Stock IVP input scheme:

My idea for adding a rear input jack:

What it will look like going in from the front:

What it will look like going in from the rear:

So my question is whether or not this is a stupid way to do this. Basically, I want the insertion of a TS jack into the rear TRS input to turn off the front input so I don't have to worry about one input loading the other and volume issues and so forth associated with passively summing the front and rear signals. The only problem is that the best way I think I can do this is in the manner shown above, which creates a voltage divider for the front input so the volume will effectively be halved. I suppose I have enough gain to make up for that, but there's something unsatisfying about the first front input and the rear input being more special than the second front input because they don't have the volume loss. I'm also a little concerned about the 2M resistor being in series with the second front input might have some impedance issues that I'm not expecting and actually end up attenuating the signal far more than just by half.

I had another idea involving a MOSFET to effectively turn the second front input off upon a TS jack being inserted into the rear, but I don't know where to find a voltage source on the IVP that I can short to ground without screwing everything else up and also not sink a lot of current.

I think working with passive components is probably going to be much simplier in this case, and maybe there's something really obvious that I've totally missed.

By the way, all the schematics you see here were generated using XCircuit, which is available at http://opencircuitdesign.com/xcircuit/.

It worked exactly as planned.

edit: By the way, I may have mentioned this before, but the insulation on the power cord, at least on my unit, was incredibly flaky, so if you're doing any work inside, it would probably be a good idea to replace it lest you inadvertently create a short or something.

Could you not use a normalling-cabapable jack socket on the front (or rear) and have the front socket normalled to the rear unless there is a jack present at the front?

Rodabod wrote:Could you not use a normalling-cabapable jack socket on the front (or rear) and have the front socket normalled to the rear unless there is a jack present at the front?

Exactly what I was going to suggest, but if what you did works to your liking, I guess it's no big deal.

This is exactly the kind of advice I expected to find here. I had never heard of normalling before this thread, but it turned out that I happened to have a Switchcraft 112AX lying around, so I hooked it up the way the internet told me to and now I don't have to suffer volume loss on the front input. Thanks, EA!

Which plan did you go with?