IC386 audio amp? - Page 1
Forum section: electronics / beginners

author: etstudent
author_rank: Regular Contributor
timestamp: October 26, 2012, 06:56:34 pm
content: Ok I'm working with an IC386 audio amp. If i want to increase the gain what would I do? Increase or decrease resistance, or increase or decrease capacitance? Its increase capacitance isn't it? If you need more info let me know? Thanks for any help.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 26, 2012, 07:49:11 pm
content: From the datasheet:To make the LM386 a more versatile amplifier, two pins ( 1 and 8 ) are provided for gain control. With pins 1 and 8 open the 1.35 kW resistor sets the gain at 20 (26 dB). If a capacitor is put from pin 1 to 8, bypassing the 1.35 kW resistor, the gain will go up to 200 (46 dB). If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor (or FET) from pin 1 to ground.Since you did not post what your circuit looks like now, it's hard to tell how and if you can get more gain.Most gain (200) you get by just a capacitor (10uF will do) between pins 1 and 8. If that is too much gain put a resistor in series with that, a bigger resistor will give you less gain.

author: free_electron
author_rank: Super Contributor
timestamp: October 26, 2012, 08:51:33 pm
content: Quote from: PA0PBZ on October 26, 2012, 07:49:11 pmhuh ? wtf ? 1.35 kilowatt resistor ? since when are resistor in kilowatts and why would a 0.5 watt amplifier need a 1.35 kilowatt resistor ?and what is with this 1.35 ? what kind of a resistancevalue is that ....must have been designed on paper by a nitwit ( read: theoreticus that is good a abstract math but has no clue what a resistor looks like let alone know how to solder one on a board )

author: etstudent
author_rank: Regular Contributor
timestamp: October 26, 2012, 08:55:05 pm
content: I'm not home, but I know the circuit talked about pins 1 and 8. I'll let you know later more info that is in the question. Thanks for the info already though.

author: SeanB
author_rank: Super Contributor
timestamp: October 26, 2012, 09:08:30 pm
content: Translated by OCR, which confuses the Omega symbol for resistance to a W. Very common on older scanned and OCR'd datasheets, you should see what it does to equations that is does not give up on and store as an image. Just shows the data was not proofed properly and corrected during the process.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 26, 2012, 09:24:44 pm
content: Yeah, I spotted that, hoping nobody would see itAnyway, the advice still stands.

author: etstudent
author_rank: Regular Contributor
timestamp: October 26, 2012, 09:25:48 pm
content: Thanks for the info guys, appreciate the help. Are IC386's not used much anymore? I'm not quite following.

author: ptricks
author_rank: Frequent Contributor
timestamp: October 26, 2012, 11:19:23 pm
content: Quote from: etstudent on October 26, 2012, 09:25:48 pmThe LM386 is still used quite a bit, it is a good chip for low power audio and it is fairly tolerant of things like reverse polarity power, poor power quality, etc and really isn't picky about the board layout either.Oh and it is very cheap !

author: poptones
author_rank: Frequent Contributor
timestamp: October 26, 2012, 11:40:24 pm
content: since when are resistor in kilowatts and why would a 0.5 watt amplifier need a 1.35 kilowatt resistor ?It's biased to operate in class A.

author: etstudent
author_rank: Regular Contributor
timestamp: October 27, 2012, 12:27:41 am
content: OK, thank you very much for the info. Did we come to a consensus, is it lower capacitance? I'll try and add the circuit picture in a but so you can get a better idea.

author: David_AVD
author_rank: Super Contributor
timestamp: October 27, 2012, 12:47:29 am
content: Why not simplytry it?Sigh, doesn't anyone want to actually experiment these days?

author: etstudent
author_rank: Regular Contributor
timestamp: October 27, 2012, 02:00:25 am
content: Yeah I wasn't home, and I took all the components out before I saw a 'test your knowledge" question. Sorry about that. Thanks for the suggestion though.

author: free_electron
author_rank: Super Contributor
timestamp: October 27, 2012, 04:56:32 pm
content: Quote from: poptones on October 26, 2012, 11:40:24 pmoh its one of those western electric lm386's .. the ones that sit in a 9 inch rack, chrome plated knobs and mahogany and rosewood inlaid cover , weight half a ton and can be used to roast 50 chickens simultaneously ...in that case you need to use tar and paper capacitors.. and oxigen free crystallized cryogenically treated interlinks .. you may hear noise from stray electrons ..

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 27, 2012, 05:02:57 pm
content: Quote from: David_AVD on October 27, 2012, 12:47:29 amthey are afraid of being electrocuted so they ask first in case they may try a stupid thing. wise people!

author: T4P
author_rank: Super Contributor
timestamp: October 27, 2012, 05:09:20 pm
content: I keep laughing for some reason while reading this thread.LM386 is quite old but it is still used everywhere. Easy to implement and if you need a higher power chip in DIP the TDA2822M is a good oneNot terribly good PSRR but decent quality even if it was supposed to drive 0.25W/0.5W pancake speakers that have far worse characteristics than the chipamp anyway

author: SeanB
author_rank: Super Contributor
timestamp: October 27, 2012, 08:48:36 pm
content: The speakers you describe are also known as strangled chipmunks. Often you cannot tell the quality of the sound they produce as different than that of the same audio fed into a buzzer.

author: David_AVD
author_rank: Super Contributor
timestamp: October 27, 2012, 10:04:20 pm
content: Quote from: Mechatrommer on October 27, 2012, 05:02:57 pmThis is hardly in the realm of a risky situation.

author: poptones
author_rank: Frequent Contributor
timestamp: October 27, 2012, 11:01:49 pm
content: well, lm386 is awesome. no need to fear, they are also very durable.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 28, 2012, 06:49:09 am
content: Quote from: David_AVD on October 27, 2012, 10:04:20 pmpeople can go hyperphobia with all those advices saying 30 or 90V can kill you and stuffs.

author: Psi
author_rank: Super Contributor
timestamp: October 28, 2012, 07:21:40 am
content: you call that a IC386?THIS is a 386