Electret mic to line level amp

[amdx]

I want to record the output of a stethoscope. I plan on connecting an
electret mic to the earpiece and amplifying the output to feed to a
recorder.
I have found a one transistor amp with 30 to 40 db gain,
but I don't have a transistor with hfe as high as the design(bc549c).
I'm looking for a two transistor design using 2n2222 or 2n4401. Most
designs I see have an opamp after the transistors. I just want a simple
circuit to raise the mic level to line.
Thanks for your help
Mike

 

[Rich Grise]

On Tue, 18 Jan 2005 18:17:52 +0000, amdx wrote:

I want to record the output of a stethoscope. I plan on connecting an
electret mic to the earpiece and amplifying the output to feed to a
recorder.
I have found a one transistor amp with 30 to 40 db gain,
but I don't have a transistor with hfe as high as the design(bc549c).
I'm looking for a two transistor design using 2n2222 or 2n4401. Most
designs I see have an opamp after the transistors. I just want a simple
circuit to raise the mic level to line.
Thanks for your help
Mike

Maybe one of these guys has some ideas:

http://www.google.com/search?q=mic+preamp+circuit
http://www.google.com/search?q=mic+preamp+design
http://www.google.com/search?q=mic+preamp+schematic

Good Luck!
Rich

 

[YD]

On Tue, 18 Jan 2005 18:17:52 GMT, "amdx" <amdx@worldnet.att.net>
wrote:

I want to record the output of a stethoscope. I plan on connecting an
electret mic to the earpiece and amplifying the output to feed to a
recorder.
I have found a one transistor amp with 30 to 40 db gain,
but I don't have a transistor with hfe as high as the design(bc549c).
I'm looking for a two transistor design using 2n2222 or 2n4401. Most
designs I see have an opamp after the transistors. I just want a simple
circuit to raise the mic level to line.
Thanks for your help
Mike

Look around in www.epanorama.net. May be something useful there.

- YD.

--
Remove HAT if replying by mail.

 

[Steve Parus]

http://sound.westhost.com/projects-8a.htm

On Tue, 18 Jan 2005 18:17:52 GMT, "amdx" <amdx@worldnet.att.net>
wrote:

electret mic to the earpiece and amplifying the output to feed to a
recorder.

 

[John Woodgate]

I read in sci.electronics.design that Steve Parus
<nospam.sparus@umich.edu> wrote (in <o4lvu05qj0o91imrtbtcfqgta0v266pgdg@
4ax.com&gt about 'Electret mic to line level amp', on Thu, 20 Jan 2005:

http://sound.westhost.com/projects-8a.htm

Project 13 Figure 1 looks OK. For transistors of lower beta than BC549C,
reduce R6 to 47 kohms. If necessary, adjust that value to get
symmetrical clipping of the output with a 1 kHz sine wave input signal.

Figure 2 appears to imply running the LM324 from 30 V, which is a bit
too close to the absolute maximum of 32 V for my liking in a homework
project.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk