Linkplay/amplifier-adjust.md

# Adjust Gain in Amplifier
A while ago I bought 3 Up2Stream Amp v2 devices (v1.1 is printed on the pcb). They are working well, but I have a problem with the power control with the one that is installed in my Sauna. When I'm relaxing there I'd like to hear soft music or nature sounds, but even at volume level 1 (on a scale from 1-100) it's a bit too loud and its difficult to use the slider in the app when you only need values 1-5, but not the rest from 6-99. I have asked Arylic support and they were really friendly and explained a way to solve my problem: you can swap resistors, and that will adjust the gain of the amplifier directly. You can refer to the specifications of amplifier chip TI3116 from Texas Instruments.

See data sheet https://www.ti.com/product/TPA3116D2

In chapter 7.3 Feature Description, especially 7.3.1 Gain Setting and Master and Slave you find the following information:

| Mode   | Gain   | R1    |  R2   | Impedance
|-----------------------------------------
| Master | 20dB   | 5.6k  | open  | 60k
| Master | 26dB   | 20k   | 100k  | 30k (default setting for Arylic PCB)
| Master | 32dB   | 39k   | 100k  | 15k

R1 in TPA3116D2 data sheet is R19 in Arylic PCB and R2 is R18




To set and verify volume control, use these API commands:
```
# set volume to e.g. 1:
curl 'http://10.1.1.52/httpapi.asp?command=setPlayerCmd:vol:1'
 
# show volume:
curl -s 'http://10.1.1.52/httpapi.asp?command=getPlayerStatus' | jq
``` 
See https://developer.arylic.com/httpapi/#adjusting-volume