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Why won't my mic preamp work on my condenser mic ?

Member for

14 years 9 months
I have an MXL990 mic and I run it through the same stereo microphone preamp that works for my stereo Sony electet mic. Is it because my mic is mono and I need to get the right fittings to go into my stetro preamp ? ...or is it because of my preamp specs ? It was made by a guy that builds them and sells them on eBay: Church Audio ST-20. Here are the specs for the 9-volt driven preamp:

SELF NOISE BELOW -120DB S/N RATIO WITH NO INPUT CONNECTED

NEW THD+N 0.029% -70 AT -20db

NEW THD 0.010% -79 AT -20 db

NEW FREQUENCY RESPONSE FLAT FROM 20 HZ TO 90 Khz +- .5 DB

NEW GAIN RANGE FROM -27 TO +30 IDEAL FOR MAKING THE MOST OF YOUR SIGNAL TO NOISE RATIO AND FOR ACTING AS A PAD IN LOUD SITUATIONS LIKE CONCERT RECORDING

PROVIDES A FULL 9 VOLTS PLUG IN POWER FOR ALL STEREO MICS THAT REQUIRE IT

Thanks

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Member for

15 years 7 months

TVPostSound Fri, 12/08/2006 - 20:13
bahed wrote: I have an MXL990 mic and I run it through the same stereo microphone preamp that works for my stereo Sony electet mic. Is it because my mic is mono and I need to get the right fittings to go into my stetro preamp ? ...or is it because of my preamp specs ? It was made by a guy that builds them and sells them on eBay: Church Audio ST-20. Here are the specs for the 9-volt driven preamp:

SELF NOISE BELOW -120DB S/N RATIO WITH NO INPUT CONNECTED

NEW THD+N 0.029% -70 AT -20db

NEW THD 0.010% -79 AT -20 db

NEW FREQUENCY RESPONSE FLAT FROM 20 HZ TO 90 Khz +- .5 DB

NEW GAIN RANGE FROM -27 TO +30 IDEAL FOR MAKING THE MOST OF YOUR SIGNAL TO NOISE RATIO AND FOR ACTING AS A PAD IN LOUD SITUATIONS LIKE CONCERT RECORDING

PROVIDES A FULL 9 VOLTS PLUG IN POWER FOR ALL STEREO MICS THAT REQUIRE IT

Thanks
You need 48V, not 9V

Member for

15 years 11 months

RemyRAD Fri, 12/08/2006 - 21:28
Yup and that's the rub. This is what we refer to as a " True Condenser Microphone". Which means unlike an "electret condenser" microphone, with their permanently polarized diaphragms, which needs very little power to make the FET impedance converter work, because it doesn't have to polarize the capsuleAnd so those are the ones that can usually accept a penlight battery or virtually any phantom voltage.

A true condenser microphone, like a Neumann U87 and yours, requires every bit of that 48 volts and as the specifications state plus or minus 4 volts, so either 44 or 52 but not 9 volts as so many other condenser microphones will accept, that are known as "Back Electret Condenser Microphone". Those of that type that can frequently accept a penlight 1 1/2 volt battery but not a True Condenser Microphone.

Now you might be wondering, which is a better? Well back in the day, only the True Condenser Microphone was the quality product. The back electret condenser microphone were known to be inferior by comparison. But engineering and manufacturing got better through the years. Companies like Shure Brothers introduced a really fine Back Electret Microphone back in 1978 that is still in production today known as the SM 81 and all of those tiny lavalier microphones you see on the newscasters are really lovely and very flat sounding back electret condenser microphones that cost a pretty penny. The SM 81, can work on almost any phantom voltage but being a professional studio product, it doesn't accept any batteries, unlike all of the lavalier microphones, which by the way, can make for some bitchin' drum microphones when mounted creatively since they are mostly omnidirectional except for the Sony ECM 66 which is a cardioid. Of course, the smaller the capsule, the flatter the response and the higher the noise but when you're dealing with drums, the noise isn't much of a factor.

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Ms. Remy Ann David
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