Electronics > Projects, Designs, and Technical Stuff

Universal LM386 Audio Box

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jonovid:
here is a little box for the bench
its a universal audio amp.
if you do anything with analog audio, generally you will need a way of testing things.
this little box is made from an old Dick Smith intercom.
and has a DIN port for adding what ever! even if its just to use the 6 volt pin.

floobydust:
Just a note, I was revamping an LM386 signal tracer I'd made a long time ago.
It's like your circuit but the input has a blocking capacitor with diode clamp, and a 1MEG pot. I add a 1000pF cap from pin 3 to GND to stop AM radio pickup. For headphones, I add an extra 100R resistor so my ears don't get blasted.

If sound quality is poor, dirty or gritty sounding - as always, the LM386 does like to burst oscillate around 13MHz. The output network 10R 0.1uF helps somewhat but the only fix I find is 2.2uF X7R ceramic cap right across Vcc and GND at pins 4,6. Without these, I've never had the LM386 behave itself.

jonovid:

--- Quote from: floobydust on October 05, 2019, 01:12:46 am ---Just a note, I was revamping an LM386 signal tracer I'd made a long time ago.
It's like your circuit but the input has a blocking capacitor with diode clamp, and a 1MEG pot. I add a 1000pF cap from pin 3 to GND to stop AM radio pickup. For headphones, I add an extra 100R resistor so my ears don't get blasted.

If sound quality is poor, dirty or gritty sounding - as always, the LM386 does like to burst oscillate around 13MHz. The output network 10R 0.1uF helps somewhat but the only fix I find is 2.2uF X7R ceramic cap right across Vcc and GND at pins 4,6. Without these, I've never had the LM386 behave itself.

--- End quote ---
  I know about the AM radio pickup problem. yes you are right, some fix's are needed, the circuit has a little too much gain.  the odd switching is because had no space for a multi pole switch in the box,    My intention is to use this, to test circuit bending & analog music synthesizer circuits.

001:
Do You really use it with microphone?

floobydust:
I have an electret condensor mic input (no dynamic mic), not for yelling at people but to quickly test them for cars hands-free nav and PC's etc.

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