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LM386 minimal circuit

gary350

Well-Known Member
#41

audioguru

Well-Known Member
Most Helpful Member
#43
The LM386N-4/nopb data sheet says 1 watt
Where can you buy a 32 ohm speaker?
Have you heard how bad 10% of clipping distortion sounds? The volume is turned up too high to make the output power number bigger with lots of distortion.

Yesterday I found an LM386????? in a different package it has a heat sink tab datasheet says 1.5 watts. I wish I had written down the part number. If anyone finds this I want the number I might buy 1 to experiment with.
There are many audio amplifier ICs made.
Did you know that 1.5W sounds only a little louder than 0.75W? 10 times the power sounds twice as loud because our hearing's sensitivity to loudness is logarithmic. The Chinese amplifier manufacturer doesn't know that so he used the wrong volume control. It is marked "B" which is linear like in a power supply. A logarithmic volume control is marked "A".

Ebay has LM386 amps from china 99¢
Is the IC a cheap poorly made Chinese copy?
The volume control is wrong, what else is wrong?

Don't believe everything you see in a datasheet because NOOB employees get stuff wrong.
 

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gary350

Well-Known Member
#44
Where can you buy a 32 ohm speaker?
Have you heard how bad 10% of clipping distortion sounds? The volume is turned up too high to make the output power number bigger with lots of distortion.


There are many audio amplifier ICs made.
Did you know that 1.5W sounds only a little louder than 0.75W? 10 times the power sounds twice as loud because our hearing's sensitivity to loudness is logarithmic. The Chinese amplifier manufacturer doesn't know that so he used the wrong volume control. It is marked "B" which is linear like in a power supply. A logarithmic volume control is marked "A".


Is the IC a cheap poorly made Chinese copy?
The volume control is wrong, what else is wrong?

Don't believe everything you see in a datasheet because NOOB employees get stuff wrong.
50 years ago when I could HEAR the 8 watt amplifier that I built was LOUD, now I can barely hear it. No way I can hear 1w or 1.5w anymore without ear phones. I am learning new things and having FUN that is what an old retired fossil does. LOL :)

Years ago I built 2 hearing aids with LM386 it has gain control and volume control they work great but 9v batteries dies fast and 8 D batteries are big and heavy. I think hearing aids will work better with improvements like filter circuit to amplifier Hz that I have a hard time hearing. I have been studying filters not sure how to put this together, should filters be on input or output side of LM386.

I bought hearing aids that work great but it would still be FUN to lean how to make the LM386 hearing aid circuit better.
 
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gophert

Well-Known Member
Most Helpful Member
#48
That circuit will pop hard when power is turned on. Also, it is not capacitively coupled and DC will be flowing through the headphones. That will heat the voice coils and make them hot in your ear (or even burn them out). Headphones (all speakers) are intended to be used with very low/no DC component.
 

chemelec

Well-Known Member
#49
When Connecting an Amp to headphones, You should Always Include a Current Limiting Series Resistor.
The Value of this Resistors will be Determined by the Impedance of the Headphones.+
With Older 8 Ohm Headphones, a 100 Ohm resistor is Suitable.
With Higher Impedance ones, Possibly use 1k Ohm or more.
 

audioguru

Well-Known Member
Most Helpful Member
#50
The Best Engineering Projects website is written by a student in Nepal (NE mountains of India) who obviously knows NOTHING about electronics.
1) The LM358 is horrible for audio because it has crossover distortion, has a high noise level and has poor high audio frequency response.
2) As already mentioned, since both opamps are not biased properly then they are rectifiers that produce severe distortion.
3) Almost all old people (like me) need the high audio frequencies boosted a lot. This circuit does not Doo Dat.
4) As already mentioned, the earphone has DC in it to fry it, the DC will also cause the diaphragm to be pressed against one side so it might produce no sounds. The DC in the earphone will kill the battery quickly.
5) The battery is only 3V which is the minimum supply for an LM358 dual opamp so when the battery runs down a tiny amount then the IC will not work.
6) The positive supply is missing an important filter capacitor.
7) Why have R1 and R2 in series without a filter capacitor to ground between them?
8) The value of R2 is too high with the very low supply voltage so the electret mic receives a current that is too low and it will barely work.

Here are graphs showing high frequency loss of old people. The high frequencies are reduced a lot. My modern hearing aids are tiny and are programmed to restore the reduced high frequencies perfectly. My hearing produces low frequencies perfectly then the hearing aids do not amplify low frequencies.
 

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audioguru

Well-Known Member
Most Helpful Member
#51
Looking at the horrible hearing aid circuit again, I notice that the opamp (+) inputs have 100k resistors to ground but the (-) inputs have only 10k. Then the different input offset voltages will be amplified by the opamps and bias them a small amount But many opamps will have a very low input bias current that will produce such a low bias voltage that the output transistor will be turned off most of the time and do nothing. Then the earphone and battery will survive.
 

unclejed613

Well-Known Member
Most Helpful Member
Thread starter #52
The Best Engineering Projects website is written by a student in Nepal (NE mountains of India) who obviously knows NOTHING about electronics.
LM358 is basically a dual 741
he's also got 5 pages of 741 projects. there's no reason to use a 741.... for anything.... unless you inherited a lifetime stockpile of them... they're not even good enough for use in a power supply unless you are desperate...

"back in the day" i was in a rock band, and we were trying to make a demo tape. the drummer brought a cheap 10 channel mixer to rehearsal to try out, so we tried making a tape using this mixer. it sounded like we were outside in the rain, there was that much hiss. so i opened it up, and there were a pair of 741 chips in sockets. we went to radio shack and bought a pair of TL081s and replaced the 741s. the hiss was gone, the audio was a lot clearer and cleaner (good thing they were socketed too). TL081 op amps aren't even the best op amps for audio, but they were still a huge improvement.
 
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gary350

Well-Known Member
#60
I use to put videos on photo bucket but now they charge a fee for me to see my own pics and videos. I can not delete or upload more videos unless I pay the fee so i don't go to photo bucket anymore. Maybe there are more places to upload video for free I don't. I list pictures on Craigslist it is free but not videos. Camping forum and garden forum does not do videos even if I link a video to their web page. Ebay does not do video only photos. Facebook does video and photos but you can not view them unless your log onto to facebook. Never been to twitter it is probably same as facebook.

3 more months of winter cold weather need to find something to do, need more projects to build. Wish I had a simulator it would probably be fun.
 

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