amplifier circuit(2N3904) giving no sound

[rahulb]

Hi Everyone,

I am a beginner hobbyist.

I made a ding dong bell circuit, you can see it below

but, sound at output was too low. I am using a 8 ohm speaker, may be 3 or 5 watt.

so, I added a dual 2N3904 circuit for amplification of sound, you can see the circuit below:

but there is no sound at output. I calculated the timer 555 circuit's frequency, it is coming around 700 Hz.

what I am doing wrong?

please help me.

thanks

 

[Alec_t]

Welcome to EP!
Your amplifier is really only a 'pre-amplifier' and is fine for small signals but can't provide enough current to drive an 8Ω speaker. You need a power amplifier. Google should find you many circuits to try.

 

[Harald Kapp]

This circuit is a high voltage gain amplifier, but has a high output impedance. It is completely unsuitable to drive a speaker. You don't need voltage gain as the 555 outputs a high amplitude signal. You need current gain to drive a (comparatively) low impedance speaker.
A rather simple design is e.g. here.