[linux-audio-user] M-audio MobilePre USB status

[Alexandre Ratchov]

On Tue, Jan 24, 2006 at 12:40:19AM +0100, Christian Gagneraud wrote:
> Alexandre Ratchov wrote:
> > i'm not a professional, but imo the sound quality is correct. There isn't
> > much noise, i've tried to plug the output of my synthesizer to the input of the
> > sound card and then i've run:
> > 
> > 	arecord -f cd | aplay -f cd
> > 
> > and imo, the result is good;
> > 
> > The mixer works, it's very simple; there are few controls (input gain,
> > output gain, dac gain, and direct monitor gain). The only feature that i
> > couldn't get to work on linux is the "direct monitor" (it controls the
> > amount of the input signal that is routed directly to the output).
> 
> Great, thank you very much for the report!
> This seems quite good.
> 
> Concerning the direct monitor, by default have you some input sound
> routed to output? I mean without playing it back again with a software.
> 

yes, by default, the "direct monitor" feature is turned off; so the input,
is not routed to the output. There is no output until you play any sample.

> > 
> > i don't expect low latency from such USB hardware; i just plan to use it
> > as a simple full-duplex player/recorder. Do you want me to do some other
> > tests?
> 
> Have you some noticable output delay when playing an instrument on input?
> 
> I want to use it to record music from my band. Recording each track
> separatly, while playing other tracks. So i need no audible latency, no
> delay between the moment a note is played on the instrument and this
> note is heared on speakers.
> 

i'm planning to use this sound card for the same purpose (ie playing
multiple tracks while recording a single track). Imho, we don't need
low-latency hardware/software to do this; we only need to synchronize
playback to record and this can be easily achieved with large block sizes
even on a slow machine without preemtive kernel.

(on the other hand, softsynths and real-time effects need fast and
low-latency hardware/software)

i just tried to play a sample (44.1kHz, 16bit, stereo) and to record the
output of the sound card (by wiring its "line-out" to its "line-in"). On a
pentium 200Mhz running openbsd (sorry couldn't get to work my crappy
software on linux) the shift between playback and record is 6ms. this is the
time that the sound takes to propagate 2 meters. While this is enough for
me, i think that the shift will be much smaller on linux, especialy on a
better hardware/software.

> > 
> > 
> >>Do you know if it is an USB1 or USB2 compliant device?
> > 
> > it is USB1.1 compliant; there is no proprietary and/or hidden features,
> > (even the direct monitor is compliant).
> 
> Last thing, what kernel and Alsa version are you using?
> For now, i'm running 2.6.8 with Alsa 1.0.4. I hope i will not have to
> update one of them.
> 

i'm using linux v. 2.8.6 and alsa v. 1.0.4. (debian sarge)

-- 
Alexandre