Orange Pi [PC+/Zero] MIC1 boost AMP gain control

Hello!

I have:

1) Orange Pi PC+ with ARMBIAN 5.38 stable Ubuntu 16.04.5 LTS 3.4.113-sun8i

2) Orange Pi Zero with ARMBIAN 5.60 stable Ubuntu 16.04.5 LTS 3.4.113-sun8i

3) Orange Pi PC with Debian 3.4.39 #1 SMP PREEMPT Wed Sep 16 13:39:07 CEST 2015 armv7l

On both ARMBIANs I have noticed: every start of arecord sets level on "MIC1 boost AMP gain control"  audio setting with constant value 5.

I think it uses value of "cap_vol=5" from section [audio0] from script.bin.

On Debian it does not.

In my case I need very very very low value of "MIC1 boost AMP gain control".

Value of "ADC input gain ctrl" is already 0.

Any ideas what is responsible: alsa, driver or something else?

And how to avoid that?

The way to repeat:

1) with amixer see current value of "MIC1 boost AMP gain control" - in my case 5.

2) set any another value: amixer sset "MIC1 boost AMP gain control" 4

3) check new value 4 with amixer

4) start arecord to record anything

5) check value of "MIC1 boost AMP gain control" with amixer: it got 5 again