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Forums :: Ask Harp Mic Expert Greg Heumann

cabling question

2 replies [Last post]
Tue, 01/31/2017 - 00:08
bod
bod's picture
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Level 5
Joined: 06/19/2016

Hello Greg Heumann

I bought a Shure CM cell from the 60's. I did put a good mic cable (2 wires and a shield).

 

I did cable it with a jack, soldering together the shield and one of the wires to the larger part of the jack. It does work well.

Nevertheless there is a lot of (white) noise on the recorder side (zoom H5) if I turn the input gain knob in its middle position.

 

I don't know if the noise comes from the cell or from the cable.

What can I do to reduce the noise ?

Should I change my cabling to an XLR socket to dissociate the shield and the signal wire ?

If I do so, I can still connect to my recorder, but it will be harder to connect to an amp, won't it ? (I don't own an amp yet).

 

Thank you for your answer.

Bod

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Tue, 01/31/2017 - 08:46
#1
Greg Heumann
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Expert
Joined: 04/29/2010
Hi, Bod  Because the element

Hi, Bod

 Because the element and the cable are both passive devices, they cannot produce any white noise. The only time any current passes through the cable is when the element is converting sound waves into electrical signals. 

Your white noise probably has more to do with the Zoom's interface. Are you sure it is high impedance? Also - many recorders have an automatic gain control ("AGC") which increases the record level higher and higher in the absence of any input - then when there IS input it adjusts automatically. The result is that, in the absence of something to record, the background noise gets amplified. I hate AGC!If the Zoom has a stereo 1/4" or 1/8" input, or XLR, the odds are very good that it should be wired in "balanced" mode - in that case the shield is ground only  and not part of the signal path. The signal should be placed on the two center wires. Whether or not you need an impedance matching transformer is unknown, but that will be far less important than resolving whether it wants balanced or unbalanced input. 

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Sat, 03/04/2017 - 08:10
#2
bod
bod's picture
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Level 5
Joined: 06/19/2016
Thank you

A little thank you note for the time you took to answer.

I found this in an album. Thought you might like it (see the second image below).

 

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