The only way I know to improve the noise performance is to lower the gain of the LM386 and use a low noise opamp at the mic end to make that gain back up. That way, by the time the signal reaches the LM386 and its considerable noise contribution, the signal is quite a bit stronger, in comparison. But this would require a complete board redesign or add on board.
Rob, the main reason why you find this power amp inside the appliance is certainly its low cost (0.19$). It will drive loudspeakers directly with up to 1W power. Unfortunately the amp has a specialized pinout and can not be replaced so easily with an ordinary opamp, even if you would use only headphones and do not need the driving features. The bias scheme and the gain adjustment have to be modified. Maybe when you post the circuit in ABSE or elsewhere, somebody could be of more help.
Blimey ! I didn't think the LM386 was even still available ! It was fairly rubbish when it was designed and is certainly no better now.
There's nothing that'll drop in to replace it.
Graham
Evening all. Wndering if anyone can help. I have a basic amplifier which I made from a kit called a 'Super Snooper', distributed by Oatley Electronics in Australia. It uses the LM386N-1 package to amplify minute noises via an electret mic. It works fantastic and will even pick up the sound of my watch ticking in the table next to it. One problem. There is substantial hissing in the background. Is there any way in which to reduce or eliminate this hissing? Another question. Is there another amp chip, comparative to the LM386N-1 which will possible do the same job, but with less noise. don't care if it costs more. Thanks in advance to any replies Rob Fonhof Melbourne Australia
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replace LM386 amp with something decent. Probably the most lowdown dirty IC amp I've ever used.
NT
IIRC the std amplification (no feedback resistors added) is 20x - do not ask more of it! If adequate anti-oscillation ckt is added (the common 100n / 10 Ohm network), I find the performance of ye olde amplifier (-1 type is 500 mW?) working adequate for simple tasks. Added amplification can be added using a simple one transistor ckt as "frontend" (not always opamps, 555's or Pics are required :-). Cleaning up the "frontend" power with a RC ckt (560 Ohms, 220 uF or such) does help too.
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