From alsa-user-owner@alsa.jcu.cz  Sat Dec 19 10:31:04 1998
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	Sat, 19 Dec 1998 10:27:45 +0100
Date: Sat, 19 Dec 1998 10:27:45 +0100 (CET)
From: Jaroslav Kysela <perex@jcu.cz>
To: Kerry Hoath <kerry@gotss.ml.org>
cc: alsa-user@alsa.jcu.cz, alsa-devel@alsa.jcu.cz
Subject: Re: Microphone gain on GusMAX
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On Sat, 19 Dec 1998, Kerry Hoath wrote:

> Ok this was more apropriate for the alsa-user list so I repost it here now.
> Sorry for not reading the mailing list names mor clearly.
> 
> Hi, I am not subscribed to this list but intend to subscribe very soon. I
> am having trou	have a general question regarding the GUS max soundcard and
> ALSA driver 0.2.0p10.2.
> 
> When I attempt to sample with this card, from the microphone, the levels
> are far too high and the sound clips. I tinkered with the Mic levels, with no
> success. I then looked at /proc/asound/card1/mixer0 but found nothing relivant
> there.
> Out of curiosity I looked in /etc/asound.conf and found an undocumented
> "MIC Gain" setting set to true. I Changed it to "false" and my Microphone
> works properly.
> 
> My questions:
> 1: Is this documented somewhere, if so where?

In alsactl man page (which is probably only on CVS).

> 2: Would you like help with the docs? I'm no programmer but the current set
> are horrific in my opinion <smile>.

John Fulmer <jfulmer@appin.ml.org> is working on ALSA Users Guide. Maybe
he requires some help. I'm waiting for this Users Guide and for corrected
ALSA API document for release final 0.2.0 version of ALSA packages.
Documentation is very delayed (over one month to this time) :-((((

I'm sorry that my documentation (INSTALL, FAQ files etc.) isn't complete,
but I'm mainly programmer not writer and English isn't my native language.
I welcome any corrections...

> 3: What is the proper way to ajust the MIC Gain? Is there an easier way than
> editing the asound.conf? Why won't amixer do it? Is there an easier way?

Universal switch interface is new feature for 0.2.0 version of kernel.
Mixer switches are supported by XAmixer. If someone implements this
feature to amixer, I'll accept these changes.

> 4: What is the "MIC Gain" anyway? I don't see many references to it in 
> the driver source, but perhapse grep -i "mic gain" won't do it.
> Where would I get documentation on the GUSMAX especially its mixer or what
> source should I look at?

From datasheet for CS4231A:

LMGE	Left Mic Gain Enable: This bit enables the 20dB gain stage of the
        left mic input signal, LMIC.

RMGE    Right Mic Gain Enable: This bit enables the 20dB gain stage of the
        right mic input signal, RMIC.

ALSA driver controls these bits in functions
	 snd_cs4231_mic_gain_get
	 snd_cs4231_mic_gain_set
in alsa-driver/lowlevel/isa/cs4231.c source..

							Jaroslav

-----
Jaroslav Kysela <perex@jcu.cz>
Academic Computer Centre, University of South Bohemia
Branisovska 31, C. Budejovice, CZ-370 05 Czech Republic


