compact portable amplifier dual lm386

irishlyrucked · 12th June 2010, 06:59 PM

I built a set of speakers in altoids tins: Portable Altoids Speaker System

The only problem with the setup is a lack of volume being driven from my portable devices. Since I mainly use this when I'm on short camping trips, or outside with all the natural noises associated with that, I wanted an amplifier that I could fit in the same size packaging. So I've been looking around, and I found a few circuits that might do it, and I blended them together so I could get a stereo amplifier that would fit in a mint tin.

If you look at the attached picture, you'll see the schematic. I'm really looking for any advice or criticism on the circuit design. Also, if you like it, feel free to use it. I'm more than willing to email the eagle sch files to anyone who requests them.

wakibaki · 12th June 2010, 08:47 PM

You take this ear-destroyer out in the countryside and disturb the wildlife? Then you have the nerve to come on here and boast about it? Yeah, we got people here running tubes in class A, but what kind of eco-vandals do you take us for?

w

Circuit looks half good. Maybe I could use it to upset the neighbours...

irishlyrucked · 12th June 2010, 09:07 PM

well, it is only pushing 2W total in this design. So I wouldn't exactly call it an ear-destroyer.

It really only needs enough sound to be heard over small campfires. And there's no way I'm lugging around 2 9v SLA batteries to run anything harder than this.

irishlyrucked · 12th June 2010, 09:22 PM

I wouldn't really call it an ear-destroyer. It's 2W total.

AndrewT · 13th June 2010, 10:31 AM

Is the amp running on a single 18V supply?

irishlyrucked · 13th June 2010, 03:31 PM

Yes. It is going to be powered by 2 9v batteries in series.

AndrewT · 14th June 2010, 09:41 AM

then the input pins +IN & -IN must be biased to ~ half supply voltage, not grounded to the lower supply rail.

AKN · 14th June 2010, 09:54 AM

Quote:

Originally Posted by AndrewT

then the input pins +IN & -IN must be biased to ~ half supply voltage, not grounded to the lower supply rail.

Hi Andrew T,
No, have a look at the LM386 data sheet http://www.national.com/profile/snip.cgi/openDS=LM386

AndrewT · 14th June 2010, 10:41 AM

you have read the datasheet correctly.
I take back my suggestion.

irishlyrucked · 14th June 2010, 10:47 AM

Yeah, that got me too, when I was first designing this. I've never used the chip before. I'll be ordering parts this week, and hopefully, I'll have it together next weekend to let you all know how it performs.

13th June 2010, 10:31 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Is the amp running on a single 18V supply? __________________ regards Andrew T.

14th June 2010, 09:41 AM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	then the input pins +IN & -IN must be biased to ~ half supply voltage, not grounded to the lower supply rail. __________________ regards Andrew T.

14th June 2010, 10:41 AM	#9
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	you have read the datasheet correctly. I take back my suggestion. __________________ regards Andrew T.

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12th June 2010, 08:47 PM	#2
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	You take this ear-destroyer out in the countryside and disturb the wildlife? Then you have the nerve to come on here and boast about it? Yeah, we got people here running tubes in class A, but what kind of eco-vandals do you take us for? w Circuit looks half good. Maybe I could use it to upset the neighbours...

12th June 2010, 09:07 PM	#3
irishlyrucked diyAudio Member Join Date: Feb 2010	well, it is only pushing 2W total in this design. So I wouldn't exactly call it an ear-destroyer. It really only needs enough sound to be heard over small campfires. And there's no way I'm lugging around 2 9v SLA batteries to run anything harder than this.

12th June 2010, 09:22 PM	#4
irishlyrucked diyAudio Member Join Date: Feb 2010	I wouldn't really call it an ear-destroyer. It's 2W total.

13th June 2010, 03:31 PM	#6
irishlyrucked diyAudio Member Join Date: Feb 2010	Yes. It is going to be powered by 2 9v batteries in series.

14th June 2010, 10:47 AM	#10
irishlyrucked diyAudio Member Join Date: Feb 2010	Yeah, that got me too, when I was first designing this. I've never used the chip before. I'll be ordering parts this week, and hopefully, I'll have it together next weekend to let you all know how it performs.

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