Batboard

Can someone point me in the right direction for a small simple pre-amp that I can power from the mic bias on a GM338 to work with a dynamic microphone element (200 ohm)

Thank you in advance
Mike

setcom has a preamp for about $100.00 that is matching for your mic element .. about $100.00 or you can build your own using a 2n3904 utilizing a 150 ohm i/p and a 1 K ohm output ..

CircleBat wrote:setcom has a preamp for about $100.00 that is matching for your mic element .. about $100.00 or you can build your own using a 2n3904 utilizing a 150 ohm i/p and a 1 K ohm output ..

Design in electronics not my forte but I will do some googling based on that transistor and see if I can find something

Thanks for the tip circlebat

It's been a while since I pushed electrons rather than bits, but look for a self-biased common-emitter amp for an NPN transistor. Any NPN will do, the 2N3904 is just dirt common.

How well do you guys think the amp out of a mobile mic would work? I'm thinking take the electret element and it's bias circuit out and connect the dynamic mic instead.

Looks like it would be simple enough on something like these:

http://www.repeater-builder.com/motorol ... n1052a.jpg
http://www.repeater-builder.com/maxtrac ... n3596a.jpg

Not sure what kind of level you'd get, or how it would sound... but I figured I'd throw the idea out there if anyone wants to tinker.
You should be able to pick up junk mics with working guts for free or cheap.

Those mic amps will not have enough gain for the dynamic element. You would need to add a stage.

I remember using a NPN transistor driving a PNP transistor for the older dynamic elements.
I can email a sketch if someone can post it here.

pay the 100 bucks for this amp...it will work

Will wrote:Those mic amps will not have enough gain for the dynamic element. You would need to add a stage.

I remember using a NPN transistor driving a PNP transistor for the older dynamic elements.
I can email a sketch if someone can post it here.

Will
I am happy to put your sketch together in a cad schematic program and if. Can work it all out post it either directly or throw it up somewhere in cyber and

Ryes
Mike

The old David Clark headsets with a dynamic mic have an amp that I have used for other mics with good results. PM me your address and I will send you one from a broken mic.

I sent Mike the preamp diagram in the email. If anyone wants it it is available by email.

Maybe some can put the diagram in this topic.