do you think it is ok to remove the transistor?
Because i forgot to mention that between the op amp and the transistor circuit i use a stereo cable about 1m long

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If the 100k trimpot is set to about 105k (plus and minus depending on the gain of the transistor) then the circuit will be very sensitive. But since the transistor does not have any DC negative feedback then it is also sensitive to temperature changes.
The transistor will also amplify changes in the supply voltage.

I was taught that such a simple transistor circuit should never be used for anything.

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Uncle $crooge

 

Thanks again for replaying Audioguru,

I've change the pot with one of 10k + ore 10k resistor in parallel(i don't have a 5k right now) and the result was almost the same in sensitivity..so i change the 2n2222 with a bc547 (measured gain is 650) and the sensitivity has increase a little bit. Maybe the mic is not sensitive enough - i think is a Velleman with a sensitivity around -68dB and a nominal voltage of 4.5V - next week i will receive a new mic BCM-9767P from BE-STAR -44±2dB (VS=3V/RL=2,2kΩ) i hope that will do the job.

Do you think is a good idea to remove the transistor near the mic as i connect the mic preamp with lmv722 input with a stereo shielded cable about 1m long?

 

You need to learn about transistors to see that yours were designed completely wrong.

If you bias the opamp properly and use negative feedback then it should work fine without a transistor. But that opamp has a much lower max gain than normal opamps.

I don't know if the very short sound duration is enough to trigger your camera.

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Uncle $crooge

 

How about this one?

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It is good that the first transistor has a bypassed emitter resistor for good DC stability.
The second transistor is not needed.
Maybe an adjustment should be available to set the sensitivity.

Please connect a resistor in series with the base of the 3rd transistor to limit its base current.

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Uncle $crooge

 

sorry,
I'm a little bit confused... Correct me if I'm wrong

1. Replace R3 10k with a pot (i think same value...maybe 15k)
2. I have to connect a resistor at the base of Q2 (because i only have 2 transistors in the circuit) but if i put a 1k resistor the amplification after Q2 will be smaller than the on give by Q1 - i didn't simulate the circuit but i think that the Vout from Q2 is smaller with at least 0.7V

 

I don't know why you are using a preamp with two transistors when only one properly biased transistor is needed.

If the preamp works then don't change its parts, instead make the R8/R9 voltage divider adjustable for sensitivity.

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Uncle $crooge

 

Thanks,
I will try that and let you know the result.

I know that i'm annoying with my questions, but this is by far the most complicated project that i made so far. I tray to learn by myself but some times i get no results...and i become annoying.
Thanks again.