negrinflon
4 posts
Apr 14, 2014
3:11 AM
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Hi
1.5" Dia Mic insert Dual Imp 20K & 300 Ohms Racal Acoustics.
Soldered it up to 1/4 inch jack. Pushed Bass guitar cable lead into socket and linked up to Pignose.
Switched on...nothing..tapped Racal ...nothing
Why can I not build my own microphone when everybody else can
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5F6H
1760 posts
Apr 14, 2014
5:34 AM
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Maybe the element is dead?
Maybe you have more than 2 terminals on the mic element and/or 1/4" socket?
I have a 1/4" plug, with 2 wires terminating in 2 insulated crocodile clips, I use this for testing mic elements & speakers.
Got pics?
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negrinflon
5 posts
Apr 14, 2014
6:16 AM
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Hi
The mic Element should be Ok
There are 4 terminals on the element 2 for 300 ohms and 2 for 20K
How do you test the elements
Thanks
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5F6H
1761 posts
Apr 14, 2014
8:05 AM
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I had a look at a recent e-bay auction for something similar to what you describe - how are you determining which terminals do what?
I test them with said lead, clip it up, plug into an amp and bark into element until I can hear the amp barking back...maybe play a little harp if a good hand hold...but man, I love barking.
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negrinflon
6 posts
Apr 14, 2014
9:14 AM
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According to the guy who sold me the Racal the two tags on either side of the word RACAL are the 300ohm ones
The other two are the 20K ones
I have linked it up with clips but no response
Wondering if anything is wrong with the lead to the amp
Have a Shure Prologue 10H and this works perfectly
Just a handy sort of guy so I want to roll my own!!
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5F6H
1764 posts
Apr 15, 2014
4:24 AM
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Do you have an AC voltmeter (RMS preferably) with crocodile clips/wire grabbers? Clip the common lead to one terminal, then the red lead to all the others in turn (you can shunt the terminals/clips with a 1 to 5meg resistor if you like), play into the element, keeping it cupped, what voltages do you get?
Rotate the common lead around the different terminals & repeat until you see a volt or two?
If you get no signal at all (could just be a few 10's of mV in lo-z), from any of the combinations the element is a dud.
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Last Edited by 5F6H on Apr 15, 2014 4:26 AM
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negrinflon
7 posts
Apr 15, 2014
9:27 AM
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SOLVED The Problem
Thanks guys for help. Will print off the advice re Voltmeter.
Problem lies in the cable from amp to microphone.
This has a jack at the Pignose and a jack to the mic socket.
Got an xlr socket to replace the jack one and another mic insert. Wired the xlr up 1 1nd 3 linked. 3 negative 2 positive. Worked perfectly with the xlr to jack that I use for a Shure prologic.
So must be the cable Stagg.
Problem in my mind still is this. The jack socket and do you need to earth it?
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5F6H
1766 posts
Apr 15, 2014
12:02 PM
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The common mic terminal is wired to the sleeve terminal on the jack socket. This is then typically grounded to the amp's circuit ground via the cable's shield/drain wire.
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