Playing sound with `pyo.Mixer` on a specific channel

I want to be able to play a sound on multiple channels of a sound card and I’m using pyo to trying to code this. I decided to use the pyo.Mixer to exactly define on which channel a sound should be played, but I’m failing already at implementing this in a minimal example only using pyo.

from pyo import *

s = Server().boot()
s1 = Sine(freq=440)
mixer = Mixer(outs=1,chnls=2)
mixer.addInput("sound 1",s1)
# play sound 1 on chnl 1 with full volume
mixer.setAmp("sound 1" ,1 , 1)

If I understand the Mixer correctly I only need one output, because I don’t want to process the sound any further only play it on one of the two channels. To test this I’m using my headphones plugged in and I’m actually able to play sound by executing:


I’ve also played a bit with all parameters and if I set the channel to 0 in

mixer.setAmp("sound 1" ,0 , 1)

the sound is played on both headphones, but the inputs 1 or 2 are producing no sound at all.

Am I missing something basic or using the Mixer in a wrong way?