Craig Anderton's practice amp problem

[Aharon]

I built Craig's LM383 amp,fairly easy build thanks to Dean's PCB,tried it and it works fine with one glitch.....if you really hit the low strings hard it farts out.
I used 12VAC at 800mA to power it,maybe I need more like 18V.
Also.... it's nowhere near 7W,more like 1/2W.
Anybody built one and found the same thing?.
Thanks
Aharon

[Mark Hammer]

1) Is 12V at 800ma enough?

2) Is the speaker the appropriate impedance? (and is the speaker in decent shape?)

3) The gain is set by the feedback and ground resistors, much like an op-amp.  Verify it is set for the sort of gain that will get you what you expect to hear/see.

4) How hot is it and do you have any heatsiking?

[calpolyengineer]

I just checked the data sheet and the 7W output is with a 2 ohm load. Also the supply voltage is from 5 to 20V.

Now correct me if I'm wrong, but you wrote that you were using 12V AC, but wouldn't it need a DC supply? If so, I could see how that would cause your problems.

-Joe