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Rasing input/output via amixer and saving settings

Michael Dessen

February 04, 2021 03:51

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I'm using a DAC+ADC Pro on a RPi 4 in order to use low latency music performance software (specifically an app called Sonobus, as set up on this image, jambox-pi-gen: <https://github.com/kdoren/jambox-pi-gen>). Jack is used in Sonobus for audio. I'm having trouble getting enough input/output (with a dynamic mic, connected directly to the mini-jack input), so I experimented with the PGA Gain Left/Right  settings and raising those to the max (40db) enabled me to get good input levels. But I have a few questions/problems:

1. If I use amixer to set the PGA Gain levels instead of alsamixer, I get distortion (high pitched noise) as soon as they go above 0dB. Any idea why this is?

2. After making those PGA Gain changes in alsamixer, I can't seem to save them as I'd expect with the command

sudo alsactl store

That command returns this:

ALSA lib conf.c:1887: (_snd_config_load_with_include) toplevel:349:30:Unexpected char

Any idea how I can save these settings so I don't have to reset them each time?

Alternately, if there is a better way (than PGA Gain levels) I should use to increase the input/output settings please let me know. With the mics/headphones we're using, it just wasn't even close, because we're trying to avoid going through a headphone amplifier and coming straight from a dynamic mic. This is for mulitple kits for students and we're trying to minimize gear so I'm hoping I can solve this with the device hardware or software settings rather than add more audio equipment in the input or output paths.

Thanks!

Michael

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4 comments

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  HiFiBerry team February 04, 2021 06:03

  The alsacontrol store problem is a bug in the alsa utils. This has been fixed a long time ago already (i think at least 6-10 months), but many distributions still seem to use the older versions. You would need to download and compoile the latest alsa-utils.
  
  amixer and alsamixer should work exactly the same. We haven't seen the behavior that you're talking about. Unfortunately I can't say what might causing this.

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  Michael Dessen February 04, 2021 06:10

  Thank you! In the meantime (I'm using a distro mentioned above) is there not any way I can manually override it so that the correct setting is set each time on startup, like a startup script? Sorry this is over my head but if there is a way to point me in the right direction I could try to figure it out. Either way, thanks again.

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  HiFiBerry team February 04, 2021 06:12

  You can just put the right amixer commands into a startup file. I don't know the distribution mentioned above. Therefore it's probably best to ask the developers if there is already a file that can be used for this.

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  Michael Dessen February 04, 2021 06:13

  Okay, thanks.