Hi dirtylarry,
There is no simple way to add tone controls to Rune. The way Rune works is to provide bit-perfect reproduction of digitally encoded sound.
Digital route:
Digital tone controls can be added using brutefir (search the forum for details). There is also an unfinished project attempting to do this on the Volumio forum, it’s worth a look. A second partial solution is also available for streaming Apple AirPlay, you can do this by replacing shairport by shareport-sync (see the forum for details). Shairport-sync also has functionality equivalent to brutefir. P.S. brutefir is not designed for tone controls, but can do it. Also please note that brutefir is very complex!
Analogue route:
Your sainsmart xs400 sound card has a DAC plus an analogue amplifier. There are jumpers to enable the amplifier. It could be possible to tap-off the DAC output, feed it through a tone control network and then feed the output back into the amplifier input. You should first contact the supplier about this. Replacing the existing volume control (the volume control is then the tap-off point) with something like this:
https://www.ebay.com/itm/HIFI-Amplifier ... SwWflaLRCF would probably work. Safely desoldering the existing volume control will be a challenge, and this would certainly invalidate your warranty.
janui
