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Re: Warning: Bad MD mic inputs

Subject: Re: Warning: Bad MD mic inputs
From: Klas Strandberg <>
Date: Mon, 23 Aug 2004 21:50:47 +0200
I fear that the input FET IC with resistor and capacitopr is integrated
with the chip.
A quick look into it gave that there is enough space for an extra resistor=

and capacitor. I have to buy them to test, as I never use this "micro" size=

The MD's I talk about has 1,5V battery voltage. Even so, the previous 1,5v=

Sharps had 1,2v at the input, loaded.
No risk, the voltmeter used only give some 10 Mohm load


At 20:22 2004-08-23, you wrote:
> >To my surprise, the three models I have of Sharp MD's from last year, gi=
> >only 0,4 - 0,45 v plug in power voltage. It's 1,2 - 1,4 without load, bu=
> >drops as soon as you connect the mic to it.
> >Such a low voltage is not enough.
> >I have contacted Sharp support, but I don't hope for any good explanatio=
> >
> >So: Dont buy any of the "last years" Sharp MD's. The models I have teste=
> >are: (European) MT190H, MT290H and DR580H.
>Interesting, that seems awfully low. I checked a classic Sharp 722
>with a Shure 183: 4.0V open circuit, 3.4V with mic connected.
>It would be easy, theoretically, to put in a lower value current
>limit resistor in the input circuit, but the miniaturization might
>make it very difficult in practice. I also wonder if the resistor is
>so high that an ordinary voltmeter loads it down. You might check to
>see if the unloaded voltage appears higher with an electronic
>voltmeter or an oscilloscope. I guess in a single-cell powered device
>1.5V is as high as you get...a case for an external plug-in-power box.
>-Dan Dugan
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links

Telinga Microphones, Botarbo,
S-748 96 Tobo, Sweden.
Phone & fax int + 295 310 01


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