Hello ALSA users I'm trying to find a way to increase the bias voltage of the analog mic input of my onboard ALC892 soundcard. The datasheet for ALC892 on page 9: http://www.hardwaresecrets.com/datasheets/ALC892-CG_DataSheet_1.3.pdf suggests the VREFOUT/MIC1 bias should be software selectable (2.5V/3.2V/4.0V) Default is ~2.5V, as confirmed when measured with a voltmeter. Digging deeper, I found in the HD-Audio.txt docs: https://www.kernel.org/doc/Documentation/sound/alsa/HD-Audio.txt that you can expose those controls in the snd-hda-intel by enabling 'add_jack_modes'. echo add_jack_modes=yes > /sys/class/sound/<CARD>/hints echo 1 > /sys/class/sound/<CARD>/reconfig and indeed it does: amixer -c SB controls numid=67,iface=MIXER,name='Rear Mic Jack Mode' amixer -c SB Simple mixer control 'Rear Mic Jack Mode',0 Capabilities: enum Items: 'Line In' 'Mic 50pc Bias' 'Mic 80pc Bias' Item0: 'Mic 80pc Bias' 80pc moves the default up by 0.7V, however I'd like to use the full 4V output if possible. Looking through the kernel source code for the driver shows a 100pc bias setting exists, but I am not sure how to enable it for my card because it's not a mixer option. Could anyone more knowledgeable point me in the right direction? Documentation on this is almost non-existent. Background: I have a EM183 cardioid electret capsule directly connected via the 3.5mm MIC IN jack. Unfortunately it needs +20dB to be audible and boosting it further increases the noise floor too much Since the data spec for the primo mic capsule suggests at least 3V, I'm guessing the 2V from the plug-in power isn't cutting it. So I thought I'd try increasing it first before getting a preamp else. ------------------------------------------------------------------------------ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
