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Re: Warning: Bad MD mic inputs

Subject: Re: Warning: Bad MD mic inputs
From: Dan Dugan <>
Date: Mon, 23 Aug 2004 11:22:38 -0700
>To my surprise, the three models I have of Sharp MD's from last year, give
>only 0,4 - 0,45 v plug in power voltage. It's 1,2 - 1,4 without load, but
>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 explanation.
>So: Dont buy any of the "last years" Sharp MD's. The models I have tested
>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


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