This has been a boggling problem for me for a while. I hope someone here has a clue of what's going on here.
I am using an Mini-TOSLINK to TOSLINK
cable between my MacBook (First Unibody model)
and my Yamaha HTR-5940
receiver. The receiver feeds a pair of Klipcsh Quintet SL
main L/R speakers and a Pinnacle Digital Sub 100
with a mono RCA connection. This is my computer speaker set-up.
I keep my receiver on "STRAIGHT" setting. No other audio setting scheme changes this problem either. The sub comes through great under -30dB on the receiver.
Also, the volume level on the MacBook is a fixed output level once you connect an optical connection.
When I increase the volume upwards of -30dB
my subwoofer volume seems to stop increasing proportionately with the main L/R speakers.
Let me add that when I was using this same equipment with a different connection method with my PC this problem never happened. That other connection was the multi-channel analog output of the sound card which is 3 3.5mm outputs carrying 2 channels each which plugged into the receiver with stereo RCA connections on the other end. The subwoofer would always increase in volume equally to the mains.
If anyone has any thoughts on what might be going on please let me know.