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Re: Finding Shure 183

Subject: Re: Finding Shure 183
From: Dan Dugan <>
Date: Mon, 14 Feb 2005 21:41:55 -0800
>  >>>Could you comment on the impedance, I'm sure you understand it better
>>>>than I. The MX183 has a impedance of 150 ohms,
>  >
>>  Transformer output
>
>Presumably to match pro equipment better and handle longer cable runs?

Precisely. Though I put my rear 183s through a 40-foot cable and they
sound fine, someday when I measure it I wouldn't be surprised if
there's some roll-off.

>  >>>the WL183 is spec'd at
>>>>1000 ohms.
>  >
>>  Direct FET output.
>
>Intended for short runs to higher impedance mic pre's?

Exactly.

>  >>>I'm pretty sure my Portadisc is going to find the MX183 a
>>>>better match, as it's designed for low impedance mics like the MKH.
>  >
>>  I think the operative factor is the input impedance of the recorder's
>  > mic input. If it's high enough to "bridge" the mic's source
>>  impedance, it won't lose level by loading it down. "Bridging" means a
>>  load 5 to ten times the source impedance.  For a 1K source, that
>>  would be 5 to 10K.
>>
>>  Unfortunately, manufacturers usually don't tell you what the actual
>>  load impedance of a mic input is; they'll rate it with the mic
>>  impedance that it's designed to bridge, like a standard 150 ohms. 3K
>>  is a typical mic preamp input impedance. Higher is better, but it's
>>  hard to keep the noise down was the impedance rises, so it's a
>>  trade-off.
>
>So, one could say at typical preamp input impedance the WL183 is
>probably not meeting the 5 to 10 times rule for the source? But the
>MX183 would meet that rule?

Yes, but at the cost of a loss in level. Only experiment will tell
which is better.

-Dan Dugan


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