[linux-audio-user] noisy capture->playback

Jan Depner eviltwin69 at cableone.net
Sun Nov 2 10:48:44 EST 2003

I'm not sure I'm following this.  How have you got envy24control set
up?  Are H/W Out 1/2 set to PCM Out 1/2 or Digital Mix L/R?  I've had a
problem that sounds similar when using the Digital Mix L/R combo.  I
found that muting all of the channels except PCM Out 1/2 cleared it up. 
I think it was that PCM Out 1/2 were being overdriven.


On Sun, 2003-11-02 at 09:20, David wrote:
> Hello all !
> What could I do about the following problem ?
> I have an M-audio delta66 + omni I/O (preamp/breakout box). This card
> has an onboard digital mixer that allows hardware monitoring of inputs.
> - when setting this mixer to directly route a HW input to a PCM output,
> the sound is perfectly fine. The signal goes through both an A/D and a
> D/A conversion before reaching my ears. I suppose that if I had a ground
> loop problem (or other analog noise source), I would hear it with such a
> setup. 
> - now, when using jackd to route (with no jack client in between) the
> alsa capture port associated with the HW input to a playback port, the
> sound is full of horrible "blips".
> I use :
> - IRQ #10 for the delta66 (I even disabled the USB controller of the
>   motherboard which used IRQ#11, with no better results).
> - a patched for LL 2.4.19 kernel, ext2 filesystems and hdparm'ed HDs.
> - alsa 0.9.6
> - a tmpfs work directory for jackd that I start with '-R' as root.
> How could I isolate the source of this very annoying problem ?
> Is there a way to route an input to an output through ALSA only without
> using jackd (and the hw mixer too of course) ? Maybe that would help
> tracking down the culprit ...
> I'd appreciate any hint on this. Thanks a lot !
> --
> David

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