Max amplitude is low

[moggyd]

Hi

Have been playing with this board again - have it all working fine but the aplitude of the recordings is low compared to my PC and another sound card I have for the pi.

e.g. with a line in source
ffmpeg -f alsa -i hw:0,0 -t 30 out.flac

creates the file fine, but when viewed in Audacity the max/min values are 0.5 and -0.5 rather than recordings from other cards which have max 1.0 and min -1.0.

Is there some amixer magic I need to do to fix this?

Thanks

[flatmax]

If you can boost in alsamixer, that would be your best choice.
Alternatively, the Audioinjector Zero doesn't have 6 db limiters on input, it is another option.

Matt

[moggyd]

OK I can now record with full range. Got it working with a custom .asoundrc file listed below. This gives an extra slider labelled "inboost" in alsamixer. I set it to max and adjusted down using the hardware input control - that way it should be able to deal with lower input levels like turntables.

BTW I had to enable "ADC High Pass Filter" otherwise there was a massive DC offset. What does this setting do exactly?

pcm.!default {
type asym
capture.pcm
{
type plug
slave.pcm "softvol"
}
playback.pcm
{
type plug
slave.pcm "dmix"
}
}

pcm.softvol {
type softvol
slave.pcm "dsnoop"
control { name "inboost"; card 0; }
max_dB 16.0
}

ctl.!default {
type hw
card 0
}

[jessecobra]

Alternatively, the Audioinjector Zero doesn't have 6 db limiters on input, it is another option.

Do you have this documented somewhere?

[flatmax]

Where do you think is a good place to document this ?

Matt

[robiwan]

If you can boost in alsamixer, that would be your best choice.
Alternatively, the Audioinjector Zero doesn't have 6 db limiters on input, it is another option.

Matt

Matt, is there a way to tell whether it is a Zero or fullsize WM8731 card that is attached, to be able to apply the softvol boost only in the case of the latter ? Also, regarding the 6 dB limiter, is it possible to remove it ?

[jessecobra]

Where do you think is a good place to document this ?

Matt

On this forum of course!