Turning guitar effects into vocal (xlr) effects

[ianmgull]

So while staring blankly at a tray of ferric chloride slowly eating delicious copper for the better part of 30 minutes I got to thinking. What sort of changes (if any) would have to be implemented to turn guitar effects into vocal effects? Obviously you would have to deal with xlr connections, but anything else? I know the impedance's  are different so would that require a different type of buffer? Any other general suggestions to look out for?

ian

[earthtonesaudio]

Not too bad, only 2 big issues, and one small one.

Big issue 1: balanced inputs and outputs.  This can be solved in a quick and dirty way by just grounding the out-of-phase input at the input buffer stage, running the in-phase signal through the effect, and making the outputs balanced using a dual op-amp buffer.  One inverting and one non-inverting output, each goes to the respective pin of the XLR jack.  I think this is called "half duplex" but I'm not sure.  There are several ways to do this.  Look for info on "balanced outputs." 

Big issue 2: impedance matching.  Not too bad, if you make sure there's buffers going into and coming out of your effect.  Keep in mind that microphones vary a lot in output impedance, and it might be a good plan to make the input have selectable impedances to match different mics.

Small issue: the frequency response in guitar effects is *usually* optimized for guitar, so vocals might sound a little telephone-like.  But then again, that might not bother you.

[william]

Another option would be to build a stompbox interface that has a balanced input into a summing amp, then out to the effect Then a second input coming from the effect out to a balanced output.  Kudos if it can be powered using phantom power from the mixer board.

[Paul Perry (Frostwave)]

Probably the most famous case of a guitar effect being used for vocals, was the Gristleizer.
I see ring modulators in use too. Good with a rocker foot pedal controlling the carrier oscillator.
Something to watch: the audio signal may be very low, compared to a guitar (if you have a dynamic mic).
Those hi/low impedance transformers will take care of it usually.

[Processaurus]

Another option would be to build a stompbox interface that has a balanced input into a summing amp, then out to the effect Then a second input coming from the effect out to a balanced output.  Kudos if it can be powered using phantom power from the mixer board.

I want one too!

http://www.diystompboxes.com/smfforum/index.php?topic=61419.0

This chip looks helpful:
http://www.analog.com/UploadedFiles/Data_Sheets/SSM2019.pdf