Is the L on the mixer channels the same as dim?
No. Listen bus is a solo system that don’t breaks the routing to the master bus…
Like the solo system in live sound environments… a PFL so to say… with more possibilities to configure it
If you have an FX channel, for example, and you send a guitar to it, if you solo the channel, you will hear the guitar and the FX. If you L the channel, you will hear mainly the FX. The guitar will be heard, but dimed. The amount of dim can be set up in the Control Room. Personally I set up this dim very low (I believe it is -inf). This way, when I L the channel, I hear only the FX, but no guitar at all.
There are 2 ‘Dim’ functions in the Control Room. One controls the amount of Dim when using Talkback, the other controls the amount of Dim when using Listen. The L button on the Channel engages this second Dim.