linuxaudio.org

On Fri, 2010-06-18 at 22:41 +0200, fons@kokkinizita.net wrote:
> The meters are probably completely useless.

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>

> 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

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> 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:

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>

> 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?  I was not sure how to activate K20 or K14 given

jkmeter's interface.

> 2. Set the gain of the soundcard to 0 dB,

Done

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> 3. Adjust the gain of the power amp to the maximum volume

> you'd ever expect for this tyoe of music.

Done

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> 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

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> 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?

Thanks for the help Fons. I appreciate it and your fine software as

always.
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