From: "Jim Shorney" 
Subject: Re: e: [drakelist] T4XC and D104


"Jim Shorney"  made an utterence to
the drakelist gang
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On Wed, 04 Aug 2004 21:18:47 -0700, Grant Youngman wrote:

>Impedance matching is in part the reason for the preamp in the first 
>place.  Except that even the Astatic preamp doesn't have a high 
>enough input impedance to get the D-104 to sound as good as it 
>can.  That can be fixed by simply increasing the value of the input 
>resistor on the preamp.  Many alternate simple preamp designs, 
>some with variable input Z to allow tailoring of the mic's response 
>are around also.


If that's the case (and I'm not doubting anyone's word here), it should
be a simple matter to brew up a good low-noise op-amp configured as a
unity gain amplifier with a suitably high input Z. Hang a pot across
the output to attenuate in case the mic output is too high for those
newer rigs. This I could be comfortable with. No need for a pre-AMP, in
any case. Just a Z-matching buffer.

-- 
Jim Shorney      -->.<--Put complaints in this box
jshorney (at) inebraska.com
nu0c (at) amsat.org
Ham Radio NU0C
Lincoln, NE, USA
EN10ps
http://incolor.inetnebr.com/jshorney/

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