higher than the theoretical specs say it should. However,
at such a low price ($11.80), it's easy to imagine there
were some design trade-offs to keep the price down while
still delivering reasonable audio quality.
In total, the distortion started just over 1% THD+N at
0.25W into any load and rose to over 10% THD+N at
about 9W, capping out at a total of 19.2% THD+N into a
four ohm load at a maximum output of 10W. Oddly,
neither sample of this module I was sent would deliver
above 5W into an eight ohm load. I did experience some
odd cut-in/cut-out behavior at bass frequencies and when
running it very hard; Rory mentioned he'd encountered
similar behavior on our call.
We determined it occurs when the amplifier exhausts
its current reserve in the onboard electrolytic capacitor. It
would be pretty easy to change out the stock 470 µF
capacitor for a much larger one to improve the low end
performance (Photo 13).
My live listening test confirmed what the meter
measured: a fair amount of background hiss, although not
oo bad at low volume; and distortion growing quickly but
still delivering quite an intelligible signal.
Due to the noise and distortion on this module, I
couldn't recommend it for a hi-fi musical application, but
in a project where audio quality isn't a huge factor it could
certainly get the job done. Guitar amplifiers often have a
fairly high distortion figure anyway, so the self-powered
guitar project is still on the table. Other applications
where you need some volume but won't be playing much
recorded music would also be great — maybe a DIY
intercom or pager project, or built into a small kiosk or
pop-up display to play interface noises and sound effects.
Several forum posts on diyAudio and other Web
communities also report similar performance with
modules based on this chip, and speculate that
performance might be improved by swapping out some of
the surface-mount components for other values and
adding better cooling.
If you're into experimenting, it might be a fun exercise
to get this little module to perform better. The price is low
enough it wouldn't break the bank to try. The underlying
chip has great specs, so if you've got a set of hot tweezers
and don't mind working under a magnifying glass,
modifying the module would probably be an interesting
project unto itself.
Moving up a bit, the model TA2024 amplifier module
(its stock number happens to be the same as the chip)
takes up quite a bit more space, but really does offer a lot
of flexibility — all that extra space means bigger, better
components. There are a set of film input capacitors, plus
an actual sharp-cutoff low pass filter on the output to
remove any residual RF left over after the switching.
The module comes with a small three-conductor cable
PHOTO 14. The
back of the Wi-Fi
Internet radio project
showing an amplifier
module (Nuts & Volts,
PHOTO 15. THD+N vs. power for the Tripath TA2024 chip,
from the manufacturer's datasheet.
50 March 2015
PHOTO 13. PAM8610 THD+N measured into four and
eight ohm loads from 0.25W through maximum power