Simplest possible mic preamp

Given a system that has 4-5VDC on the microphone line, I've made a preamp from three components that amplifies a signal from about 10mV to over 2v. Surely there is distortion, but it's a motorcycle intercom and intelligible speech with a reasonable amount of fidelity is fine.

My question is this: Even one or two other components would be ok if they improved it.

The basic circuit is a common emitter BC548 or similar, a feedback resistor (1M) from collector the base, and the mic feeds base and common, and the output is collector-emitter. The mic lines have DC voltage to power the preamp, and the transistor simply puts an analogous AC signal on top of the DC power.

I had some base-common and collector-base 1pF caps on there to stabilize it, but the ckt performs the same with or without as far as I can tell.

Suggestions? I'll post a 5Spice diagram if anyone is interested.

Ed

Please define "improve".

Lower distortion? More gain? Adjustable gain? More stable? Tailored frequency response? Noise/wind rejection?

More gain would help. I have 200-Ohm mics that give higher output and trigger VOX systems easier, but they sound lousy, and 600-Ohm mics that are excellent in quality, but it is harder to trigger VOX with them, so higher gain would be good. I considered a second stage, but the goal is 'simple as possible'. Adjustable gain is easy enough to get (variable resistor on emitter) but in practice it would be hard to have that and be water resistant too. Besides, I think this is about all you can expect from a single stage. Changing the C-B feedback resistor really doesn't have much effect on gain as far as I can tell. Different transistors (garden variety NPNs) don't seem to make a difference either.

I think higher gain is the definition of 'improve' in this case.

You mentioned noise/wind rejection. How would you achieve that other than mechanical means? I find that filters take out as much voice as wind since they are very similar in frequency when I've done FFT analysis on the separate and combined signals. There are excellent active systems on the market now that I could integrate, but the cost is prohibitive since it requires a processor and power and case, etc.