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Re: Mic/Earphone Headsets

Andreas-

Thanks a lot!  I rigged a little system to test your theory, and YES, it
worked.  I put a single AA battery in series with the microphone, and it
worked.  I got some low freequency feedthrough, but I suspect that
shielded cables will take care of that.

The only problem is that the gain through the preamp seems a bit low,
but I'll see what I can do about that.

Cheers,
Bruce

Andreas Schenk wrote:
> 
> Bruce Chadwick <nospam.bpc1@columbia.edu> wrote:
> : However, I can't get any sound from the microphone into the computer.
> : Strangely, if I send the earphone jack (this one is 1/8") through the
> : pre-amp and into the computer, I can talk into the earphone and get the
> : sort of sound from that I wanted from the microphone, but the mic itself
> : doesn't give me anything.  I've checked connections, and I've checked
> : the headset with the TalkAbouts in the store, there are no broken
> : circuits as far as I can tell.  Could it be that the microphone needs
> : juice put in from somewhere?
> 
> That's what I guess, too. I once had a similar headset with earphones
> and a microphone. It required either phantom power from a mixer/preamp
> (perhaps phantom power is switchable at your preamp) or, if phantom
> power is not available, you could use a sort of connector, which
> contained a 1.5 V Lithium Battery as a power supply for the mic.
> It is wired like this :
> 
> ----------- [ Lithium Battery ] ----------------------
>                                                      I
>                                                      ----
>                                                         Mic
>                                                      ----
>                                                      I
> ------------------------------------------------------
> 
> It is directly in series with the microphone. Maybe you'll need 3
> Volts, it can depend on the type of the mic.
> To get the right polarity of the Battery, just try, it shouldn't spoil
> anything.
> The direct current from the battery has no influence on the preamp, as
> the preamp is only amplifying alternating currents.
> I used the wiring above to build some cheap headsets for Gigs with
> Rockbands. Although it were sound systems in Germany, it should work
> for you as well.
> 
> Viele Grueslies,
> 
> Andi
> 
> ----------------------------------------------------------------
> In a world without fences, who needs GATES ???

-- 
Bruce P. Chadwick
Columbia University

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