Re: Realtek AC97 outputs very low

In article <1134669948.904215.5150@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, "song"
<song.ahn@xxxxxxxxx> wrote:

> I have A8V deluxe and have a problem with onboard Realtek sound
> chipset. Suddenly, the line-out volume became very low.
>
> I leveled max both volume and wave out controls, but the signal is not
> strong enough. It is more likely under medium output as compared
> before. I usually listen music through headphone. And it is a little
> annoying because I have to hear low sound all the time.
>
> Is there a hidden setting to increase output gain? Did I fry the
> amplifier ? (I am sure even it has a amp)
> Thanks.
> ==song==

According to the ALC850 datasheet, both the "front-out" and
"surround" have amplifiers capable of driving a 20 ohm load
to 1 volt. That would traditionally be suitable for driving
headphones (at least some headphones are a lighter load
than that, at 32 ohms - higher ohms is lighter).

In the AC97 register interface, there are two options for
both amplifiers. The output can be turned off completely, or
the amplifier modules can be bypassed. With the amplifier
bypassed, it has the driving strength of say, the
center/sub output. Somewhere between 200 ohms and 1000 ohms,
which is very weak, and is most suited to driving the input
on amplified computer speakers. In that state, if you
connect headphones, the output would be barely audible.

The ALC850 has universal audio jack detection. When you
plug in the headphones, does the Realtek driver recognize
that headphones have been plugged in ? Make sure that when
you do plug them in, the software is set up to drive "headphones"
and not "computer speakers". It is possible that one of those
software selections, would cause the amplifiers to be bypassed.

(PDF page 38, MX7A bit 6 set to 1, makes headphones weak.)

ftp://210.51.181.211/pc/ac97/alc850/ALC850_DataSheet_1.4.pdf

1) Make sure that if jack sensing is enabled, and a dialog box
pops up to verify what was plugged in, that the software
is told they are "headphones".
2) Try driving the headphones from the Surround output instead.
Some audio control panel software has a "cloning" mode, where
the same stereo signal, can be fed to more than one output jack.
See if the Realtek software supports that.

You might have a look around, and see if a later AC97 driver is
available for the ALC850.

The current driver version at RealTek is A3.80 . This is a
_big_ download. RealTek download servers are usually pretty
slow, so try all three and see which one is faster. Uninstall
the old driver, and try a newer one.

http://www.realtek.com.tw/downloads/dlac97-2.aspx?lineid=5&famid=12&series=8&Software=True

HTH,
Paul
.

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