Switching jack for a line in to output stage?

[ShoemanGB]

That Hilton PA rig I have has an output jack just before the PI that was used to run a second PA as a slave. I don't need that, but I was wondering if there is a switching jack that I could install there that would ground the preamp output and let me run a line in to the PI/Output stage?   I could install a simple jack and a switch but I like having the preamp go to ground without having to remember to throw a switch.
That would allow me to use my rackmount preamps with the Hiltons dual 6L6 for fun. 

[thetragichero]

yes, it's basically a passive effects loop without the effects send. shunt tip jack right before the phase inverter

[sluckey]

You need a Switchcraft type 13 isolated switch jack.

     https://www.tubesandmore.com/products/14-jack-switchcraft-mono-isolated-make-circuit

[ShoemanGB]

Nice!  Thanks for the info guys.  I knew someone would have the scoop.  Never seen that jack before. Very interesting.

[sluckey]

Why do you care if the preamp is grounded? A simple two jack pre out/ext pre in is twice as versatile. Like this...

     http://sluckeyamps.com/november/november.pdf

Or if you really only care about an ext pre in, this works very well...

     http://sluckeyamps.com/vox/Vox.pdf

[ShoemanGB]

I was under the impression it should be, but if it does not need to be and can idle with no input while i use the power amp section, that simplifies things.  So is it OK to simply disconnect the pre from the PI and leave the Pre output "floating" for lack of a better word?   

[sluckey]

Yes. The output is "floating" but if nothing is plugged into the inputs, it should not matter. Especially if you have input jacks that short the input when nothing is plugged in, like the example schematics I posted.