siliconchip.com.au Australia’s electronics magazine July 2019 91
... Screen09: the first
adjustment, which allows
you to adjust the lower
-3dB point using the rotary
encoder, to as low as 15Hz.
Pressing S1 will take you
back to the volume screen,
or press S2 to go to...Screen10: the second
crossover adjustment, the
upper -3dB point, which
goes as high as 15kHz.
Here it is set to 199Hz.
Pressing S2 takes you to...Screen11: the lower slope
adjustment. You can select
None, 6dB/octave or 12dB/
octave Butterworth, or
24dB/octave Linkwitz-
Riley filters. Then press S2
to go to...Screen12: the upper slope
adjustment, where you
have the same options.
Press S2 again to go to...Screen13: the delay
adjustment, allowing time-
compensation of drivers
in a speaker cabinet. The
setting (up to 6239mm) is
converted to a delay based
on the speed of sound.
Press S2 again to go to...Screen14: the attenuation
adjustment, which can
be set from 0dB down to
-20dB. It can be used to
compensate for different
driver efficiencies etc.
Pressing S2 again takes
you to...Screen15: the option to
invert the signals for this
output, which may be
useful if you have drivers
wired out-of-phase.
Rotating the knob...Screen16: selects inverted
mode, while rotating it
further returns to normal
(non-inverted) mode. One
more press of S2 takes you
to...shown in Fig.6 on page 35 of the May 2019 issue, CON16
connects to CON2 on the ADC board, while CON14 goes to
CON3 on the first DAC board (woofer output) and CON15
goes to CON3 on the second DAC board (tweeter output).
As with the other cables, be careful to make sure that
the pin 1 side of each plug goes to the pin 1 marked for
each header, and that you don’t plug them in offset by one
row of pins.
All the ADC and DAC boards have pin 1 on the side of
the header closest to the nearest edge of the board, and
similarly, on the power supply/routing board, pin 1 of each
header is towards the bottom edge.
We specified three different cable lengths last month,
since these three boards will be different distances from
the power supply module.
In our prototypes, the ADC board is closest, so it uses the
shortest cable; however, there’s nothing to stop you from
using a different arrangement.
Once those are all plugged in, check that JP1-JP4 are
inserted and that LK1 is set to SDO4. The only way to re-
ally test it is to connect a signal source to the ADC inputs,
power the unit up and check that you’re getting appropri-
ate signals from the four outputs, using either a scope or a
power amplifier and speakers.
If using an amplifier, turn the volume down initially in
case there’s something wrong; otherwise, your ears may
get blasted!
If you don’t get the expected result, check that all the
jumpers are in the correct positions (see last month).
Preparing the rear panel
The steps for final assembly are: drill and cut holes in
the front and rear of the case, determine the ideal location
for each module and mount them to the case, attach the
LCD and control board to the front panel and then com-
plete the wiring.
On the rear panel, you will need to drill six holes of
9-10mm diameter for the RCA sockets. Ideally, you should
also drill a 3mm hole for each pair of RCA sockets, to
mount the connector to the rear panel so that it isn’t dam-
aged when pushing the plugs in. The hole pattern required
is shown in Fig.23.
Each group of holes will need to be at least 60mm apart,
to give room for the boards to fit side-by-side. You may
wish to increase the space between the ADC module and
the two DAC modules (assuming your case is large enough),
to make the distinction more obvious.
On the rear panel, you will also need to mount either a
concentric socket for a plugpack or a mains cord or socket
(ie, an IEC input socket).
While it’s a good idea to also fit a fuseholder to the rear
panel for the plugpack-powered version, it isn’t strictly
necessary. However, you definitely need a fuse if using a
mains power supply. Our second prototype, shown in the
photos here, is plugpack-powered.
Mains wiring
For a mains supply, if you’re fitting an IEC socket for con-
venience (wired-in or “captive” mains cords can be a bit
of a pain), you can use one with an integral fuse and then
you won’t need to mount a separate fuseholder.
But note that IEC sockets with fuse holders often have
exposed, live conductors on the inside, so it’s a good idea