19 Jun
2010
19 Jun
'10
3:26 a.m.
On 06/19/2010 01:57 AM, Bearcat M. Şandor wrote:
Welcome aboard.
Reducing resolution always reduces the quality - some music just needs
to be played loud! :)
As long as you stay in the digital domain, gain changes will not effect
frequency or phase of the sound. But unless you have pro & high-quality
equipment: the analog part (soundcard, amp, speakers) does in practice
respond differently at different gain levels.
Niles Mayer recently elaborated on that:
http://lists.linuxaudio.org/pipermail/linux-audio-user/2010-June/070249.html
On Fri, 2010-06-18 at 22:41 +0200,
fons(a)kokkinizita.net wrote:
No it does not add up that way. Maybe alsamixer is showing wrong
numbers?! Fons may know more.
The meters are probably completely useless.
The chip used in your soundcard has a digital gain control
with a range of 0...-120 dB in steps of 0.5 dB. Does that
correspond to what alsamixer is showing ? If not you'd
better leave the gain at 0 dB.
Alsamixer reports "dB gain 0.00, 0.00" to -60.00, -60.00 in .5 dB
steps.
Does that correspond to -120 dB somehow (both channels == 120 dB total)?
(i'm a newb at all this) If that
soundcard really has the dynamic range that the
sales blurb claims it has, then its output level will be
a lot higher than what is expected by the average non-pro
amplifier, including 'audiophile' ones.
That means that you should turn down the power amp gain
quite a bit.
This is a low powered 10 watt max amp (class t chip)
The correct alignment procedure would be:
1. Play a piece of music representative of what you
normally listen to. Check the digital level with e.g.
jkmeter, For classic use the K20 mode and ensure you
have a level around 0 dB. For pop use the K14 mode
and again ensure you have around 0 dB.
I compiled and started up jkmeter, then
figured out how to output to it using qjackctl. The alsamixer volume controls make no difference at
all to jkmeter, but adjusting the
volume on mplayer does. Is this the expected behavior?
Yes it is. Alsamixer controls the volume in the mixer of the sound-card.
JACK is all in software. Consider the following (somewhat simplified)
diagram:
JACKified-audio-app
(eg mplayer, ardour, jkmeter)
|
v
JACK-server
|
v
Soundcard ## hardware-mixer controlled by alsamixer
|
v
Amp & Speakers
When you adjust the volume in mplayer, mplayer itself scales the volume.
mplayer does not interact with the soundcard's hardware-mixer. (Well,
you can configure mplayer to do either or both, but the default with
mplayer/JACK is to use mplayer's integrated "amp".)
jkmeter (or any other JACK app) gets mplayer's audio directly from JACKd
without the audio-data going to the soundcard first.
I was not sure how to activate K20 or K14 given
jkmeter's interface.
You need jkmeter version >= 0.4.0.
Run `jkmeter -type k14` to get the K14 scale (k20 is the default)
`jkmeter -h` prints usage and version information.
Information on the K-system can be found in jkmeter's README and at
http://www.digido.com/level-practices-part-2-includes-the-k-system.html
2. Set the
gain of the soundcard to 0 dB,
Done
3. Adjust the gain of the power amp to the
maximum volume
you'd ever expect for this tyoe of music.
Done
4. If you want to avoid an analog gaing control
use a software
gain control (preferred), or the ALSA gain setting as your
volume control.
You mean individual application volume controls as opposed to the
sound
card mixer is preferred?
If the gain setting of the card has any impact on
the magnitude
or phase response then simply the card is out of spec.
If the gain control of the power amp has any impact on the same,
again it's probably out of spec.
As long as you don't overload anything, there should be no difference.
Things like 'fuller bass' are impossible to comment on. If in doubt,
*measure* it.
So even though turning down the apps volume control theoretically
reduces the resolution of the sound it should have no bearing on the
quality of the sound presented? Or do software controls not do that at all?
As long as you stay in the digital domain (here: software) it'll be
"perfect".
Cheers!
robin
Thanks for the help Fons. I appreciate it and your
fine software as
always.