making this tiny audio amp cleaner?

[daz]

Can anyone tell me how i could change this circuit to get a bit more clean power? I know theres only so much you can do with a PA like this, but any improvement would likely make it usable whereas right now it's just not quite loud enough before it becomes distorted.

http://web.mit.edu/6.s28/www/schematics/lm386.htm

[Jazz P Bass]

What supply voltage did you use?
There are different suffixes of the LM386.
Which one did you pick.
The LM386N-4 is good for 1 watt output, at 32 ohms, with a 16 volt power supply.
Louder is going to take more voltage in the power supply & a different IC.
This chip is teeny weeny as far as output.

[daz]

I tried 9v, then 4.5 with 3 AA's. If anyone knows of a cleaner tiny circuit like this with common parts please tell me. chip says LM386N-3

[Jazz P Bass]

I do not know what you are after.
Here is a TDA2030 IC.
If current draw is a problem, don't turn it up.

[Mark Hammer]

For powering an LM386 amp, I like to use an octet of AAs or AAAs for 12V. If you're aiming for cleanliness at reasonable volumes, you need current, and a 9v battery won't cut it. With a 12v supply, the speaker should not be lower than 8 ohms however, unless you find some way to heat sink the chip.

The schematic you link to runs it at maximum gain. The path between pins 1 and 8 dictates the gain. With nothing linking them, the chip defaults to its internal lower-gain path. Running a cap like C2 from pins 1 to 8 sets the chip at max gain.

Looking at the internal schematic in the datasheet you can see that resistances lower than 1.35k increase gain for whatever portion of the spectrum is passed. You can provide multiple paths if you wish. So, you could run one network with 1k and 10uf for a bit more than the default gain for the entire spectrum, and a second network of, say, 680R and .01uf for a little bit more oomph for the top end.

It obviously won't be a 1W McIntosh or Crown, and 1W is not going to shake the room, but it will sound about as good as it can. You will also find that using an efficient speaker and cabinet can squeeze a lot more out of that puny little watt.

[daz]

Well, i should have described the usage because that will eliminate certain suggestions and prompt others. I intend to build 2 for stereo powering some small 8 ohm speakers out of a boombox and use it at a campsite to amplify a mp3 player. I bought a unit that does just that, but it sounds lousy so i'm returning it. This one i breadboarded sounds quite good thru a big speaker, but it cannot get a small speaker to get loud enough before distortion because the SPL is too low and causes me to have to crank the amp till it distorts.

[Ronsonic]

When you are that limited for power speaker efficiency is everything. You'll have to decide whether to find a driver with another few dB of efficiency or carry more batteries for a bigger amp.

[km6xz]

The 386 is a easy chip to use but that is about the only benefit because they are not efficient enough for battery operation, but not many Class AB designs are.
A better bet for this application would be the very low cost Class D amp chips which have much better performance at 3-5 volts.
Try the Analog Devices style using Sigma-Delta modulation, they do not require the usual lowpass filter at the output.
A good one is for your need is the SSM2317 which outputs 3 watts into 3 ohms on single 5 volt supply at surprising low current. It has 93% efficiency, 93db S/N and needs few external parts. Idle is 4ma.
http://www.analog.com/static/importe...ts/SSM2317.pdf

You will likely not even need a heat sink.
They make stereo chips and some can be configured for bridge operation if you really want power. I used one in a little signal sniffer, using a 3.6 volt wireless phone battery. I've used it intermittently for 3 months and never recharged the battery yet develops 1.5 watts out. The whole amp board including switch and gain control is 2 x 1 inches
There is only one hitch.... it is a ball grid array chip, no leads and only 1.5mm on a side. I glued it upside-down on a copper clad board and wired to it with a 10 power magnifier light.
A regular SMD SMOP case, 3 mm on a side that is big enough to solder the leads style is for example the SSM3305 or the stereo version SSM3304.
Good luck

[MarkusBass]

I think you ment SSM2305: http://www.analog.com/static/importe...ts/SSM2305.pdf available in MSOP package. Maximum power supply is 5V so it will work very well with 3 AAs.

Mark

[J M Fahey]

If you want to rock that camp I'd start by specifying a 12V 7A gel battery (the one commonly used in alarms) which is about as much as you can carry comfortably, and build a lightweight 3/8" plywood box (forget MDF) , stuffed with said battery, 2 bridged typical car power amps (I use bridged TDA2005 but there are much newer and simpler versions) driving 2 Jensen MODs in 4 ohms; maybe 8" or 10", as large as you have space for.
Even 2 x 12" for a still carryable "Twin" size amp.
2x16 **clean** RMS watts, very loud because of the high efficiency (in their class) speakers, much louder than any similar priced Hi Fi or car ones.
A couple piezo tweeters in parallel with each speaker will give you highs, or even better, a couple of those LeSon Piezo tweeters (the ones used by SWR) which are unbearably loud.
You can easily power an outdoor party with such a system.
I do
PS: *forget* about chest-thumping bass, of course.
As an example, here you have one such amp: 16W RMS into an internal 8" plus a LeSon tweeter, and you can plug another similar cabinet for 32 W; everything powered by said battery.
The charger is built-in.
I split it in two because it's used by two aging Tango players, it's easier for them that way.

[daz]

Thanks all, but as one of you said speaker efficiency was the key, tho along with a few tweaks that helped a bit too. Oddly the speaker was loud and efficient in the player it came in, but not with this amp. Using a PC speaker instead yielded infinitely better results. I have the stereo sides tied together (somehow no odd cancellations or any of that even w/o mixing resistors...i thought that would happen) and using the unpowered speaker from a cheap PC set and it sounds quite good even using a 9v. I will bring a bag of 8 9v's i have with me in case it eats them quickly, but so far seems like one should last a couple hours at the low volumes i require.