PTT Box

[dannyn]

Does anyone have a good schematic for building a push to talk box with xlr in and out?

Thank you.

[mbenonis]

Not offhand, but I bet you could come up with one pretty quickly. Basically, I would recommend the switch be a DPDT switch, with the on terminal connecting the input to the output and the off terminal grounded to avoid pops and clicks. Give it a shot and see if it works!

[Chris15]

Originally Posted by mbenonis

Not offhand, but I bet you could come up with one pretty quickly. Basically, I would recommend the switch be a DPDT switch, with the on terminal connecting the input to the output and the off terminal grounded to avoid pops and clicks. Give it a shot and see if it works!

Mike Mike Mike Mike Mike...
I'd have expected better of you.
If you are going to use Mike's approach you need to do some coupling workarounds to not go destroying things when phantom power comes into the mix... Namely a diode bypassing the switch and a decoupling cap on the output side of the switch, for each of the hot and cold legs...

Or use the easier approach. Loop the signal in and through. Insert switch between pin 2 & 3 (SPST switching is all that is needed). This shorts the signal so you get no audio (assuming the CMRR of the input is reasonable) but don't stuff up any phantom...

[mbenonis]

I stand corrected...I felt a bit odd about my solution but I couldn't put my finger on it. Chris15's solution of tying pins 2 and 3 together is a MUCH better one and I highly recommend it.

Recall that a balanced input stage looks for a voltage difference *between* pins two and three, and amplifies it. Thus, by shorting the pins together, there is no ac differential and thus the signal is turned off.

Thus, don't do what I suggested above!

[dannyn]

Hello guys,
Thank you for the prompt responses. I forgot that this forum does not email you when you are posting in a thread, I need to go change my settings on that one.

I will try that and see how that works.

Again thanks.

[Chris15]

Oops, just remembered... What I described is really a push to mute circuit, so if you are using a push button to achieve PTT, you need a normally closed switch...