help! in need 10 watts (or more) audio amplifier schematic transistor based

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What we were trained to do was to put 10 ohm or 22ohm resistors in the supply rails (often in place of the fuses), then if the amp had a fault or severe bias arror etc a resistor would start to cook and make a bit of smoke, but no transistors would be killed.

Once the amp had been tested with a sinewave and no load (or a light load) the resistors would be replaced with fuses and a proper load connected. Often smaller fuses for the first tests!

If people in your school are destroying FETs all the time the teacher might need to suggest a better methodology.
 


Thank you very much for the links . I found one schem which used an all BJT transistor. I think I'll try that one up. Hope all the parts are available in our stores. (45 watts class B Amplifier)

By the way, its okay to supply the circuit with a (33+ and 33- Volts and 3 A) transformer or (30+ and 30- volts, 1 A) transformer right? it wouldn't fry up or anything.... Sorry, I really just want to make sure to lessen expenses and all and deadline is quite near.
 
A 45W audio amplifier has an output of 45W and produces heating of about 35W. Then a total of 80W is used from the power supply.

The project uses a 25V-0V-25V transformer to make plus and minus 33V. The maximum current drawn by one amplifier at its maximum output power is 80W/66V= 1.2A.

If you use a plus and minus 30V power supply then the maximum output power will be reduced to about 36W and the max heating will be about 28W for a total of 64W. Then the maximum current drawn by one amplifier at its maximum output power is 64W/60V= 1.1A.

Of course something will fry if you connect something wrong. But that amplifier circuit uses Q8 and Q9 to limit the maximum current.
 
Good news everyone the original circuit that I made already worked. Thank you very much for all your help! I will still make the 45 W class B amplifier for my personal use ... I find making amplifiers really interesting now .

The problem laid under the following:
1. wrong positioning of our BC547 transistor.
2. short circuit between heatsinks (took a very long time to see that)

Though there is still a problem with one of our mono amplifier (I made 2 for stereo) which doesn't produce a very smooth sound like the other one. Perhaps this has to do with a defective capacitor?
 
Cluene said:
...
The problem laid under the following:
1. wrong positioning of our BC547 transistor.
2. short circuit between heatsinks (took a very long time to see that)
...
Click to expand...

Both are common problems on a hobby amp build, congrats on finding the faults and getting the amp working.

And as I said before, if you had put 10 ohm resistors in the fuse holders you could have caught both those faults with no damaged parts (except maybe the 5 cent resistors).
 
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