Mute button on Analog 1/2 does NOT work

[apathetic]

I have audio from my computer which I'm sending out to (digital) Audio Out 1 & 2, while at the same time I also have random music/noise being sent to (analog) Audio In 1 & 2. However, I do NOT want to monitor the random music coming in -- I just want to hear audio sent from the computer -- and I'm trying to disable audio input on channels "In A1" and "In A2". I've muted both "In A1" and "In A2" and put the volume to zero. However, I'm still hearing audio sent into the analog inputs of the device being passed through to the output. Why?