USB Playback Messed up

Installation & Configuration Linux
#1

Lets start with specs:
Dual Core AMD Athlon, 2.1 Ghz
64-bit Realtime kernel (2.6.31-10-rt)
Ubuntu 10.04
Jack (or “jackd” as its called in ubuntu) v 0.118.0
NVidia High Definition Audio (internal soundcard)

Jack works great with my NVidia soundcard. But i use an Edirol UA-25 for recording and stuff. Playback using other servers such as PulseAudio, direct connection to ALSA, etc. works great. But no matter what i do, Playback using Jack through my UA-25 card is really messed up. There is this weird distortion. Its like this crunching sound. Jack is running with realtime priority, i have set the limits.conf file as recommended, i joined the audio group, and nothing has worked. I am lost as to what to do. It seems the problem is in Jack as i have managed to play audio smoothly using other sound servers, and yet Jack works perfectly fine on my crappy little internal soundcard. any suggestions?

#2

What are your settings for jack?

#3

Here are my current jack settings. before taking the screenshot, timeout was at 1000, but im going to try 9000.

#4

I have the same card, and works flawlessly, on 10.04. Try to set Timeout (msec) to 9000, and 3 periods/buffers. Frames/period must be no less than 128 for recording, better 256. But if you are mixing something with a lot of tracks and effects, set it even higher to have it reliable.

#5

Does it work? Try seq as MIDI driver, and 3 buffers instead of 4, everything else is ok, it should work that way. Also, make sure the advance mode switch in the Edirol UA-25 is on, and the freq switch is set on 48k.