JACK + ALSA = NOISY

[Karoliina Salminen]

Hi,

On 9/3/07, Eduardo Pellegrini <haftsnation at gmail.com> wrote:
> I've just installed Ubuntu Studio, and I was playing around with Hydrogen,
> or anything that requires JACK, but everything that plays through JACK
> sounds low, distorted and noisy.

Check if you are getting xrun messages. If yes, your audio buffer is
too short and you
need to increase it and make the latency longer by increasing the
buffers. You can do this
with Qjackctl. Also put RT-mode to on on qjackctl, it helps even with
the standard
non-low-latency kernel. It also depends on which audio hardware you are using.
With C-port the output is not so low, but I can't affect the output
level, no matter what slider I adjust, it is always full. However, I
can set the level on a analog mixer that comes after the C-port before
the amplifier or I can adjust the input that comes to the C-port with
another mixer and I also can of course adjust inside Ardour with the
midi-mixer (Behringer BCF-2000).

>
> Anyway, I've only managed to boot through the regular kernel, the low
> latency one does not boot X (nvidia).
>
> Is this a common problem?

Obviously you don't have the nVidia binary driver compiled against
that kernel, so it will not boot. With my GeForce 8800GTX card, I have
needed to use the nVidia installer with even the stock kernel,
otherwise it does not work. Another thing was that if my memory serves
me right, the Ubuntu was unable to offer correct display mode by
default for my monitor (30 inch Dell, 2560x1600 resolution), so I had
to go to edit the xorg.conf manually and enter the 2560x1600
-resolution there. I haven't dared to try the lowlatency kernel just
yet because it will break the nVidia again.  You need to download the
nvidia installer from here:
http://www.nvidia.com/object/linux_display_ia32_100.14.11.html
Anything that comes with Ubuntu by default breaks miserably, at least
with my GeForce 8800GTX.
With running the nVidia installer, it will start to work. I would like
to advise you to download it before installing the low latency kernel.
Then boot with the low latency kernel and when the X fails to start,
go to command line and run the installer. You'll get X running if you
are lucky.
So you still need to hack a bit to do music with Linux, there is still
a lots of work ahead before it is as easy as on for example Mac that
works out of the box - you plug in your audio interface and it simply
works, you start recording and don't even think about latency and
other weird PC-related issues that make the life of the musician
miserable...

Best Regards,
Karoliina Salminen
(AMD64X2 4200+, GeForce 8800GTX, nVidia nforce motherboard  - running
Ubuntu Studio (Feisty Fawn + some libraries from Gutsy), Ardour 2.05
(from svn), ST-audio C-port DSP-2000 8 channel audio interface + 8
port, 128 channel USB-midi interface + midi mixing console + a stack
of hardware synthesizers, controllers, effects processors, keyboards
etc. stuff. Everything works, including the monitor at 2560x1600
resolution at 24 bits with full hardware accelerated OpenGL, however,
only with the nVidia installer, not out of the box from
Ubuntu-repository).