If you have not built all of them, refer to each of these
project's websites for instructions, then return here to
integrate them into the γ3 DAC.
Before proceeding further, you should have also unit-tested
your σ11 and σ22 power supply boards to make sure
they are producing the correct output voltages.
The following sections are arranged in the recommended order-of-work.
Many of the photos and illustrations are mouse-clickable to display a
larger, clearer version.
All hardware listed on this page are in US/imperial sizes, the
Parts list shows Metric alternatives.
Several steps below require you to make wire harnesses to connect panel
components to Molex connectors on the backplane board. You should
measure the wire lengths so that they are consistent, and no
longer than is necessary for strain-free connection.
Do not remove the integrated circuits from their sealed packaging until
you are ready to solder them on the board. This is to protect them from
electrostatic discharge and moisture.
While you look at the board layout, please also take the time to
check the schematic diagram
and associate each part with their location in the circuit. While this
is not normally required to build a working unit, one of the benefits
of DIY is to learn about how the circuit works. Try to determine what
each part does and why the particular part or value is chosen. There
are many web resources to help you with this, including the
AMB DIY audio forum.
You will find the overall DIY experience more rewarding as a result.
Due to γ3's use of surface-mount devices (SMD),
you should have the following tools and supplies to help you work on
A good soldering iron with fine tip, preferably with adjustable
temperature. For example, a
Weller WLC100 with
ST6 tip. A more
deluxe soldering station such as the Weller
Weller WES51 or
Hakko FX888 is nice, but not necessary.
Liquid flux or flux pen for electronics soldering/rework.
Thin gauge solder, such as 0.025". Your choice of 60/40 or
63/37 tin/lead. Avoid silver solder as it requires high heat.
Lead-free solders also require higher heat and their durability is
still in question.
Fine tweezer with sharp points, such as those from
All parts should be mounted tight against the board for proper
Due to configurable input and output types, please take extra care
to mount the correct parts associated with each digital input
For the configuration jumpers JPn, you do not need to use
pin headers and jumper shunts, because they are usually set once and
never changed again. Just solder cut-off resistor leads across the
jumper pads where they should be shorted together.
If you're new at soldering surface-mount devices, please view the
following video, an excellent tutorial.
Surface Mount Soldering 101 by Curious Inventor
Do not mix up the SOT23 package logic chips and voltage regulators.
The markings on these devices are coded as follows:
U2, U4, U6, U8
Texas Instruments SN74LVC1G125DBV
Texas Instruments TPS79333DBV
Texas Instruments LP2985AIM5-3.3
Texas Instruments SN74LVC1G00DBV
Texas Instruments SN74LVC1G80DBV
Texas Instruments TPS22929DDBV
Note: The "_" character denotes a variance code or
for the manufacturing facility and could vary.
Clean both sides of the blank γ3 backplane board with paper towel and
isopropyl alcohol or electronics flux remover, then
solder the components to the board, beginning with the SMD components.
Apply liquid flux to the board solder pads, and
place the chip over the pads. Use the tweezers to pick and nudge
the chip until it is centered and aligned perfectly.
Be sure that the pin orientation or polarity is correct.
Most chips have a marking next to its pin 1. For SOIC packages,
the top edge of the package where pin 1 is located is
usually beveled. For SOT23 packages, pin 1 is at the lower left corner
if you are viewing the top of the package, with the markings oriented for
reading. For the Scientific Conversion SC947-02LF pulse transformer,
there is a small red dot near pin 1.
Press the tweezer tip on the top of the chip to keep it from shifting
while soldering. Apply only a tiny amount of solder to the tip
of your iron, and tack down one corner pin of the chip.
It helps to use a "wiping" motion of the tip on the pin and
pad. If necessary, make small adjustments while heating that pad and pin
again. If all is well, do the pin on the diagonally-opposite side.
Then, do the remaining pins one at a time, reflow any pin that needs
a bit of touch-up. If necessary, use the desoldering braid to remove
any excess solder, and be sure there are no solder bridges between the
Use your multimeter and check the resistance between each pin of the chip
and the pad to make sure you don't have a cold joint (i.e., your
meter should read close to zero ohms). Also check continuity between
adjacent pins for solder bridges (meter should read infinity, except
where the pins are supposed to be connected to each other, see the
schematic diagram for verification).
Now proceed to mount and solder the though-hole parts,
starting with the lowest profile parts and work up.
Since the γ3 circuit board holes are plated through,
through-hole parts should be soldered only on the bottom of the
board. Do not drill or enlarge the holes because that would damage
Make sure the correct part goes into each position on the circuit board.
Measure each resistor with your multimeter to ensure it's the proper value
before installing it.
Pay attention to the polarity of electrolytic and organic polymer
capacitors. The positive lead is usually the longer one.
Do not solder the γ24, α24 and ζ1 module plug-in
pin header strips yet. These will be done in a later step.
Inspect all solder connections carefully, using a magnifying glass,
to make sure there are no solder bridges or cold solder joints.
Use a multimeter in ohms scale to check for short circuits, and correct
any mistakes found.
2. Preparing the γ3 enclosure
This section assumes that the front and rear panels on your enclosures
are done (i.e., all holes and cutouts are drilled and the panel parts fit
You should drill holes on the bottom of the enclosure for mounting
the γ3 backplane board (11 places). The locations of these
holes should match the backplane board mounting hole locations as
shown in the illustration below. You can use the backplane board itself
as a template to mark the hole locations. Adjust the backplane
board position so that it's tight against the rear panel with no gap.
If you are using the ε31 bridge board, then the backplane
board should be centered between the left and right walls of the
specified Par-Metal enclosure.
The 1/4" #4-40 male-female standoffs
("STANDOFF1" in the Parts list)
are to be used to mount the backplane board. After you are done
drilling, install these standoffs in the holes, male side up,
and secure them with 1/4" #4-40 machine screws
on the bottom of the enclosure. Test fit the backplane board
and then set the board aside for further work.
If you are using the Par-Metal 2" enclosure, then you will
need to trim some material off the front and rear panel frames
in order for the LCD display and rear connectors to clear. It
also allows the backplane board to be mounted against the rear
panel without any gap. See the photos below. You can use a
nibbling tool, a flat file and a round file for
this purpose, or a powered grinding tool as you see fit. The
following photos illustrate the panel frames after modification:
You may install the rear panel jacks and power umbilical connector at
this time, but the wiring will be done in a later step.
When mounting RCA jacks, use their supplied washers to
electrically isolate them from the panel.
Do not install the front panel components (switch, LCD display,
IR receiver, potentiometer) yet.
3. Install the plug-in module standoffs
The "plug-in" modules refer to the γ24, α24
and ζ1 modules, which will be plugged into the
backplane board. The γ24 and α24s will be supported
by 7/16" #4-40 female-female threaded standoffs ("STANDOFF2"
Parts list) on the top side of the backplane board.
Install these standoffs in the locations shown below (12 places).
Secure the standoffs with 1/4" #4-40 machine screws on the bottom
of the board.
The ζ1 module does not use standoffs.
4. Install the pin headers and receptacles
Follow the directions below to install the pin headers (male) and
pin receptacles (female) that allows the various modules to
be plugged into the backplane board.
The pin headers for the γ24 and α24 boards should be
cut from the 36P pin header strip (as described in the
into the appropriate number of circuits for each location.
The ζ1 module will use the Sullins 2mm-pitch pin headers
The mated pin headers and receptables should be soldered at
the same time using the steps below to ensure correct alignment
and proper electrical contact. The following illustration
describes the steps to do so. A 2P pin header and 2P pin receptacle
is shown, but the same method applies regardless of the pin-count.
Before soldering, insert the male pin header into its associated
female pin receptacle.
Insert the mated pin header/receptacle assembly into the backplane board
solder pad holes, with the male pin headers on the bottom.
Align the plug-in board over the pin header/receptacle assembly until
the receptacle's solder tails protrudes through its solder pad holes.
For the γ24 and α24, secure the plug-in board by
fastening all of its screws into their corresponding standoffs,
and check the pin headers and receptacles for proper fitment again.
Solder the headers and receptacles on the bottom of the backplane board
as well as the top of the plug-in board.
Remove the screws and unplug the board.
The following illustration shows the locations where
the pin header/receptacle assemblies should be installed, and their
number of circuits. The red locations have 0.1" pitch, and the
male pin headers are taken from the 36P strip. The blue locations
have 2mm pitch and use the Sullins pin headers.
The following photo shows the bottom of the γ24, α24 and
ζ1 boards each with pin receptacles, ready for installation.
5. Install the Molex KK headers
Solder the Molex KK headers into the locations on the backplane board
as illustrated below.
Note the following:
The Molex KK header locations in green should be installed in all
Whether to install the Molex KK header locations in red depends on the
digital input and output configuration,
and whether unbalanced, balanced or both types of analog outputs
will be connected to rear panel jacks.
J12 and J13 are combined into one 4P Molex KK header.
J14 and J15 are combined into one 5P Molex KK header.
LJ5 and LJ6 are combined into one 4P Molex KK header.
6. Install backplane board
At this point you may clean the flux off the backplane board with
high-purity isopropyl alcohol or special electronics flux remover.
Then, install the backplane board into the chassis using #4-40
hex nuts (11 places). This is how things should look after
You may now install the plug-in modules (γ24, two α24s
and ζ1) now. Simply plug these modules into its respective
board connector pin headers. Install 1/4" #4-40 machine screws into the
standoffs for the γ24 and α24 boards to secure these boards.
7. Install front and rear panel components
Mount the LCD display, LCDuino-1 board and infrared receiver
Follow the steps below to mount the LCD display, LCDuino-1 and IR receiver.
It is assumed that you are using the custom fabricated front panel as
described in the Parts list section, or something
Install two 1/2" #4-40 male-female standoffs ("STANDOFF3"
in the parts list) on the back side of the LCD display board,
into two diagonally-opposite mounting holes. Secure the standoffs
with #4-40 hex nuts.
Install the front panel to the front panel frame. Place two
1/8" unthreaded spacers ("SPACER" in the parts list)
over the two diagonally-opposite LCD display mounting holes that
do not correspond to the standoffs in the previous step.
Fasten the LCD display to the front panel, through the spacers,
using two 1/4" #4-40 machine screws.
Using 22 AWG hookup wires, make a 3-wire harness and
strip the wire ends. Solder a 3P pin receptacle at one end
and tin the wires on the other end.
Use heat-shrink tubing to insulate the receptacle pins,
and solder the wires to the LCDuino-1 board. Shorten the leads
on the IR receiver and plug it into the receptacle.
Note: Make sure the IR receiver wiring is correct or you risk
damaging the IR receiver.
Carefully align the two 6P pin header on the LCDuino-1 board
to the matching receptacles on the LCD display, and plug
the LCDuino-1 board into the LCD display. Fasten the LCDuino-1
board to the standoffs with two 1/4" #4-40 machine screws.
Fabricate a mounting bracket for the IR receiver using thin sheet
aluminum, and mount the IR receiver to the front panel with
1/8" #4-40 machine screws. The "dome" on the
IR receiver should fit into the front panel hole.
Install the power/config pushbutton switch
Mount the switch to the front panel with the supplied
washer and nut.
Using 22 AWG hookup wires, make a 2-wire harness and strip
the wire ends.
On one end, crimp or solder Molex KK crimp terminals to the wires
and then insert them into a 2P Molex KK plug housing
until they lock.
On the other end, tin the wires and solder them to the
normally-open switch terminals.
Heat-shrink the switch solder joints.
Connect the Molex KK plug to J6 on the backplane board.
Here is a photo of the mounted switch with its wire harness:
Install the motorized potentiometer
Using 22 AWG hookup wires, make a 5-wire harness and strip
the wire ends. This wire harness should be long enough to
go from the mounted potentiometer to J9 on the LCDuino-1 board.
On one end, crimp or solder Molex KK crimp terminals to the
wires and then insert them into a 5P Molex KK plug housing
until they lock. On the other end, tin and solder the wires to the
motorized potentiometer. Heat-shrink the potentiometer
solder joints. The illustrations below illustrates the
connections for the Alps RK16812MG099 potentiometer.
Mount the potentiometer to the front panel with the supplied
washer and nut.
Connect the potentiometer Molex KK wire harness to J9 on
the LCDuino-1 board.
Note: J7 and LJ9 on the backplane board are unused.
Install rear panel jack harnesses
If you haven't already done so, mount the input and output jacks
on the rear panel. RCA and BNC jacks should be installed with
their insulator washers and nuts, if necessary.
For each digital input and output configured as AES/EBU or Coaxial,
and for each left and right channel unbalanced analog output,
make a 2-wire harness using 22 AWG hookup wires.
For each balanced analog output, make a 3-wire harness. Strip
all wire ends.
On one end, crimp or solder Molex KK crimp terminals to the wires
and then insert them into a Molex KK plug housing
until they lock. On the other end, tin the wires and solder them
to the jacks according to the
Pin 1 of each AES/EBU digital input should be connected to the
chassis. On the recommended Neutrik XLR female panel connector,
there is a "body" solder tab that could be
bent and soldered to the pin 1 solder cup. When the jack is
mounted on the panel, it will automatically make the chassis
connection. This is shown in the third photo below.
Install power umbilical connector harness
The power umbilical connector has eight circuits that should
be split into four groups: LVDD, SSRTRIG, GVDD, AVDD/AVSS.
These correspond to J12, J13, J14 and J15, respectively.
However, J12+J13 are combined into a single 5P Molex plug,
and J14+J15 are combined into a single 5P Molex plug. See the
Parts list and
Power supply schematic diagram
The schematic diagram also shows the Conxall Mini-Con-X 8P circular
locking connector (as listed in the Parts list) pin assignment as
used on AMB's reference build.
These wiring harnesses should be long enough to run from the
mounted circular connector to their destination J12-J15 connectors
on the backplane board.
Make the two wire harnesses.
Strip and tin both ends on each wire, and crimp or solder
Molex KK crimp terminals to one end of the wires.
Insert the crimp terminals into the proper slots
of each Molex plug housings until they lock into place.
Solder the other end of each wire to the respective pin of
the umbilical panel connector, use some heat shrink tubing at
the end of these wires to prevent short circuits.
Each completed harness should then be plugged into its corresponding
Molex KK pin header on the backplane board.
8. Build the LCDuino-1 Molex harnesses
The LCDuino-1 needs to be connected to the backplane board via
one of the following two options:
Use wire harnesses with Molex KK plugs.
Use the ε31 bridge board (only applicable when you
have the same enclosure, LCD screen location, backplane board
mounting location and standoff height as AMB's reference γ3).
This section assumes option 1. For option 2, please see the
You need to make six wire harnesses, each one terminated with
Molex KK plugs on both ends. The harnesses are described in the
table as follows:
# Circuits (LCDuino-1 side)
# Circuits (backplane side)
The pin assignments of these harnesses are all "straight-through"
(i.e., pin 1 goes to pin 1, etc.). The only exception is
the _Dn harnesses, which do not have pin numbers on the
LCDuino-1 side. Just make sure you connect them so that the
same _Dn numbers get connected on both ends.
Cut the wires according to the table above. Use 22AWG hookup wire.
Strip and tin both wire ends, and crimp or solder Molex KK crimp
terminals to the wires.
Insert wires into the proper slots of each Molex plug housing until
they lock into place.
Each completed harness should then be plugged into its corresponding
The _Dn harnesses connect to standard pin headers rather
than Molex KK pin headers on the LCDuino-1, therefore they do not
have polarity indication. Be mindful of the plug orientation.
Also, the connector does not lock, but pin/receptacle spring resistance
and cable tension should be enough to hold them in place.
Note: LJ3 is unused on the backplane board.
9. Mount the front and rear panels to chassis
The front and rear panels are now ready to be mounted to the
Mount the front and rear panel/frame assemblies to the chassis
bottom plate (for the Par-Metal cases, use four 3/8" #6-32
machine screws for each enclosure).
Plug in the Molex KK harnesses from the LCDuino-1 and panel components
to the corresponding Molex KK headers on the backplane board.
Plug in the six Molex KK harnesses that connect the LCDuino-1 module to
Plug in the power/config pushbutton switch Molex KK harness
to the backplane.
10. Build the power supply chassis
Mount the σ11 and σ22 boards in the power supply chassis
using 7/16" tall #4-40 standoffs ("STANDOFF4")
and machine screws (12 places).
Mount the power transformers and solid state relay into the
power supply chassis, install the IEC power entry module and the
power umbilical connector on the rear panel, and install the LED
on the front panel.
Wire up the box according to the schematic diagram shown in the
Power supplies section.
For the umbilical connector, use the same instructions and
pin assignments as the one in the main DAC chassis.
Note that the transformer primaries are to be wired differently
depending on your AC mains voltage. Use insulated FastOn connectors
for the AC mains connections at the IEC module, or use heat-shrink
tubing to insulate them. Use heat shrink tubing to insulate the
power umbilical panel connector solder joints.
Double check your wiring for errors.
Mount the front and rear panels on the chassis base.
Install the fuse in the IEC module.
11. Build the power umbilical cable
Using 22 AWG stranded hookup wires, make a 8-conductor cable to
your desired length. Strip and tin the wire ends.
Cut the protective braided sleeving to the appropriate length,
and run the wires through it.
Assemble the cable-mount connectors and solder the wires, making sure
that the pin assignments match on both ends. If you are using the
Switchcraft/Conxall Mini-Con-X locking circular connector
as listed in the Parts list, please refer to the
cable assembly instructions.
Make sure that there is good strain-relief for the wires in the
connectors. A large heat-shrink tubing at the end of each cable
connector is also recommended.
The basic γ3 platform is now done. Install the
rubber feet on both enclosures.
Check your work thoroughly, then proceed to the
Initial check section to continue the
bring-up of the system.