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Good Day Microphone Fans.

I have a pair of very low cost little circuit boards for condenser capsules. I purchased them in the spirit of DIY experimentation, notwithstanding I cannot find any information about them. Can anyone tell me anything helpful about either of the boards shown in the attached images? I prefer not to guess what sort of capsule matches each of them, respectively. I do not mind experimenting, but loathe the prospect of roaching them or any capsules by letting the all-important essential smoke out by inappropriate pairing.

Thanks loads. James

Hi James

It's possible to search for images at
Just click the little camera symbol in the search window to upload an image
I uploaded one of your images. Here you will find? .

Hope this helps!

Heinz

Hi James,

The second board with the 3-pin plug is for connecting an electret without built-in FET to a phantom powered XLR mic input. It has the K596 FET on board next to the mic input pads. Read more about that circuit here:

and any / all of the posts about BM800 mics. This is the Generic China Mic circuit. A lot of these pencil mic boards barely work because the circuit was copied wrong. Let us know how yours turns out. I haven't tested any of the red ones.

I'm guessing about the smaller board, but it looks like it's made to hook an electret capsule with built-in FET to a 5V power supply and A/D converter, for instance to hook a small electret capsule to an analog input on a Raspberry Pi computer. The large chip looks like a "117" linear voltage regulator and the small "ABK" chip looks like a mic preamp. Look for info among the tiny computer fan websites.

Have fun experimenting!
Henry

THANK YOU @Henry Spragens !

This is exactly what I am looking for, and your reply mirrors my own best guess. I just did not want to hook things up without asking first - experimentation should be a directed, and not a hit and miss, enterprise. :-)

Thank you for the link to you work with the similar, brown-colored boards. I have used several of those with pleasing results. I use several microphones using them with amateur radio transceivers and computer speech recognition applications. While I cannot say they are studio quality, they are sufficiently quiet and clear for my use. I attach photos of one such home-brewed project that turned out well using a hacksaw, drill, and short length of scrap aluminum antenna tubing.

I appreciate the heads up and will proceed accordingly. Thanks for the confirming uptake. James / K8JHR

@ James,

So you have used some of these Chinese mic boards successfully. I’m curious whether yours have missing bass like the ones I’ve seen. For radio or speech recognition, that might be a good thing, actually.

The green boards inside these lollipop mics work OK after adding a filter cap (blue electrolytic in photos), but output polarity is wrong for studio use, requiring trace cuts and jumpers to swap pins 2 & 3. These boards don’t have the phase inverter problem.

re:
"The green boards inside these lollipop mics work OK after adding a filter cap (blue electrolytic in photos), but output polarity is wrong for studio use, requiring trace cuts and jumpers to swap pins 2 & 3. These boards don’t have the phase inverter problem.
"

I got to wondering if these green PCBs from 10 years ago DO have the "inverted inverter" transistor after looking at the frequency response charts. Turns out they do. The PNP transistor used works better reverse biased than most, so bass rolloff isn't as severe as the black boards. There is a little more room around the transistor in question, so it is possible to leave the base soldered to the board, unsolder the emitter and collector, stand the transistor with collector upward, swing the emitter over and tack it to the proper pad, then run a wire from the collector to the proper part of the circuit. Looks something like this:



There are a couple of other mistakes in this PCB, so this may be where the swapped E & C connections in Asian pencil mic boards came in.