The table below is a complete parts list for the γ2.
See the sections below for specific parts recommendations and
options. For parts not offered by
AMB audio shop,
Mouser,
Digi-Key,
Newark,
Farnell,
RS Components
or another vendor's stock numbers for the recommended parts are listed
for your convenience. Part IDs shown in parentheses "()"
are alternates. Additional alternative parts are listed in the
Parts selection guide section below.
Part ID
Description
Mouser #
Digi-Key #
Farnell #
RS #
Notes
Circuit board
PCB, L1, L2, L3, L4, L5, J4, J5
γ2 PCB (includes five ferrite beads and one SIP-9 pin header)
See the parts list table above, which refer to specific notes here.
Install U6 only if you are using a WM8740 for U5.
Install U4 if you want the upsampling feature.
If U4 is not installed, then also omit U3, X1, R1, C7, C8, and
install jumpers JP2-[1-4].
AD8656 preferred for driving headphones directly.
Crystek, EuroQuartz and Aker are SMD, with slightly better specs.
Abracon is through hole.
SW1 and SW2 should not be installed if U5 is a WM8740 --
Short the FSEL and ACLIP pads to GND (see PCB silkscreen at the
SW1 and SW2 locations).
If you use the "break apart" style of pin headers and
receptacles, only one of each type is enough for all positions.
J3 must be omitted if the matching γ1 is a
Lite (B) configuration. For γ1 Full (A), USB-to-I²S (D),
S/PDIF-only (E) or Full++ (F) configurations,
also install a 1P long header pin into γ1's JP1D pin 2.
Install this jumper if γ1 is a "Lite" configuration.
You can simply use a resistor lead cutoff.
These jumpers should only be installed if U4 is not populated.
470µF should be used if driving headphones directly.
You may alternatively replace γ1's C24D and C25D with 470µF
units and use that section to drive headphones.
Parts selection guide
Due to the tight spacing within the enclosure, and to ensure proper
fit when the γ1 and γ2 boards are plugged into each other,
please observe the following recommendations. Do not use oversized
parts or mount parts in a manner that was not intended.
Do not change part values unless you know what you're doing.
All parts are carefully selected for optimum operation.
Resistors
All discrete resistors (except the resistor networks R1 and R2)
are miniature through-hole axial-lead types with a body length no longer
than about 4mm (the recommended Xicon, Panasonic and Multicomp resistors
are 3.5mm or 3.2mm), and no wider than 1.9mm. Metal film 1% resistors
are recommended for their thermal stability.
There are five types of capacitors used in the γ2:
conductive polymer electrolytic, audio-grade electrolytic,
metallized polyester, polypropylene film and
multi-layer ceramic.
C3 and C6 are conductive polymer electrolytic type for
their ultra low ESR characteristics. They are through-hole with radial
leads, 2.5mm lead-pitch, a maximum diameter of 6.3mm and a maximum
height of 12.5mm.
C11, C13, C20 and C26 are "audio grade" electrolytic capacitors.
They are through-hole with radial leads, 2mm or 2.5mm lead pitch,
a maximum diameter of 6.3mm and a maximum height of 12.5mm.
C11 and C13 are the WM874x DAC's mid-rail decoupling capacitors, and should
have the specified capacitance.
C20 and C26 are the DAC's analog output coupling capacitors, and are
bypassed by C19 and C25, respectively. See the metallized polyester
capacitor descriptions below for C20/C26 options. If you plan to
drive headphones directly from the γ2, then you should use
Nichicon KW or FW 470µF 6.3V or 10V capacitors to avoid
low-frequency roll-off.
Note that some of these "for audio" electrolytic capacitors
are non-polarized.
C19 and C25 are through-hole, radial-lead 1µF
"box"-style metallized polyester capacitors
with a lead spacing of 5mm. You may use MKT or MKS types
(or metallized polypropylene (MKP) in a lower capacitance,
but be sure that the footprint is no larger than 7.5mm x 5.5mm
and the maximum height is 12.5mm.
C19 and C25 are "bypass" capacitors for the C20 and C26
audio-grade electrolytic output coupling capacitors. Depending
on your preference, you may omit C19/C25 and run C20/C26 unbypassed,
or you may omit C20/C26 and run C19/C25 alone (but increase
their capacitance of C19/C25 to 3.3µF or higher to avoid
low-frequency rolloff and phase shift within the audio band).
If you choose the latter option, the Wima MKS 3.3µF 50V or
4.7µF 16V capacitors are the only known ones that would fit.
C15-C18 and C21-C24 are through-hole, radial-lead polypropylene film
or metallized polypropylene capacitors for the analog low-pass filter. Their
lead spacing is 5mm and the footprint should be no larger than 7.5mm x 4.5mm,
with a maximum height of 6mm. 5% tolerance or better is recommended for
accurate filter response.
All remaining capacitors are multi-layer ceramic type, with through-hole,
radial-leads and 2.5mm lead-spacing. Some capacitors have 2.5mm pitch
leads but come pre-bent to 5mm, you must straighten them to fit the board.
All multi-layer ceramic capacitors are X7R grade. Do not use Z5U,
Y5V or other lower grades.
L1 - L5: Panasonic
EXC-ELSA35 (included with the γ2 PCB).
Integrated circuits
The integrated circuits in the parts list table above should be used,
with alternatives as specified below. Some ICs come in several package
styles, be sure to use the correct ones that the board is designed for.
You may use either the LP2985 series or the TPS793xx series LDO voltage
regulators for U1 and U2, as shown in the parts list table above.
For U3 and U6, you may use MCP100 or DS1818 in TO-92 package. Each of
these come in several "threshold voltage" variants. It is
recommended that you use the 3.15V or 3.00V versions if available
(see their datasheets for the meaning of the part number suffix).
Note that U6 should be installed only if you are using WM8740 for U5.
You may use either the SRC4192 or the AD1896 asynchronous sample
rate converter for U4 as shown in the parts list table above. SRC4192
has somewhat superior specifications.
The default U5 stereo DAC chip is Wolfson WM8741GEDS/V. The
WM8742GEDS/V is equivalent, except the S/N performance is 2dB less.
The WM8740SEDS costs the least, and is the previous-generation
top DAC from Wolfson, but its performance has been bested by the
WM8741 and WM8742. Also, WM8740 lacks the switchable digital filters
and anti-clipping mode features. See the parts list table above.
U7 should be either a OPA2365AID or AD8656ARZ. These two were chosen
for their stringent rail-to-rail swing characteristics, low-noise,
low distortion and high CMRR performance. Do not substitute
with other opamps. OPA2365 is recommended for line-level use
while AD8656 is recommended if you plan to drive headphones directly.
Box Enclosures
B2-080 anodized with aluminum end-panels
Add the following suffix to specify the color:
BK - black
BL - blue
GD - gold
GR - green
RD - red
SI - silver
Box enclosures are available from
Newark,
Farnell and
RS Components.
A precision-drilled, engraved aluminum
for the γ2 + γ1 Full++ (F) combination
is available from AMB audio shop. Use these for ease-of-build,
upgraded appearance, and to assure a perfect fit. The
γ2s shown in the Overview section
are equipped with these panels.
