Any simple mods for lowering the noise floor of microphones?

...and how to do so...
jp008
KVRist
44 posts since 15 Oct, 2010

Post Tue Nov 05, 2019 2:23 am

So I bought a pile of cheap microphones to have some fun with.. a couple of dynamics, a condenser and some type of crazy karaoke mic. Upon plugging them into my preamp, I jacked up the gain and you know the rest. Mmmmm.. delicious white noise.

Then I got to thinking again (dangerous in my case, believe it), WHAT IF instead of expecting a bunch of white noise when cranking up the gain on my preamp, I just solder a bunch of stuff between the mic capsule and the XLR output to see if I can lower the noise floor BEFORE plugging it into the preamp. Eureka !

Then I did and internet search and.. nothing. Amazing ! I think I found a diamond in the rough thinking of microphone designers throughout the ages.

That said, please post any possible simple 'noise floor lowering' microphone modifications ideas you might have, so I can keep myself busy. Thank you. :party:

Again, it doesn't have to be elaborate, just some simple stuff to try with 3 or 4 components. It's not like I could fit a big fancy circuit board into a microphone anyways. Duh?

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Tj Shredder
KVRAF
3380 posts since 6 Jan, 2017 from Outer Space

Re: Any simple mods for lowering the noise floor of microphones?

Post Tue Nov 19, 2019 12:59 am

The reason why they are cheap...
The only way is software, spectral noise reduction. Most likely the capsule itself is noisy, whatever you place between would rather create additional noise...
But aside, check impedances, if they are not matched between mic and preamp you get more noise...

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DJ Warmonger
KVRAF
3457 posts since 7 Jun, 2012 from Warsaw

Re: Any simple mods for lowering the noise floor of microphones?

Post Tue Nov 19, 2019 1:02 am

I just solder a bunch of stuff between the mic capsule and the XLR output to see if I can lower the noise floor BEFORE plugging it into the preamp. Eureka !
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whyterabbyt
Beware the Quoth
27705 posts since 4 Sep, 2001 from R'lyeh Oceanic Amusement Park and Funfair

Re: Any simple mods for lowering the noise floor of microphones?

Post Tue Nov 19, 2019 2:33 am

jp008 wrote:
Tue Nov 05, 2019 2:23 am
So I bought a pile of cheap microphones to have some fun with.. a couple of dynamics, a condenser and some type of crazy karaoke mic. Upon plugging them into my preamp, I jacked up the gain and you know the rest. Mmmmm.. delicious white noise.

Then I got to thinking again (dangerous in my case, believe it), WHAT IF instead of expecting a bunch of white noise when cranking up the gain on my preamp, I just solder a bunch of stuff between the mic capsule and the XLR output to see if I can lower the noise floor BEFORE plugging it into the preamp. Eureka !

Then I did and internet search and.. nothing. Amazing ! I think I found a diamond in the rough thinking of microphone designers throughout the ages.

That said, please post any possible simple 'noise floor lowering' microphone modifications ideas you might have, so I can keep myself busy. Thank you. :party:

Again, it doesn't have to be elaborate, just some simple stuff to try with 3 or 4 components. It's not like I could fit a big fancy circuit board into a microphone anyways. Duh?
If 3 or 4 components could make any significant difference to lowering the noise floor of a cheapo microphone, those 3 or 4 components would be built into cheapo microphones as standard.
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aciddose
KVRAF
12312 posts since 7 Dec, 2004

Re: Any simple mods for lowering the noise floor of microphones?

Post Tue Nov 19, 2019 2:46 am

There are actually several ways you can easily beat the preamp's noise performance by using buffers or amplifiers at the source rather than at the destination. This is why active mics already have such a buffer/amp built in.

One method that works quite well is if you're able to trade distortion for noise... for example you might introduce harmonics like 2nd -30, 3rd -20 or similar. This is a fairly nasty level of distortion, but by using a non-linear amplifier with much higher gain ("soft clipping") you can dramatically increase your headroom and reduce overall noise by amplifying the signal from the mic before the noise is introduced.

There are a number of different buffering strategies that work best depending upon your exact aims... but generally speaking if you're using a good active mic it's already using the best possible method to minimize noise and maximize linearity (minimize THD.) So if that's your aim (the most common aim), you're best to use quality equipment designed for that purpose.

The only time you're going to do any better is as I mentioned in a situation where you're trading noise vs. distortion vs. bandwidth, and only because you're making some sacrifice that the designers aiming to satisfy the common demand were unable or unwilling to make.

Sometimes a mic with a "poor" THD is absolutely great.

Try follower -> common base amplifier -> follower (3 transistors, 3 resistors, 2 capacitors). This will be highly non-linear but provide great gain with minimal noise. If you don't want non-linear you need either a more complicated amp or you're stuck with a simple single stage buffer. If bandwidth and input impedance are an issue, the solution is generally a NJFET buffer rather than a BJT transistor... but then you have the issue of VGS variation.
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