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Expert analysis welcomed on my Audio amplifier circuit

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Well,we all make mistakes from time to time,don't we?I certainly do.
My humble recommendation is to remove those two components(or at least change to 1n).Thereby the tone control should work as a unity gain stage.Remember that this unity gain is with all tone controls in the middle,so advancing one of them increases the gain up to maybe +15dB.
There's still a lot to be said about this circuit,but nevertheless it should work.
 
I still have a breadboard prototype so I will tinker with the circuit. You guys have been a tremendous help and I can use all of your information to help me fully understand the operation of the circuits.

Thank you all so much!!!

Audioguru, my next built will certainly be aiming for a more poweful and better performing circuit, so thank you for your tone control circuit, I will make use of it.

Thank you all so much!!!

EDIT: I made a mistake on my circuit diagram. The circuit and initial(penciled) diagram cap C6 is indeed 1nf.
 
Ok, Thanks for all your help, I got an A for my project and my class was impressed by my circuit. I am now going to make a far superior circuit using the SANYO LA4440 IC and implement Audioguru's Baxandall tone control circuit. THe OPA132 is way too expensive though, £17 each over here, so I will substitute for the OPA134.
 
Congrats to Norman on a successful project. Neither op amp was meant to be used at 9V, but the 741 is more likely to work. As for C6 and R8 they were meant to stabilize an amp that was not unity gain stable and can/should be removed. On the other hand hanging three pots onto the input of a fast op amp is likely to make it unstable so adding a small cap from out to minus in is a good idea. The tone control circuit is an old and much copied design that doesn't actually perform very well, the midrange control is the worst, but changing the bass alters the treble. Several years ago I created a version that improved the action of the midrange and reduced the interaction between the three controls. I have always thought I should do a write up to publish somewhere but have never gotten around to it.
 
Hi,

Yes i agree that 9v is not enough voltage for many op amp types.

Norman if you want to use the LF type or any other type with FET inputs then try using TWO 9v batteries to give you plus and minus 9 volts or even just 18v to start with. The op amp inputs dont work very well with a lower voltage.
Be aware though that the little 9v batteries wont last all that long running this thing.

They make some fairly nice op amps for low noise audio work, but the LM386 chip will just add more noise anyway.

To find out if your circuit is working properly for audio, you would want to connect a distortion analyzer to the output and use a signal generator on the input that generates a clean sine wave. If you cant get a distortion meter then you can input a sine wave and look at the output of the op amp and the output of the LM386 and compare it to the input wave on a scope. It's not easy to see low distortion but you'll notice the distortion if it is high enough.

Also, high capacitance across the power supply is a good idea to handle higher amplitude signals. At least 1000uf or better.
 
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