Better and worse LM386M amplifiers

I've been soldering two copies of the same circuit with brand new LM386M and I realized that first one has literally zero noise (unless I touch the potentiometer pins), and second one has a constant, loud noise (but still reacts to touching pins).
I've been testing both circuits with the same speaker.
I have investigated it, swapped the LM386Ms and found out that most likely one of the LM386M is the culprit.
I have replaced the noisy LM386M with an another one and now everything is ok...

Did anyone here experience similiar problems?

Does it means that LM386M has a different audio quality from batch to batch or did I get unlucky and bought a broken chip?

Hi,

Did you take care to avoid ESD?
I'd say that a "almosed damaged" input of an Opamp causes increased noise by a destroyed isolation barrier.
But I'm no expert in this.

Klaus

The LM386 is simple and cheap. It is not used in hifi's, instead it is used in kid's toys. Some are noisy and some aren't.
If you want a hifi amplifier IC then buy a hifi amplifier IC. It will have less noise, less distortion and much more maximum output power. The manufacturers throw away the bad ones or sell them to ebay.

Audioguru said:

The LM386 is simple and cheap. It is not used in hifi's, instead it is used in kid's toys. Some are noisy and some aren't.
If you want a hifi amplifier IC then buy a hifi amplifier IC. It will have less noise, less distortion and much more maximum output power.

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The OP did not mention striving for hifi quality or high power. The LM386 was designed and introduced by NatSemi, one the most respected manufacturers of analog ICs. It has been copied by other highly respected companies. It fills a niche where the target is to produce audio of reasonable quality with a cheap and compact IC that's simple to use with just a few external components.

It's not used just in toys. I've used it in some of my professional designs, especially where sound is only one part of a more complex system. So have many other skilled designers and major companies.

The manufacturers throw away the bad ones or sell them to ebay.

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Do you have evidence of this? I don't think any reputable company will sell their bad products on eBay.

The OP may have unknowingly bought a counterfeit or the IC may have got damaged at some stage.

Pjdd said:

The OP did not mention striving for hifi quality or high power.

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The Op has a noisy one and a quiet one. He asked if there is different quality from batch to batch or if he has a bad one.

The LM386 costs $1.01US at Digikey today. Its output is only 0.45W before clipping into 8 ohms with a 9V supply and its distortion is 0.2% when the output is only 0.125W. Its noise is not even mentioned. Cheap.
The LM1875 costs $3.16US today. Its output is 20W into 8 ohms with very low 0.015% distortion. Its low noise is listed on its datasheet. Hifi.
Maybe ebay sells defective used LM386 ICs taken from toys, or maybe cheap toy manufacturers sell the bad ones on ebay.

And the point of all that is......?

The OP asked a straightforward question but your reply went off at a tangent. The LM386, like many many other products, was designed to fill a niche and it does that very well. Your disparaging remarks about it could mislead and discourage less experienced people. The same points could have been made in a different tone. That was my point.

BTW, I can get the LM386 for the equivalent of 20-25 US cents in my country. They're available from China for 6 cents each, with free shipping. I've actually tried those too and they're OK.