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Remote controlling an NAD C 320BEE amplifier #jukebox

๐Ÿ•๏ธŽ - 2021-07-14

For my jukebox I'm using an old(ish) NAD C 320BEE amplifier, which works fine except for one thing: when it is powered on, it starts up in "sleep mode", with no input selected and buzzing speakers.

Quite annoying, because I would like the Raspberry Pi to turn on the amplifier and (active) speakers when the jukebox is unpaused and turn them off when the sound is paused, using one of those nifty usb relays.

I noticed that the amplifier has an "IR in"-socket, so I started wondering if that could be used to control it.

And it can!

After looking at Pete Shadbolt's configuration (thanks!), I did this:

I found an old audio cable with a 3.5 mm jack in one end, and soldered two jumper wires to it, and connected the center of the jack to pin 22 on the Raspberry Pi and the top of the jack to a GND pin.

After rebooting the Raspberry Pi, I can now run commands like this:

jukebox:~$ irsend SEND_ONCE NAD_SR712 Input-Aux
jukebox:~$ irsend SEND_ONCE NAD_SR712 KEY_VOLUMEDOWN
jukebox:~$ irsend SEND_ONCE NAD_SR712 KEY_VOLUMEUP
jukebox:~$ irsend SEND_ONCE NAD_SR712 KEY_MUTE
jukebox:~$ irsend SEND_ONCE NAD_SR712 KEY_SLEEP

and the amplifier reacts. At least it does if I don't send them in too close succession.

To wake up the amplifier when I turn on the power, I have added a file /etc/systemd/system/amplifier.service with this in it:

[Unit]
Description=Set up amplifier
After=lircd.service

[Service]
Type=oneshot
RemainAfterExit=true
ExecStart=/home/asjo/bin/setup_amp
ExecStop=/usr/bin/irsend SEND_ONCE NAD_SR712 Input-Phono

[Install]
WantedBy=multi-user.target

And in the setup_amp script, I have:

#!/bin/sh

sleep 4s
irsend SEND_ONCE NAD_SR712 KEY_SLEEP
sleep 4s
irsend SEND_ONCE NAD_SR712 Input-Aux
sleep 4s
irsend SEND_ONCE NAD_SR712 Input-Aux
sleep 8s
irsend SEND_ONCE NAD_SR712 Input-Aux

As you can see, some fiddling with timing (and retrying) is prudent. And it works!

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