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Author Topic: Altec M20 Mic System Modification  (Read 1553 times)

LouD.

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Altec M20 Mic System Modification
« on: January 17, 2007, 04:23:34 pm »

Hello Everyone.

I am the proud new papa of an Altec M20 system, as well as a 195a mic with a 29b capsule. I understand that the 165a can be made to work with the cardioid capsule with the installation of one resistor.

If anyone is familiar with this conversion, I'd love some help doing this, as I am not so experienced.

As far as I can tell from the M20 and M30 schematics, it seems that there is a 22K resistor between pins 4 and 6 on the M30 - is this right?  (schematics attached)

I've been told that the resistor should be added inside the canon connector on the microphone side.  Would this be essentially the same as putting it on the 525 power supply side?  The reason I ask is because I would like the option of using the 21b omni capsule as well as the cardioid 29b capsule which requires the mod.  If the modification would allow for only the 29b capsule to be used, then I'd like to perhaps install the resistor on a switch, thus giving me the option.

If the 21b capsule could be used regardless of the resistor being in place, then I suppose it doesn't matter where I install the resistor.

Thanks for any help,

Louindex.php/fa/4065/0/
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Lou DeRose
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LouD.

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Re: Altec M20 Mic System Modification
« Reply #1 on: January 19, 2007, 01:24:56 pm »

Just added the schematic.  I had posted it in the mic lab forum, and they sent me here - forgot to re-load the jpeg.  

Anyways, thanks for any help..
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Lou DeRose
Independent Music Maker
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