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Re: Low frequency hum with musical accompanyment

Subject: Re: Low frequency hum with musical accompanyment
From: Dan Dugan <>
Date: Mon, 17 Mar 2003 16:30:40 -0800
>  > Open the male xlr plug and make sure the shield is going to both pins
>>  1 and 3, and the hot to pin 2.
>>
>
>This should not be necessary. I, in fact, don't tie signal cold to
>shield on purpose. So if you forget and leave the phantom power on you
>won't short it out. And I never have these problems. I did not even when
>I was still using the Telinga with the Stereo miniplug cable.

We're talking about an unbalanced microphone circuit coming in that 
has just hot and shield, and how to connect it to a 3-pin XLR input.

If the input is transformer isolated, as the best equipment is, the 
result of leaving one signal pin (2 or 3) unconnected will be low 
gain, increased noise, and a scratchy, treble-emphasized sound.

If the input is electronically balanced, as in mid-priced gear, the 
result will be increased noise from the unterminated leg.

Of course it's necessary to keep phantom power off when using an 
unbalanced mike. That's why it has a switch.

Walt, if you've been able to get away with wiring your mike inputs 
wrong, you are either 1) not getting the best performance from your 
gear, or 2) very lucky.

>The problem is almost certainly in the ministereo jack end. Poor contact
>between it and the plug.

Unquestionably, any mini-stereo connection is always a prime suspect. 
Use Caig Laboratories contact lubes, replace female connectors when 
they get flakey.

-Dan Dugan


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