Re: [LAU] M-Audio fast track pro mic input fails with smaller buffer size

On Sat, Oct 27, 2012 at 04:18:43PM +0800, James Harkins wrote:
> Has anyone else had this problem? For some pieces using live mic
> input, I wanted to reduce latency by pulling the Jack IO buffer size
> down to 512 samples from the default 1024. (I also tried 256
> samples, but that just made Jack crash.)
>
> But with the smaller buffer, the mic gets an additional 30-40 dB of
> gain, making the input unusable. If I turn the preamp on the fast
> track down very very low and speak quietly into the mic, the sound
> comes through without obvious distortion or glitches, so it doesn't
> seem to be an xrun thing. But it distorts very easily and very
> badly.
>
> If I switch back to 1024 samples, the problem disappears.
>
> Why would the driver's buffer size have an impact on the incoming
> signal's gain?
>
> Thanks,
> hjh

Hi James,

I've too have an M-Audio Fast Track Pro and I've found that it's audio
capture works unreliably under Linux. I only tested it using arecord
and I have not tried Jack.

I find that on random takes the audio will become heavily distorted.
Usually this sounds as though additional gain is being introduced and
there is what sounds like very audible quantization distortion. Once
the problem appears, it persists until the device is reset.

If you are able to successfully configure this device for recording in
any capacity you are doing better than me. I have found the device to
be unusable for capture which is a shame because it's the only device
I own. I'd be interested in testing your configuration on my own
device. I would love to get this thing working.

There don't seem to be many Fast Track Pro users out there; in fact,
you're the only other person I've heard from thus far.

-- Lewis
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Received on Mon Oct 29 20:15:03 2012