Tony
There are a couple of good videos here to get the latency down as low as possible in Reaper.
Either one works. 14/14 is not to shabby I was running with mid 30s until I change my AI recently. And as Lbro described there was a noticeable delay but I followed the first video and got it down to 7/7 or there abouts with a sample rate at 128. I might go to 64 or lower but I was getting some crackling on vox and thought that may be buffer related. Bumped it back to 128 and it was clean again. It was just before the Open Mic so did not want to mess any further.
On the Ai front have to agree with LB if you are going 2 mics 1 Gtr you need at least three separate inputs, which most like means having to go for 4 in 4 out, off course when you come to upgrade.
Cheers
Toby
