Back of board - it appears there may be a short on the board between row 5-6, and near the middle row 12-13.

That did it! There was a TINY bit of solder splatter (don't ask) that was shorting between pins 2 and 3 on the IC (which are input + and -). I now get sound!...

...but it's very quiet. In fact, it's hardly doing any amplification at all so something else is clearly amiss too. Maybe I've simply wired my VR up wrong... (even without it wired up at all, it's still quiet though).

I'm going to test my values against kubeek's diagram, and see if I can narrow down the problem.

This is how in theory the DC voltages in the circuit should be, plus minus some component variation. Check if your values are the same.
edit: attachment

Will check these. Thanks.


I might just build it again. I bought enough components for about 8 I think. Also, yesterday I made a prototype PCB in Fritzing (which is AMAZING!), and could get two printed for £5 posted, which would save messing around with stripboard.

I've checked it over a couple of times, and it seems quite good to me, and the software confirms that all connections are made properly etc. It's my first PCB attempt though, so a lot of things could probably be done a LOT better.

 

IT LIVES!

Here's a sound sample... the mic is currently running off only 17v, when it needs 22v, but it sounds fantastic regardless. Will be buying a battery now I know it works!

https://www.dropbox.com/s/l3njfjg1aauiv04/mic_preamp_test.mp3

Thanks so much for all of the help, everyone! I wouldn't have been able to do it without your suggestions and guidance!


In total, the whole setup, including the microphone and PCB but excluding the recorder, cost £50. My mind is blown!