The A-138c Polarizing Mixer can be used as a manual voltage source;
to
quote from the module description:

"Control In1 works as a DC offset generator (about -5V...+5V)
provided
that no patch cord is plugged into socket In1"

This is a great feature. While I realize that the A-133 is designed
to
act upon external voltages, can the manual pot of the A-133 be used
in
similar fashion to the A-138c if no voltage is plugged into its
signal
input

Thanks,

Chris