I'm sorry if this is the wrong area for this, but I'm new to this, so please bare with me.

I'm looking for a circuit for a differential OP-Amp, that is caperbile of working with a mic of 5 Ohm with an output level of 1.4-4 uv ?

I've built quiet a few 741 based op amps and these have been successful in the past, but the characteristics of this mic mean that the pre-amps I've built in the past are not satisfactory and I need a little help.


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No thanks, I'll keep my pants on. :-)

Ribbon mike? Those can be tricky. Even low-noise opamps will have trouble giving good performance. Designs that I have seen typically use an external matched pair of transistors running at fairly high current as the first stage (for ultra low noise) and then a low-noise opamp for the bulk of the gain.

Wow, you really need to check out some of the more modern technology. We've come a long way in the last 35 years!

-- Dave Tweed

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David Tweed

If you wish :)

No its not a ribbon mice, its a dynamic one, Electrvoice M-87/AIC as used on Helicopter headsets.

Ahh, but if it aint broke...

The actual application is to take a Sennheiser HMDC372 headset and make it work acceptably with a signtronics intercom, the intercom is really great and has a lot of nice features, unfortunably it expects to have much higher input that the Sennheisers can provide.

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Need more input!!! What impedance will the preamp be working into? What audio level do you need from the preamp? What DC supply voltage(s) do you have to work with? Obviously, hi-fidelity isn't a concern, but what's the expected frequency range?

Dave M
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