38 Silicon chip Australia’s electronics magazine siliconchip.com.au
Bargain Class-D Stereo +
Subwoofer Amplifier
Modules
The old
saying says
that “if it sounds
too good to be
true, it probably is”.
So if we told you
that you could get an
assembled 3 x 50W
amplifier module for under
$US6, you would probably
be thinking that it would be a load of junk.
But in this case, that isn’t the case! This one works almost (!) as well
as advertised – and most of its shortcomings can easily be addressed.T
he Class-D 3 x 50W amplifier
module (stereo plus subwoofer)
shown above can be purchased
(at time of going to press) for about
$US6 from eBay or AliExpress.
For a bit more money, you can get the
5x50W amplifier module with built-in
Bluetooth support shown opposite.
Both run from 5-27V DC, provide
decent performance and appear to be
very good value for money.
The XD172700 module
The module above uses the latest
power IC from Texas Instruments, the
TPA3116D2 IC (2017 revision G), who
describe it as a “15W, 30W, 50W Filter-
Free Class-D Stereo Amplifier Family
With AM Avoidance”.
The chip measures just 11mm x
6.2mm. Two are used on the first board:
one is used in stereo mode for the left
and right channels and the other in
mono (bridged) mode for driving a
subwoofer.
These amplifier chips are fed audio
by two NE5532 ICs used as preamp-
lifiers and to provide the subwoofer
low-pass filter.
You don’t have to worry about sol-
dering the SMD TPA3116D2 chips be-
cause this has all been done for you!
Our suggested modifications require a
little bit of soldering.
We paid sixteen dollars (Austral-
ian) including postage – and are feel-
ing miffed at that, having since found
them much cheaper! The board comes
with everything, even the kitchen sink,
err, heatsink, which is shared by both
amplifier ICs.
It even came with a set of standoffs,
nuts and bolts for mounting it in a
chassis, plus a nice set of shiny knobs
for the pots! All you need to do then is
wire up the power supply, audio input
and speaker output terminals.
The board has two audio input op-
tions: you can use either the 3.5mm
stereo jack socket or a three-pin JSTheader. And there are two options for
power supply; either a PCB screw ter-
minal or a 5.5mm DC barrel socket for
a plugpack or inline power supply.
The board requires a simple DC sup-
ply, and this simplifies things signifi-
cantly because you can use just about
any supply that produces 5-24V DC
such as an old laptop supply or any
other high current source, including
a car battery, electric drill battery etc.
You could even use a 5V USB charger.
But to get the full output power, you
need around 24V at 6-7A.
Note that to get the full power out-
put you will also need 4Ω speakers.
Higher impedance speakers cannot be
driven to quite as high power levels.
For example, if you use 8Ω speakers,
with the appropriate power supply,
you will get around 30W maximum
from the left and right channels.
The amplifier ICs have a high power
supply rejection ratio (PSRR), so you
don’t need a super smooth DC supply.PCB size is
100 x 70mm.