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Old 4th February 2004, 01:42 PM   #1
sobazz is offline sobazz  Denmark
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Question Measurement mic confusion...

Okay... I now have a preamp and a housing. I've bought the electret capsules too. But I not quite sure how to modify the capsule and hook it up...

Linkwitz (here) suggest to different configurations. What is the difference? Which one is the best to use with the ESP mic preamp (here)?

And how would you connect the 3-wire version to Rod's preamp?


Any help is greatly appreciated!



Regards
Soeren
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Old 4th February 2004, 02:18 PM   #2
sobazz is offline sobazz  Denmark
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I suppose I'll need to bypass R2 (in Rod's schematic) or actually remove it, and connect microphone terminal 1 to VE+, mic terminal 2 to Mic+ and mic terminal 3 to Mic-. But do I need the 4.7k resistor Rod shows in Fig. 8?
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Old 6th February 2004, 03:41 PM   #3
w00t is offline w00t  Singapore
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You shouldnt remove/bypass the 10K resistor between +VE and the mic's +ve terminal because it is present in Linkwitz's c) connection too.

just my 2cents.
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Old 6th February 2004, 05:48 PM   #4
sobazz is offline sobazz  Denmark
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No. In the three-wire (source resistor) wiring example, mic terminal 1 is connected directly to the positive terminal of the battery.

I tried out both. The source resistor mod did not give the result I expected. In fact, the SPL handling was still very limited (not like without the mod, though). The 2-wire version is way better, at it seems that Linkwitz prefers that one too. He doesn't mention the source resistor mod in the description.

The source resistor mod is also a pain to do. I destroyed two capsules trying to solder a wire to the case terminal. I cannot recommend it. The two wire mod is actually quite easy.

It seems, however, that I need a preamp. The mic input of my Audigy is rather crappy. The jack socket is supposed to be wired like this: ground-5v-signal (sleeve-ring-tip). Using a mono jack connecter should give you nothing but ground and signal... I got ground and 1.8v/signal.... I measured the mic input to be actually ground-3.2v-1.8v/signal.... probably the last time I buy Creative stuff

Does anyone know the output capability (voltage/current) of the ESP P93 preamp?. If possible I would like to have a gain of atleast 20db while maintaining frequency response.
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Old 6th February 2004, 09:54 PM   #5
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Hi Sobazz,

Which audigy do you have? I know the first one had quite a few problems, I've got the Audigy II ZS which seems pretty good. I just measured my mic socket and it's got gnd gnd, 4.96, 1.82V.... But it seems to work fine with the mic..... Hmmmmm I just measured the voltages with the mic attached, and I've got the 4.96V line not connected at all, and -.11 v on the signal line, something's funny with that, I thought I had the line with power connected. Now I'm wondering why it works at all..... I think I'll just make my preamp, now I've got all the parts

edit: OK I've just thought about it some more. The mic needs a certain amount of voltage to function, some mics (like the panasonic) only have two wires signal and ground, so in order to provide voltage to make the mic work you have to provide it on the signal line hence the 1.82V (this is DC). The signal from the mic will be AC, so they just use a cap between the signal line and the amp section of the SC's mic preamp, block out the dc and get the ac signal. Sound reasonable?

I guess the reason for the 4.96V (in my case) on the other line, is for mics that are wired for a separate power supply, advantage being (I imagine) higher SPL handling due to the higher voltage enabling bigger peak to peak swings in the output voltage before clipping.

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Old 6th February 2004, 10:07 PM   #6
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Quote:
Originally posted by sobazz

The source resistor mod is also a pain to do. I destroyed two capsules trying to solder a wire to the case terminal. I cannot recommend it. The two wire mod is actually quite easy.
Hi,

Use conductive glue for it !!! Best is to use a piece of brass tubing (1/4 or 6 mm inner diam) and glue the capsule inside the tube with a small drop of conductive glue. But be careful not to short the other connections with excessive glue.

I used a 4k7 source resistor and that works fine.

Cheers
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