USB
Part 3
By Phil Prosser
Over the last two issues, we’ve
introduced our new USB Sound Card, which we’ve
dubbed the SuperCodec, and described its performance and operation
in some detail. You would agree it offers extremely high recording and
playback performance – so much so that our Audio Precision system can
barely even measure its distortion! Now it’s time to put it all together, and
get it up and running.
I
t’s best to build the SuperCodec in stages,
checking after each stage is complete that everything you
have just assembled is working properly.
Before starting, check that the PCB slides neatly into
the case. This board is specifically made to fit a Hammond
1455N2201 case, which is sold by both Altronics and Mouser,
as stated in the parts list published previously.
The part codes given are for the case with black end panels,
as we have used, but note that Mouser stocks it in several other
colours too. Now let’s move on to mounting the components
on the PCB.
Mounting the pre-regulators
Loading this section is pretty straight forward, as it is all
through-hole. The PCB has a section marked to indicate this
part of the circuit.
Referring to the PCB overlay diagram, Fig.17 and the
photograph alongside (which you should do throughout the
construction process), this section is at lower right.
Start by fitting the six resistors in this section, in the positions shown in Fig.17. Follow with the three diodes, D1
(1N4004) and D2-D3 (1N5822).
Note that they are not all aligned in the same direction.
They have been oriented to minimise path length and radiation loops, so double-check that your diode cathode stripe
is aligned as shown in the overlay diagram and on the PCB,
before soldering each.
Next, install the seven MKT capacitors, which are not polarised, followed by the DC input barrel connector and the fuse
clips, marked F1. Then you can fit the eight electrolytic capacitors; these are polarised, so their longer (positive) leads need to
go into the pads nearest the + marks on the PCB and in Fig.17.
Make sure that the 2200µF 10V capacitor goes to the right,
as shown by the smaller circle, with the larger 2200µF 25V
type to its left. Also ensure that the two 470µF capacitors fitted in this section are rated at 25V; the 470µF 6.3V capacitor
goes elsewhere.
You can then solder LED2 in place. For now, mount it vertically, with the base of its lens 10mm above the top surface of
the PCB. Make sure its longer anode lead goes into the pad
marked ‘A’.
It’s then time to solder switchmode regulators REG1 and
REG2 in place. They have five pins; if yours are all in a row,
crank them out with needle-nose pliers to fit the pad pattern
on the PCB. They don’t need heatsinks.
Now solder the inductors to the board. L1 and L3 are both
bulky toroidal types while L2 and L4 are smaller bobbin types.
Put a dab of RTV or neutral cure silicone sealant under each
inductor to help hold it into place, and prevent vibration, as
shown in the photo overleaf.
Oh no! I’ve put an IC in the wrong way around!
Everybody makes mistakes! So what to do
if you got a part the wrong way around or
in the wrong spot?
For through-hole parts, there are two
ways to proceed. For electrolytic capacitors, you are best off using a solder sucker
to get as much of the solder from the holes
as you can, then judiciously heating one pin
and ‘pushing’ the capacitor to lever up the
component on the hole you have hot. Be
careful and make sure that the leads are
straight and will not tear the through-hole
plating out as they go.
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For op amps, resistors and diodes, the
easiest and safest way by far is to cut the
component from its leads, then remove the
leads individually from the board and clean up
the holes. It sounds wasteful, but this could
save you tearing a track from your PCB, a
lot of frustration and many naughty words.
Surface-mount parts are much easier to
remove with a hot air gun. Set it to about
300°C, heat the part until all the leads come
loose and use tweezers to lift it free of the
PCB before the solder solidifies – job done.
If you don’t have one, you can alternatively
heat each side of the part until it comes
loose. If it’s an IC, this is easiest to do
if you join all the pins on each side with
one big blob of solder. It’s easy enough
to clean up afterwards.
If you won’t pay what your local
electronics shop is asking for a hot air
station, look on eBay; there are ‘decent’
hot air guns available at giveaway prices.
Search for ‘hot air SMD rework’; some are
well under $100. These are brilliant for
heatshrink work too. Note that it’s best to
keep these switched off when not in use!
Practical Electronics | November | 2021
Finally, add the 0Ω link; we
used a length of 0.7mm tinned
copper wire bent to form an
Earth connection point, but
you can also use a zero-ohm
resistor, as shown on the PCB
overlay diagram.
Testing the pre-regulators
Connect a voltmeter from
ground (eg, either end of the 0Ω
link) to the near end of FB12’s pad. This
is a convenient point to measure the −12V rail,
as marked on the PCB.
Connect your 12V DC plugpack to CON1. The specified plugpack is a switch-mode unit capable of delivering at
least 1.5A continuously. Switch on the power and look for
the −12V rail coming up. Check that it is between −11 and
−13V. Ours measured −11.5V.
Then move the red probe to the near end of FB8 (another
empty pad) and check that the +6.5V rail measures 6.0-7.5V.
Ours was close to 7V.
Finally, move the probe to the near end of FB11 and check
that the +12V rail is OK. It will possibly be close to 11V due
to the forward voltage drop of diode D1.
You can then disconnect the plugpack and proceed with
the construction. If any of the readings are off, look for short
circuits or bad solder joints. Also make sure that your plugpack has the current capacity to kick that negative regulator
into operation.
Mounting the linear regulators
This section is positioned in the middle of the board and
includes regulators REG3, REG4, REG6-REG8 and the surrounding components.
Start by loading all the ferrite beads in this section, FB8
through FB13. These can be any small ferrite that fits; they
are there to offer a high impedance at high frequencies to
keep the noise on the rails down.
If your beads came loose (as they often do), feed component
lead off-cuts from the previous section through each one before
soldering, or sections of tinned copper wire cut to length.
When soldering them, try to ensure they are held tightly
to the board to prevent rattling. Dabs of RTV or neutral cure
silicone under each one should help in that regard.
Next, fit REG7, the sole SMD regulator, while there is plenty
of room around it. Follow with the ten resistors in this section,
each being near one of the regulators. Then fit 1N4004 diodes
D22-D29. As before, watch their orientations.
Then install the six MKT capacitors, followed by the 12
polarised electrolytics. As usual, make sure their longer leads
Soldering tips
• Use a very fine tip on your soldering iron, the finest solder
you have, with gel or liquid flux and a magnifying lens.
• Stay calm. Remember that if you only solder down one pin
of each device at the start, you can easily melt this and move
things around to get better alignment.
• Then by soldering a second pin, you can lock the part in
place. Go easy on the solder and remember you can reflow
one pin if you need to nudge the part a bit.
• Use less solder than you think you need. You will be surprised!
go into the pads marked +. Keep in mind that they are not all
oriented the same way. Again, with the two 470µF capacitors,
they must be 25V-rated types, not 6.3V.
Finally, fit TO-220 package regulators REG3, REG4, REG6
and REG8. Three of these (REG3, REG4 and REG6) are mounted
on small heatsinks. In each case, place a lockwasher over a
6-10mm M3 machine screw shaft, followed by a flat washer.
Insert an insulating bush into the hole on the regulator tab,
then feed the machine screw through this.
Slide a TO-220 insulating washer over the screw shaft,
then feed the screw into the tapped hole on the heatsink. Do
the screw up loosely, then drop the regulator leads into the
PCB pads, while also lining up the heatsink posts with their
mounting holes.
Make sure the heatsink is pushed down fully and solder its
posts to their pads. You will need a hot iron to do this, and
it also helps to add a little flux paste to the area around the
bottom of the posts. Then hold the regulator vertical and do
up the machine screw tightly before soldering and trimming
the regulator leads.
Note that if you are using the recommended NE5532 op
amps, in theory, you could leave off the heatsinks for REG3
and REG4. But they would run hotter. We recommend that
you fit all three, just to be safe.
Testing the linear regulators
Reconnect the plugpack and measure the voltage at either end
of FB9, on the left side of the PCB. You should get a reading
in the range of 3.2-3.4V. Ours measured a touch over 3.4V –
this is OK since the rail is currently unloaded.
Measure either end of FB7 for +5V; this should read between 4.75 and 5.25V. Then measure the voltage on the tab
The completed project, albeit upside down! The main SuperCodec PCB ‘hangs’ off the rear panel with no connection at all
to the front panel – even the power LED shines through a hole in the panel. The daughter board (at left of main pic and inset
above) is the MCHStreamer USB to I2S interface which plugs into the two 12-pin sockets on the underside of the main PCB.
Practical Electronics | November | 2021
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of REG6, which is the +2.5V rail. This should give a
reading between 2.3V and 2.7V.
Next, check the voltages on the right-hand pads for
the two 10Ω resistors in the upper-right corner of the
board. The pad nearest the top edge of the board should
be −9V (−8V to −10.5V) while the one immediately
below should be +9V (+8V to +10.5V).
If there are any problems, check the plugpack output
voltage – is it working OK, or has it overloaded and
shut down? If it shut down, look for a short circuit on
the board. If you have not used the specified plugpack,
is that negative regulator overloading it on startup? Try
a beefier supply.
Also check that all the diodes and capacitors are the
right way around and all solder joints are good.
Once the power supplies are all up and running, you
are well on the way. We can now mount the remaining
SMDs without fear of damaging them.
Galvanic isolator and ASRCs
This section is in the lower left-hand corner of the PCB
(Fig.17). Start by loading all the surface-mount capacitors
in this section, then all the SMD resistors. The capacitors
will be unmarked; while the resistors will be marked with
codes indicating their values; you will need a magnifier to
read them. In all cases, it’s easiest to rely on what’s written on the packaging, and fit one set of values at a time.
Adding a little flux paste (or liquid flux) on each
SMD pad before placing the component will make
soldering easier.
With the capacitors and resistors in place, proceed to
solder IC6, IC7 and IC12. Note that pin 1 faces towards
the bottom of the board in each case. Check and doublecheck the pin 1 marking on top of the IC package before
soldering them, as they are difficult to remove. Again,
flux paste will make soldering these parts much easier.
Given the proximity of the pins on these ICs, it’s best
not to worry about bridging pins when soldering them.
Instead, check carefully after soldering using a magnifier, and use a dab of flux paste and some solder wick
to clean up any bridges which have formed.
If you are lucky, you will have a microscope; if not,
you can use a smartphone camera to zoom in close to
the soldered pins and take a photo. This is a good way
to check for hidden bridges between pins.
Next, mount the 4N28 and associated through-hole
resistors, plus transistor Q1 and reset chip IC13.
Finally, install the headers for the MiniDSP MCHStreamer which go on the back of the board. These
should be ESQT-106-03-F-D-360 elevated headers providing 10mm clearance, to ensure the MCHStreamer fits.
Testing this section
Follow the instructions in the text box below to install
the driver and get the MCHStreamer running. Once
you’ve connected it to your computer, check that it has
been detected by clicking on the volume control and Fig.17: the PCB overlay for the SuperCodec shows all components
checking that it comes up with Speakers (MCHStreamer in place. However, as discussed in the text, it’s best to assemble the
Multi Channels), as shown in that panel. Operating sys- board section-by-section, allowing you to test each on completion
tems other than Windows will use a different method. and if necessary, fix any errors as you go. This overlay does not
Once you’ve verified that it has been detected, unplug show the MCH daughter board, which plugs into the two header
it from the computer and then fit it into the two match- sockets (bottom left) on the underside of the main board.
ing sockets on the underside of the PCB. It should seat
If the MCHStreamer is already selected, then you’re all set.
firmly onto the connectors.
Power the sound card back up and connect the USB socket Otherwise, left-click on the caret (‘^’) to get a list of available
to your computer. You then need to make sure that the MCH- sound devices. You can then switch to the MCHStreamer.
Now play some music or another audio file. It does not
Streamer is selected as the current sound output.
To do this in Windows 10, left-click on the sound icon, matter what you choose, as we just want data to come out of
and you will get a pop-up window as shown in the panel. the MCHStreamer.
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Practical Electronics | November | 2021
will assist you in isolating power-related problems to a
small group of components. Also check for solder bridges,
bad solder joints (especially on SMD IC pins) and check
those capacitors.
Loading the DAC and ADC sections
These sections are in the top half of the board and include
all the remaining components. Start by fitting all the
remaining surface-mount capacitors. Make sure that the
two 2.7nF (2700pF) caps go where indicated as these are
critical to good performance.
There is also one SMD resistor remaining (220Ω) so install
that now. Then solder the ADC and DAC chips, IC1 and
IC2. Orient both with pin 1 towards the top of the board,
with the power supplies are at the bottom. Use lots of flux
paste, thin solder wire and tack down one corner to allow
you to align the IC before soldering the remaining pins.
Check there are no missed SMDs now, as after we load
the through-hole parts, it is harder to get the soldering
iron in there.
Now mount REG5, the LP2950-3.3V in a TO-92 package.
Follow with the seven ferrite beads left, FB1-FB7, then all
the rest of the through-hole resistors and diodes.
The diodes left are all BAT85s, but they don’t all face
in the same direction, so check the Fig.17 to make sure
they’re all installed with the correct orientation.
The seven op amps are next. They are all oriented with
pin 1 towards the upper right-hand corner of the board.
You can either solder sockets and then plug the ICs in,
or solder the ICs directly to the board (which will give
better reliability, but make it harder to swap them later).
Follow with all the MKT and ceramic capacitors, then
the electrolytics. As usual, be careful to insert the longer
leads of the latter into the pad nearest the + symbol, which
varies in orientation for each capacitor.
The 470µF capacitor below IC9 is the 6.3V-rated type,
to allow it to be closer to the chip, while the four 22µF
capacitors are non-polarised types. (You could use 47µF or
100µF NP capacitors, as we did in our prototype, although
we didn’t find this to give any benefits.)
Now fit LED1, again with its lens 10mm above the
PCB and with its anode to the pad marked ‘A’. Then fit
polarised headers CON4 and CON5, and the PCB assembly is complete.
Testing this section
Check that there are no missing parts on the board. If there
are, look them up and fit them. Also check your soldering
to make sure it’s all good, especially on the SMD ICs. It’s
best to clean flux residue off so you can get a good look
at the solder joints.
Now apply power, without the sound card plugged
into a PC. It is not even necessary that the MCHStreamer
is plugged in, but this does not matter as it is isolated
from the rest of the board!
Connect the ground of your DVM to a convenient
ground point. We soldered a PCB pin to a few of the
Here’s the matching PCB photo – there’s a mix of through-hole and larger GND vias; there is a convenient one just above
SMD components. You shouldn’t have a great deal of drama with the 3.3V regulator. But you can also just hold the black
the resistors and capacitors, but some of the SMD ICs have quite probe in one of those holes.
Apply power and board and re-check the 3.3V rail,
fine pin spacing so you’ll need to take your time with these. Any
solder bridges between pins must, of course, be removed.
the +5VA rail, the +2.5V rail and the ±9V rails, as before.
This is to make sure you haven’t introduced any short
Check that the collector of Q1 (the pin towards the bot- circuits across any of the rails.
tom of the PCB) goes high. Check for fixed-frequency square
Assuming these are OK, and there is no part emitting
waves on the test points labelled on the PCB: MCLK (25MHz), smoke or getting hot, we can proceed. If something is wrong,
BCLK_DAC (12.5MHz) and LRCLK_DAC (195.3125kHz).
follow the usual checks for solder bridges, especially on the
If you have trouble, check the power supplies. Anything odd
ADC and DAC where the pins are close to one another. Also
here needs to be tracked down. The individual power supplies check the component orientations.
Practical Electronics | November | 2021
23
You can solder fine-pitched SMDs with a standard iron.
Now it is time to get into some of the fun tests. Switch the
power off, plug the MCHStreamer into the sound card and the
PC, then plug its outputs into some sort of amplifier. Power
it back up and play some sound (eg, music). Then you can
check that you get appropriate sounds from the amp!
Alternatively, you may choose to put a scope on the
output(s) and look for the audio. Assuming that works,
connect a stereo RCA-RCA cable from the outputs to the
inputs, play some audio and then simultaneously make a
recording. Check that the recorded sound file matches the
playback audio.
If any of these tests fail, check the data paths from the
MCHStreamer to the DAC and ADC chips. This
is ideally done using a scope with its timebase
set to 50ns/division. Check the MCLK, LRCLK,
SDATA, BCLK and RESET lines.
If the RESET line is not high, the MCHStreamer
is probably not connected properly. Is its light
on? Why not?
Check the clock and data lines on the USB card
side of the galvanic isolators – they should be
there if they are on the PC side. If not, why not?
If you are lucky enough to own one, a PCB microscope
can help identify problems in soldering – or alternatively,
confirm you’ve done a great job! If you don’t own one, you
could try using the camera in your smartphone to take
close-up shots which you could then enlarge via your photoediting software to help you spot any ‘oopses’. Don’t have
photo-editing software? Try downloading GIMP (it’s free!).
ensure that the SuperCodec is held tightly against the rear
panel. This will minimise strain on the MCHStreamer connectors when power is being plugged in and out. If you have
foam tape, a thick layer of this along the edge of the PCB
would also work fine.
The SuperCodec slides into slots in the case and is held
tight by the rubber stopper at the front, and the MiniDSP
MCHStreamer, which is attached to the rear panel.
Final assembly
You need to make up some cables using the two polarised
header plugs and matching pins, two 30cm lengths of
Metalwork
If you are using the recommended case, the
Hammond 1455N2201, there is refreshingly little
metalwork to do. Cut and drill the front and rear
panels as shown in Fig.18.
The front panel has a single hole for the ADC Clip
LED. The rear panel has cutouts for the USB input,
power input, power LED and four RCA connectors.
Rectangular holes are always a nuisance to cut.
As these are small, we recommend marking the
outlines on the panel, then drilling a series of
small holes around the inside perimeter with a
1.5-2.5mm drill bit. Keep the holes close together
and err on the side of drilling well inside the
marked square, rather than touching the outline.
Once you have broken free the tab of aluminium
from the middle of the hole, use a square or triangular file to neaten the holes to the required
square. Touch up the edges with black paint or
at a pinch, a marker, to make this neat.
To finish the front panel, stick a small rubber
stopper on the front panel in a location that will
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Practical Electronics | November | 2021
A view of the board with the power supply sections
completely assemble and nothing else. This way, we can
check that all the supply rails are correct without risking
any damage to the expensive chips they will be powering.
figure-8 screened cable, the four RCA panel-mount connectors and some heatshrink tubing. The result is two cables,
each with two RCA connectors at one end and a four-pin
header plug at the other.
At the header ends, start by separating the two channels
of coax, then stripping 25mm of the outer sheath of each,
exposing the shield braid. Tease the inner conductor from
the braid, and strip the end by 5mm. Twist the braid wires
together into a neat bundle.
Next, cut two 20mm lengths of heatshrink, one around 3mm
diameter and one 5mm. Slide the 5mm piece over both the
shield braid and central conductor. Do not shrink this yet.
Slide the 3mm heatshrink over the braid; there ought
to be 4-5mm of wire protruding. Shrink this down. Slide
the 5mm heatshrink sleeve to cover about 3mm of the
junction where the braid and inner core separate, then
shrink it down.
Present the bare wires to a crimp pin. You need to trim off
excess braid wire, so that the strain relief crimp (at the back
of the pin) will go over the braid, with about 3mm of wire in
the main crimp as shown.
Fig.18 (opposite): drilling/cutting diagram for the rear and
front panels (most holes are on the rear panel with only
one LED hole requrired on the front) – it is available for
download from the November 2021 page of the PE website.
Above are the rear panels (yes, we made two prototypes!)
with masking tape holding down the panels and also
providing a handy means of marking out the holes required.
Practical Electronics | November | 2021
Test points are provided to help you verify correct operation.
Crimp the middle section using sharp-nosed pliers. Make
sure the crimping doesn’t cause the pin to splay out so wide
that it will no longer fit into the plastic block. Then add a tiny
amount of solder to the crimp, being careful not to allow it
to wick down to the connector spring. Then crimp the strain
relief onto the heatshrink around the braid.
Next, strip back 3mm from each of the inner conductors
and crimp and solder to another pin as above.
Now push the pins into the header plug. The shield braids
go into the middle two pins, with the left and right signals
on the outside. You will feel and/or hear a click when they
seat properly.
Then take the two pairs of RCA socket and mount them to
the rear panel using the supplied plastic insulating washers,
to isolate them entirely from the back panel.
As before, separate the twin coax cables into left and right
wires, and strip back 25mm of the outside insulation. Cut
two more pieces of 5mm and 3mm heatshrink and twist the
braids, insulate them and then shrink the braid and overall
sleeving, as with the header end. You can then solder the
input and output wires to the RCA connectors, as shown in
the photo above.
The two things to check for are that the input pair and output pair are wired to the same cables and that the left (white/
black) and right (red) sockets are wired to the appropriate pins
on those headers – see Fig.17. Check the orientation of your
polarised headers to determine which pin will go to the left
signals on the board, and which goes to the right.
You can make these checks most easily by plugging the
cables into the sockets on the board and then using a DMM
set to continuity mode. Probe from the centre of each RCA
connector to the pins on the headers (through the slots in the
plastic housing), to verify that each one goes where it should.
Mounting the USBStreamer
The USBStreamer needs to be isolated from the case of the
SuperCodec. This optimises the effectiveness of the galvanic
isolation and improves hum rejection.
This is achieved by using TO-220 bushes on the M3 machine
screws that attach the USBStreamer through the rear panel,
and placing fibre washers on the inside of the rear panel,
between it and the USB Streamer brackets.
See the photo overleaf, where you can see the insulating
washers under the screw heads on the rear panel.
This is required to prevent ground noise from the USBStreamer card being conducted through the case and injecting
itself into the very sensitive ADC stages.
While you’re doing this, something to note is that the
mounting lugs on our MCHStreamer board were not lined
up properly. We reckon this was due to sloppiness on the
part of whoever (or whichever robot) soldered the threaded
standoffs to the board. This can result in the MCHStreamer
sockets looking crooked on the rear panel.
25
After crimping and/or soldering the crimp pins to the end
of the wires, push them into the plastic housings and they
will click into place.
If, after mounting your board to the panel, it is noticeably
crooked, all you have to do is pack one of its mounting screws
on the inside of the panel with an extra fibre washer or two.
That should straighten it right up.
It’s also very important that you stick a 7.5-8mm tall rubber
foot on the bottom of the MCHStreamer board as shown in
our photos. As this board is only attached to the main board
via headers, and it’s only mechanically mounted at one end
(to the rear panel), it’s possible for its pins to lose contact
due to shock or vibration.
The rubber foot rests on the bottom of the case and holds
the far end of the MCHStreamer up so that the headers can’t
come out of their sockets.
When you slide the PCB into the case, the foot should
press against the bottom and provide a little extra resistance
to sliding the board in, but not so much that it becomes impossible. This is how you know that it’s providing enough
force to hold the boards together.
Grounding
If you want to get the 50Hz hum down below −120dB,
as we achieved in our prototype, Earthing is very important. To be honest, in testing this, we found that even the
slightest change in the configuration can cause changes
of 10dB or more. That just shows how difficult it is to
achieve such performance.
A 10nF capacitor between the input grounds and rear
panel earth lug minimises hum pickup.
In most tests of amplifiers, you will need the galvanic isolation that the system provides to measure really low noise
floors. Where super-low noise is critical, you might find with
some system configurations that the earth of the PC does need
to be tied to the device under test to eliminate induced 50Hz
signals being picked up. This will require experimentation
with your overall setup.
You should establish the noise floor with no signal to the
unit under test before running any tests.
You should have a 10nF MKT capacitor left over, which
was specified in the parts list (in part one) but not used on
the board. You should also have a 10mm M3 machine screw,
three locking washers, a solder lug and an M3 nut, again
specified in the parts list.
Cut a 6mm length of 3mm-diameter heatshrink, then mount
the M3 machine screw through the hole in the rear panel with
a locking washer either side. Place the solder lug on top, then
the third locking washer and finally the M3 nut. Do it up tight.
Put the 6mm heatshrink over the capacitor leg, and solder
this to the solder lug. Then solder the other lead of the capacitor to one of the shield braid wires of the output connectors.
Tip: if you envisage using this as a measurement system,
put a solder lug on the outside of the case as well. This can
use the same screw. As we found in our tests, access to the
unit’s ground can be useful in some cases to minimise overall
system noise. Adding this while building it will be a lot easier
than adding it later. Slide everything into the case once it is
all working, then mount the panels and you are set!
If you envisage this device being moved around a lot or
vibrated, then you might want to add a piece of Presspahn or
Elephantide as shown below-left. This is optional.
Using it
If you want to use the SuperCodec for playback, you can
use just about any audio software. But if you want to take
advantage of its full capabilities, you will need high-resolution
The pre-assembled USB Streamer PCB plugs into the two
12-pin header sockets on the underside of the PCB.
A piece of insulating material such as Presspahn, located
as shown here, will ensure the MCHStreamer is always
isolated from the case.
26
Here’s what the back panel of your SuperCodec should look
like when finished. Note the comments in the text re the
grounding/insulaton of the sockets to avoid ground loops.
Practical Electronics | November | 2021
Getting the USB interface up and running
First, you’ll need to install the driver on Windows or macOS. Log
onto the MiniDSP website with the password you used to buy the
MCHStreamer, and navigate to the download section. Download
the driver for the MHCStreamer. Follow the instructions to install
this from the MiniDSP website, which in summary are:
1. Plug the MHCStreamer module in via its USB cable. It does
not need to be plugged into the sound card PCB; it can just be on
your workbench (but make sure it’s on a non-conductive surface).
It is powered from the computer via the USB cable
2. Our Windows 10 PC popped up a window saying it was
‘setting up the MCH Streamer’, then a second window saying ‘the
MCHStreamer was ready to go’
3. Extract the contents of the ZIP file you downloaded from
their website
4. Navigate to the ‘Drv_DFU\WinDrv’ subdirectory and doubleclick on the installer, which in our case was named ‘miniDSP_
UAC2_v4.67.0_2019-08-15_setup.exe’
5. When asked if you want to allow the App to make changes,
click ‘Yes’
6. Follow the prompts in the installer, selecting defaults including file locations.
The SuperCodec should now be up and running.
To set the sampling rate, right-click the speaker icon in the
taskbar, usually in the bottom-right corner of the screen. Select
‘Open Sound Settings’ and check that the system has ‘Speakers
(USBStreamer Multi Channels)’ selected as the output device
(see below).
This should automatically be selected. If not, select it. Then
click on ‘Device Properties’ in blue, just below the device selection
pulldown box. In the new window that appears, look for ‘Additional
Device Properties’, again in blue. Click this.
In the pop-up window, go across to ‘Advanced’. Here you can
select your sampling rate, and also click a ‘Test’ button. We recommend selecting ‘24 bit, 192,000 Hz (Studio Quality)’. Then click
‘Apply’ down the bottom left.
While the download package includes the firmware, the MCHStreamer is shipped with the firmware already installed. This does
not need to be changed. If you have fiddled with this, you will
need to install the I2S_TOSLINK firmware. To do this, follow the
instructions in the manual.
Several other configurations will work for us, as all we need are
I2S channels 1 and 2 in and out on the header.
Once the drivers are installed and the MCHStreamer
is plugged into your PC via USB, it is set as the default
output device automatically.
If for some reason it isn’t, you can select it from the list
of available audio output devices by clicking the caret
on the right.
content such as 96kHz or 192kHz, 24-bit FLAC files, along
with a player that can properly decode such files.
For recording, we suggest that you try the free software
package called Audacity (www.audacityteam.org). It is available for Windows, macOS and Linux and can take advantage
of the Card’s full capabilities.
For audio analysis use, such as measuring distortion
(THD+N or THD), signal-to-noise ratios (SNRs), frequency
responses and so on, various packages are available. We use
audioTester (www.audiotester.de).
This is ‘shareware’ so you can download and install it for
free, but you can only use it for a limited time without paying for it. It only costs €39 or about £35 for the full version.
We recommend this software because it is easy to use and
has many comprehensive features that are ideal for testing
audio equipment. That includes a low-distortion sinewave
generator, spectral analysis with automatic display and
calculation of the signal level and total harmonic distortion
(THD) and much more.
Reproduced by arrangement with
SILICON CHIP magazine 2021.
www.siliconchip.com.au
Coming up: a balanced attenuator add-on
A section of Kapton tape on the USB socket ensures it can’t
short to any components on the main PCB.
Practical Electronics | November | 2021
Phil Prosser has designed an add-on board for this project which
adds balanced inputs and a switched attenuator with settings of
0dB, 10dB, 20dB and 40dB.
This add-on board greatly improves the flexibility of the SuperCodec when used as a measurement instrument, and only
slightly degrades its performance.
If you’d like to build this add-on board, go ahead and start
building the SuperCodec but don’t fit the headers for the MCHStreamer just yet, and don’t drill the case end panels either, as
both the MCHStreamer and the main PCB are mounted slightly
differently to make room for the add-on board.
The article describing this add-on board will be published in
the next two issues.
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