Look on eBay for a PAM8403-based amp.
I ordered 10 of them for 7 bucks! It looks like the perfect answer. I need only one channel instead of two, but for such a low price, who cares. :)
The LM386 is so popular because it has been around for a long time....
Class-D amplifiers are much more efficient....
Voltage swing on the speaker can be doubled with two amps in bridge, with the speaker in between.
Twice the voltage is four times the power.
Dynamic impedance is very frequency dependent, and usually lowest at ~500hz.
Thank you for a lot of valuable information (and in only a few words).
I didn't even know about "Class-D Amplifiers". But just now read that they "operate as electronic switches, instead of as linear gain devices". Which means they are constantly switching between no resistance, and no current; resulting in a controlled total current without ever having "resistance" to eat up part of the power; it all goes to the speaker instead! Sounds great! :)
You're idea about using two amplifiers to achieve twice the voltage is a great one, I almost tried it with two LM386 amps. But then realized they are clearly clamping the current to a particular level, not the voltage. And since all current would be passing through both amps in series, the total amperage through the speaker (and thus power) would remain the same. However, I wonder about connecting two LM386's parallel to each other, and to the same end of the speaker. Then they could supply twice the total current (and so four times the power), each then able to produce that 4 volts I saw with no speaker.
A normal USB port is limited t0 500 ma, so thats a maximum power of 2.5 watts.
To get more you will have to provide a hi power USB port, or a powered USB hub.
Very helpful to know! I'll stick with the 2.5 watts for the sake of my customers and their USB ports.
Thank all of you who answered. You've supplied a wealth of information, and I'm taking in every word. I've ordered the new amplifiers as suggested. So my question is now fully answered!