Building a 15 W audio amp

[sirmarcou]

Hello everybody,
I'm building an 15W audio amp and I found a usefull schematic for one:
https://www.eleccircuit.com/wp-cont...-audio-amplifier-15W-by-NE5532-transistor.jpg
Now when I was examining the circuit I discovered that the opamp used is the 2N3055, but this is a transistor, and not an opamp?
In the title you can see 'NE5532', but not in the schematic, this makes me confused...
Can someone help me out?

 

[crutschow]

Yes, the op amp should apparently be an NE5532.

But the circuit won't work as shown. The collector of Q1 is connected directly to the -18V so it can not drive Q4. There should be a resistor in the Q4 collector.

And even if you get it to work it will have high crossover distortion since the output transistors have no bias. All-in-all it looks like a poor paper design that no one has ever built.

If you want to built an amp then use one the audio power ICs designed for that purpose. They are easier to use and work much better.

 

[audioguru]

It is almost the worst amplifier design that I have ever seen!
The first stereo receiver I ever bought was made by HH Scott in 1964. It uses old 2N3055 output transistors but doesn't have the problems with this horrible circuit.

 

[Mr RB]

Surely that circuit is a joke? It doesn't even have the DC decouple cap on the speaker!

Maybe the bottom of the speaker is supposed to connect to GND not -18v?

 

[Nigel Goodwin]

I would agree, it's missing most of it's components, and couldn't possibly work - plus it would destroy the speaker as it's connected wrongly (no speaker coupling cap required in a spilt-supply amp, but the speaker should go to ground).