Simple Microphone Preamplifier

[polygyne]

Hi everyone.. first post here!

I am breadboarding the Simple Mic Pre which is found on Tomi's audio circuits page. I want to use this for feeding a stereo tie clip electret mic into a minidisc walkman recorder which only has a line input.

I've tried building the circuit and it sounds fine for my purposes , albeit in mono.

So I plan to use two of these circuits side by side for stereo use , but I would like to know if I can run them both from a single 9v battery , or if it would be better to use two batteries , one for each circuit.

When I build this into a metal enclosure , I'd like to keep it as small as possible, for convenience, which is why it would be nice if I could get away with using only the one pp3, even if that means higher consumption and needing to change battery more often.

My main concern is whether this two of these circuits can be paralled like this , or if I'd need to add any extra buffering /decoupling etc..

I'd appreciate any thoughts on this!

Many thanks

P

[Tomi Engdahl]

I am breadboarding the Simple Mic Pre which is found on Tomi's audio circuits page.

You must be referring to this circuit:
Simple microphone preamplifier
http://www.epanorama.net/circuits/micamp.html

I want to use this for feeding a stereo tie clip electret mic into a minidisc walkman recorder which only has a line input.

I've tried building the circuit and it sounds fine for my purposes , albeit in mono.

So I plan to use two of these circuits side by side for stereo use , but I would like to know if I can run them both from a single 9v battery , or if it would be better to use two batteries , one for each circuit.

I think two of those circuits should work pretty well from one 9V battery.

My main concern is whether this two of these circuits can be paralled like this , or if I'd need to add any extra buffering /decoupling etc..

There is already a quite powerful decoupling network on the the power input of the circuit, consisting of 120 ohm resistor and 100 uF capacitor. I don't think you would not need to add anything more for this.

[polygyne]

Hi tomi!

Many thanks for the info..that's good news!

can I ask one further question...

If the electret microphone being used is already powered,say e.g. the type that takes an AA battery inside the mic body , then presumably this mic would be connected to the unpowered 'dynamic in' socket instead....? If so, should any resistance be added to pad the level down?

Or could it be possible to make the power to the 'electret' input switchable on/off?

Cheers

P

[Tomi Engdahl]

If the electret microphone being used is already powered,say e.g. the type that takes an AA battery inside the mic body , then presumably this mic would be connected to the unpowered 'dynamic in' socket instead....?

That should work well.

Or could it be possible to make the power to the 'electret' input switchable on/off?

That's possible as well. The resistor R1 supplies the power to the electret mic input.
Just add a switch in series with it and you have the power switchable on/off on electret input.