E-Mu Vintage Keys Operation Manual page 27

If you insert a stereo plug into one of the Sub Outputs, the ring of the plug
serves as a signal Return which sums into the Main outputs.
Therefore, the Sub 1 jacks can serve as effect sends and returns
in order to further process selected instruments and then
return them to the main mix.
You can use the Sub 1 jacks as send/returns in order to further process
selected Vintage Keys presets without using the effects bus on the mixing
board. In a pinch, the effect returns can be used to sum additional instru-
ments into the main outputs. It's like having an extra line mixer when you
need more inputs!
Output Section
R Bus
Tip
You can use the Sub 1 jacks as effect returns to the Main Outputs.
Note that the Effects Processors are only routed to the Main Outputs.
Processors
L Bus
Tip
Ring Ring
R L
SUB 1
Studio Setup
Effects
R L
MAINS
Vintage Keys Operation Manual 17
Setup