mini camcorder audio hack

[R005T3r]

Hi,

I have a faulty microphone on a mini camcorder that needs to be replaced. When I used the camcorder I wasn't impressed with the audio quality of the thing, so I decided to desolder the mic and replace it with a better one. Space is not an issue, because I decided to put it outside the box (with a shielded coax cable)

Unfortunately there's one big problem: I have no idea what kind of microphone is, and then I don't have any experience on these type of hacking.  I know for certain that it has a 4 mm diameter. Images on the second post

What can I do to identify the microphone and hack it properly? Thanks.

[R005T3r]

[alanb]

it looks like an electret microphone.

[Richard Crowley]

There is a 99.9% chance that it is a common electret condenser microphone capsule.  In large quantities (as the manufacturer uses), they cost a fraction of 1€.  They are available in places where electronic components are sold, such as "input transducers" for the Arduino crowd, etc. 
 
I would prefer to replace the original mic capsule with a 3.5mm jack so that you could plug in common external mic products. That would be much more convenient than having a permanently-attached cable and kludged microphone.  And it would give you the flexibility of using different kinds of mics for different purposes. (Such as a clip-on lavalere or a "shotgun" directional mic on a boom, etc. etc.)

[R005T3r]

That's a fantastic idea!
But what can I do? I should simply solder the mono jack socket and then take a microphone and plug it on?
Can I use any kind of microphone or it must be the same type? Do I need to match something in the circuit?

Thanks

[Richard Crowley]

There is an excellent chance that you can simply wire the two connections to the tip and sleeve of a 3.5mm jack and any of the 3.5mm accessories will work.  No additional circuit components required. The electret condenser mic capsule requires low-voltage DC to power the internal FET transistor (impedance buffer). This is called "plug-in power" and is the common standard for all the 3.5mm connector products (including phones, etc.) 

However, note that phones that use TRRS connectors are not wired the same. 

[R005T3r]

Unfortunately I don't have any microphone, I only have a piezo disc...

[Audioguru]

An electret microphone gives good sound. It must be connected with the correct polarity, see the "mic+" and "mic-" on the pcb?. A piezo disc sounds awful as a microphone and a piezo disc can produce an output voltage high enough to destroy the circuit.

[Zero999]

Unfortunately I don't have any microphone, I only have a piezo disc...

That will not do. As mentioned above, a piezo disc will sound much worse than the original microphone.

Proper electrect microphones can be bought from many suppliers.

https://www.adafruit.com/product/1064
http://cpc.farnell.com/kingstate/kecg2742tbl-a/microphone-electret-condenser/dp/MP34514?CMP=CPC-PLA

[R005T3r]

Ok, I bought a electret microphone from the local seller, Installed and shielded, with a 3.5 jack plug. I got good results: noise is almost gone, and you can clearly hear the difference.
Now I've cooled down the CMOS sensor and the main BGA with an heatsink.

Doing the first tests today.
Also, soldering in a high density board without a microscope is very hard!