I was pondering how I was going to amplify the signal coming out of my AD9833 signal generator module, to drive my MakerHawk 3 watt, 8 ohm speaker. Then I found an LM386 IC in my box of assorted op-amps. I found this amplifier to be easy to use, especial with the example “minimum parts” circuit in the data sheet:
In the picture at the top of this post, you can see the AD9833 module, but I’m actually trying out the amplifier chip by driving it with a desktop signal generator, which is connected to the leads on the left. With the signal generator set to as little as 100mV p-p, I had no trouble hearing the sound on the speaker with 1khz, 1.5 khz, and 2 khz tones. The sound was quiet and distorted at 500 Hz and lower, but that would be expected of such a small speaker.
The Uno in the picture is not providing the LM386 input signal in this test, but is simply providing the 5V supply voltage.
Some caveats; the LM386 requires at least 4V supply voltage, which is a problem for folks who want to use their microcontrollers with a lower 3.3 V supply only. Also, I think the AD9833 generated a 700 mV p-p signal when I tried it last week, which I believe fits just inside the LM386’s range of minimum -4V and maximum +4V input signal — probably you will want a voltage divider or volume control to attenuate the signal some.
The Libre Hacker 