pil wrote:

that really helped alot. Pinouts of my transisors are correct because I
measured their HFE's on my DMM.

One question, about the mains hum - I am using a 1,5V cell. Will I still
hear the hum if I use this cell instead of using a mains PSU? And if so,
why?

I built that circuit, and played around with it trying to get the AVC to
work a bit better, but with little success. The bias on that stage is
very low, and may be part of the problem. As the input to the mic
changes, so does that bias, so it's difficult to tell what the votlage
should be. But with the input at minimum, the circuit should have
maximum gain.

Also, I used an earpiece out of a telephone handset instead of a
headphones. It's louder, and uses less battery current.

[snip]