The γ1 modular miniature DAC

Technical Highlights

Ultra-compact, Versatile power, High-performance

  • The γ1 is almost the same size as a credit card, and about 0.9" (23mm) thick. The diminutive dimensions makes the DAC very portable and uses minimum desk/shelf space.
  • The extruded aluminum Hammond 1455C80x case, available in silver, black or blue anodized finishes, is attractive and sturdy.
  • The γ1 "full++" configuration uses the extruded aluminum Box Enclosures B2-080 case, available in a variety of colors.
  • Auto-sensing USB power or external power (via regulated 5V AC adapter).
  • The USB, digital and analog section power supply rails are each independently regulated by separate high-performance Linear LDO voltage regulators.
  • Ferrite beads and liberal use of decoupling capacitors further assure clean, low-impedance supply rails.
  • Transformer coupling of coaxial S/PDIF input and output for true galvanic isolation and improved CMRR -- usually found only in top-tier pro-grade equipment (rarely in consumer-grade).
  • Analog output taken directly from the voltage-output Wolfson DAC -- no I/V stage or opamps.
  • The Wolfson DAC is operated in "high performance mode" which increases its internal analog output stage bias, lowering distortion and improving S/N ratio.
  • Big, high-end sonics from a tiny package -- the γ1 is carefully designed for excellent performance, rivaling DACs many times its size and cost.

Modular, Full-featured

The USB and DAC boards can be used independently or mated together for the full feature set. Additionally, each board can be populated to various configurations. This results in five main build options:
  • A: Full configuration (USB board configured for S/PDIF format output, the DAC board fully populated with coax and optical inputs, all inputs selectable by front panel selector switch).
  • B: Lite configuration (USB board configured for I²S format output, no coax or optical S/PDIF inputs, no input selector switch).
  • C: USB-to-S/PDIF converter, no DAC board.
  • D: USB-to-I²S converter, no DAC board.
  • E: S/PDIF DAC only, no USB board (coax and optical S/PDIF inputs, selectable by front panel switch).
  • F: Full++ configuration (combination of A and C)

Integrated circuit complement

Some of these are optional depending on the desired build configuration (also see the circuit description in the Schematic diagram section).
  • Texas Instruments/Burr-Brown PCM2707 - USB interface and conversion to either S/PDIF or I²S
  • Cirrus Logic CS8416 - 24-bit 192KHz S/PDIF input multiplexer and receiver, low-jitter clock recovery and other functions
  • Wolfson WM8501 or WM8759 - 24-bit 192KHz high performance stereo DAC
  • Toshiba TORX147PL - S/PDIF fiber-optic receiver module
  • Toshiba TOTX147PL - S/PDIF fiber-optic transmitter module
  • Murata DA101C, Pulse PE-65612, Newava S22083 or S22133 - pulse transformer for coax S/PDIF input and output coupling and galvanic isolation
  • Texas Instruments TPS2115A - auto-switching power multiplexer for auto-sensing/switching between USB and external power
  • Microchip MCP100, MCP101 or Maxim/Dallas DS1818, DS1817 - reset manager chips for power-up sequencing
  • Texas Instruments TPS79333, TPS793475, LP2985AIM5-3.3, LP2985AIM5-4.5 - LDO voltage regulators for independent USB section, DAC digital and DAC analog supplies.
  • Texas Instruments SN74AHC1G02 and SN74AHC1G08 - Logic gates for status LED control and USB D+ line pullup functions.

Designed to be easy to build

  • A specific target case, DC power jack, input and output jacks, switch and other parts make this a highly integrated design.
  • All parts are through-hole except for the integrated circuits, minimizing the number of SMD parts and making the γ1 easy to solder and assemble.
  • For the surface-mount chips, the widest pin-pitch parts were selected where available, to make them easier to solder.
  • All parts are board-mounted, there are no wires to connect.
  • There are no trimpots to adjust after assembly.
  • All parts are easy to obtain (from AMB audio shop and from various online vendors, see the Parts list section).

High quality circuit board

  • Both the USB and DAC boards are glass epoxy 3.1375"x1.9875" printed circuit board, double-layer with plated-through holes, silkscreen and solder mask.
  • The two boards are supplied as a panelized "board set", grooved for easy separation into the two individual boards.
  • The layout of all parts and traces have been carefully considered for maximum performance.
  • Double low-impedance ground planes are employed, with particular attention paid to make the top layer ground plane as contiguous as possible to minimize current loops.
  • A strip of the ground plane is exposed along each side (both top and bottom), allowing the DAC's signal ground to be electrically connected to the case (via the board slots) without the need to add any wires. The grounded case improves RFI shielding without additional wiring.
  • The boards are designed to slide perfectly into a Hammond 1455C80x series extruded enclosure, making the casing of this DAC very easy.
  • The γ1 "full++" configuration uses the Box Enclosures B2-080 series extruded enclosure.

A 3D rendering of a partially-populated γ1 circuit board set.

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