it worked fine out the box with the USB driver and didn't take too long to figure out how to get sound recorded. But as always, the dreaded latency for overdubbing came into play. He wants to lay down track-by-track (I tend to do pure live recording) and that's where things got interesting. By default, it was horrible. The buffer settings required to not get clicks in the recording were way too high to be useful. So I installed the realtime kernel and gave that a try. That helped but it still wasn't good enough. I tried running jackd in realtime mode but couldn't get it started as a regular user, but was successful starting it with sudo, which helped even more. Finally, I found an article online about tweaking the IRQ priority for the USB.
So now I do the following:
sudo jackd -R -P 70 -d alsa -d hw:1 -r 48000 -p 64
to get jack started in realtime mode with a priority of 70 (seems to work fine) using the ALSA drivers and my Duo (hw:1) recording at 48k with a buffer of 64. That gives me a pretty reasonable 1.3ms of latency which is not too noticeable. For some reason I can't set the buffer any lower using the USB device (I also tried my Zoom H4 which also works).
Then I start Ardour with sudo too
sudo ardour2
I think the trick was setting the USB IRQ priority using chrt.
If anyone else is trying to use linux for recording let me know and I'll do a little write up of the steps to help you out.
