Connect your speaker to the OUT + and - header. If you're using one speaker the
polarity doesn't matter, but if you'll be using multiple speakers, ensure that you wire
them all the same way to avoid phase problems. The speaker can be 4 or 8 Ohms.
The maximum output of the amplifier is 1.4 Watts into 8 Ohms. You can drive smaller-
wattage speakers with this amplifier, but you should be careful not to turn up the
volume too high to avoid damaging the speaker. You can also drive speakers larger
than 1.4W at reduced volume. In general, larger speakers will sound much better than
smaller speakers; we've had great luck with old automotive speakers.
Connect a power source to the + and - pins. The power source can be from 2.5V to
5.5V, and should be able to source at least 280 milliamps if you want maximum
volume. The red LED will illuminate when the board is powered up.
Apply an audio signal to the input, and you should be able to hear it on the speaker.
To change the volume, either change the volume of the signal at its source, or add a
volume-control potentiometer to the board (instructions below).
Adding a volume control knob
If you wish, you can easily add a 10K volume control potentiometer to this board. The
volume control will let you control the volume by reducing the input signal from 100%
to 0%. Note that this will not make the amplifier any louder - if you'd like to do that,
see changing the gain resistors below. Here's how to add a volume control
potentiometer:
Remove the solder from jumper SJ1. This is the small blob of solder within the white
brackets on the bottom right of the board. The easiest way to do this is to apply solder
wick to the jumper, and heat it with your soldering iron. When you're done, ensure
that the two sides are electrically separated from each other.
Now, connect your 10K potentiometer to the three pads on the lower right of the
board. The bottom of the board has silkscreen showing the proper connections. You
can solder a trimpot with 0.1"-spacing on the pins (such as COM-09806) directly to
the board, or you can use wires to connect the board to a larger potentiometer in a
chassis, etc.
Note: Potentiometers come in two styles: "linear taper" and "audio (or logarithmic)
taper". Audio taper potentiometers have a logarithmic bias that give a more natural
feel in audio volume control applications like this one, but linear taper will also work
just fine.
How to use the shutdown pin
The SDN* input can be used to turn off the amplifier to save power when it's not being
used. When SDN* is disconnected, or connected to a high logic signal (> 2V), the
amplifier will function normally. When the SDN* pin is connected to ground or a low
logic signal (< 0.8V), the amplifier and LED will turn off. You can use this feature to
save power in battery-operated projects.
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