How to isolate mic in talkback box?

[elskardio]

Hi,

I built a small talkback box for my studio using Igor's talkback combiner schematic.

Everything works fine... but every time I press the switch the microphone picks up the clicking sound from the switch. And it's not very pleasant with headphones at high volume  :-\

Is there a good way to isolate the microphone from the enclosure's vibrations?

I know I could use an external mic but I really like my little box 

Thanks

 

[Gareth Connor]

The short and unhelpful answer is no because there will always be a mechanical connection between the mic and whatever is holding it in place.

This is a problem that has plagued console manufacturers for as long as small/sensitive/electret/built-in microphones have been used for talkback. There are, however, ways to reduce the effect, both mechanical and electrical.

Soft material mounting of the mic. Pop-shield foam or similar is a way of soft-mounting the mic.
Use of very light weight cable (lavalier mic cable) to reduce mechanical coupling through the cable between the mic and the rest of the TB box.
Use a mechanically silent/quiet switch. Be prepared to pay a bit more for such a switch.
Delayed switching of the mic's audio. Insert a small delay circuit between the TB switch and the audio switch that routes the mic signal (to wherever it's going). 100mS is probably long enough for the audible mechanical "KLUNK" of the switch to dissipate before the mic's audio is switched on...... and avoid using a relay for switching (or at least choose carefully), because relays can also be mechanically noisy, which just moves the problem to another location.
Enclose the mic in some form of mini-container so as to reduce direct acoustic coupling with the switch.

There are more ways, but this collection is typical of the more common methods. Used in combination will often yield cumulative improvements.

 

[RuudNL]

Don't make the delay too long... (As was the case in my Mackie 'Big Knob', I always lost the first word!)

 

[elskardio]

Thanks Gareth for the recommendations ! I will revise the way the microphone is mounted in my enclosure.

A small time delay is a good idea! Do you have a simple circuit in mind? I guess I could use a 555 IC...

The switch is turning ON/OFF 15V DC in the circuit.

Thanks again

 

[peterc]

You could use a touch plate switch to flip a relay...... Nice solution, I reckon.

http://pcbheaven.com/circuitpages/Resistance_Touch_Button/

is a nice example

Peter