Simultaneous Parallels to Balanced and Unbalanced Inputs

[Steamy Williams]

I have a compressor with unbalanced side chain inputs, but because this was a custom modification the side chain switches are on the back. I was hoping to avoiding going round the back of the racks to access the switches, and to leave the switches set to external side chain, and then just parallel an output on the patchbay (to both the balanced main input and the unbalanced side chain input) whenever I want the side chain to see the same signal as the main inputs.

All of the balanced outputs in my studio are either transformer-balanced or quasi-floating electronically balanced, so it makes sense for the connection between the unbalanced side chain inputs and the patchbay to have the cold tied to ground. However, is it going to be possible to parallel an output to both sets of inputs with no difference in the level (i.e. 6dB) between the signal at both inputs - and whilst keeping the signal balanced going into the main inputs?

[David Kulka]

It's generally not a good idea to parallel unbalanced inputs with balanced ones. Since the signal feeding it will have different loads on the hot and cold legs, common mode rejection will be compromised. We do this sometimes with timecode and headphone amp feeds, but unless you're desparate, I'd avoid it.

You could use a Matchbox or some other kind of balanced to unbalanced converter in front of your side chain in, then you'd be feeding 2 balanced inputs, which would be fine. Another workaround would be to use some idle piece of balanced gear like a limiter or EQ, or a DAT in input monitor, as a buffer. Mult into the piece of buffer gear, then connect the unit's out to your unbalanced sidechain in. Not ideal, but it's a work around that would solve the main problem.

[Matt Syson]

Hi
As it is a sidechain imput you could use a cheaper transformer to balance it up. Make sure it can handle the notmal levels though without excessive distortion.
Matt S