Overviewγ2 (gamma2) is an extension and upgrade to the γ1 DIY stereo digital-to-analog converter (DAC). It builds on γ1's modular idea, and pushes the concept far into the high-end. Designed for the compact, attractive and sturdy Box Enclosures B2-080 series extruded aluminum casing, γ2's tightly integrated packaging makes it ideal for home and portable use, such as computer audio, CD/DVD players and digital media players.
The γ1 and γ2 boards plug into each other to form a two-board "sandwich". γ1 provides USB and S/PDIF receiver functionality and feeds the I²S digital audio datastream to the γ2. γ1 also supplies the raw 5V DC power to the γ2, which is then regulated locally on the γ2 board.
The γ1 Full++ (F) configuration is most easily upgraded to γ2, as it uses the same enclosure. The γ1 Full (A), Lite (B), USB-to-I²S (D) and S/PDIF-only (E) configurations may also be upgraded to γ2 by joining the two γ1 board sections back together and changing the enclosure. The only incompatible γ1 configuration is USB-to-S/PDIF (C), because it does not produce an I²S output. See the γ1 website about its various configurations and options.
γ2 could also used standalone as an upgrade DAC for any device that already has an I²S bus (e.g., A CD player or digital media player). Simply connect the I²S bus to the γ2 board and hook up a 5V DC power supply. See the instructions section for details.
On the γ2 board, the digital audio stream is upsampled to 24-bit 96KHz by an asynchronous sample rate converter (ASRC) and then converted to analog with Wolfson's top-of-the-line ΔΣ oversampling DAC chip. An onboard ultra-low jitter oscillator provides the master clock for the ASRC and DAC chips. A high-performance analog output stage serves as a balanced-unbalanced converter, low-pass filter and line-drive buffer.
For the cost-conscious builder, the ASRC chip and onboard oscillator may be omitted and bypassed with jumpers. They can be populated later (and jumpers removed) as funds allow. Without the ASRC, no upsampling will occur.
A front panel switch selects between linear phase brickwall, minimum phase slow-rolloff, and linear phase slow-rolloff digital filter modes, allowing the user to choose the performance characteristics on-the-fly. Another front panel switch enables an anti-clipping mode.
A rail-to-rail, low-noise, precision CMOS dual opamp implements balanced-to-unbalanced conversion, 100KHz analog low pass filtration and output buffering. The low output impedance and high output current capability allows a long interconnect cable to be used without degradation. It could even directly drive low-impedance headphones (AD8656).
With an off-the-shelf enclosure solution and wire-free board mounting of all components, γ2 is relatively easy and inexpensive to build. The only surface-mount parts are the integrated circuits, all other parts are through-hole. See the Tech highlights and Parts list sections for details.
γ2 is designed by AMB and MisterX with community input. See the History section for details.
Basic feature set
What skills and tools are neededYou should know how to read a schematic diagram and correlate it to the circuit board layout, identify electronic parts and their pin-outs, have decent soldering skill, and be proficient with a multimeter. You need at least a basic set of tools for electronics work, such as a good soldering iron (with a fine tip) and accessories, screw drivers, needle nose plier, diagonal cutter, a sharp tweezer (for positioning the SMD integrated circuits), etc. For the front and rear panels, you will also need to be able to accurately drill the holes needed for the input, output and DC power jacks, etc (unless you opted for the pre-drilled and engraved panel set).
To obtain the blank printed circuit board and some related parts, visit the AMB audio shop. Other parts are available from online vendors. See the Parts list section.
Please be sure to read every section of this site carefully before attempting to build the γ1 DAC. If you don't thoroughly understand everything, please consider having someone more experienced to build the DAC for you.
The scope of the γ2 projectThe γ2 project is primarily centered around the γ2 board. You will also need to build a γ1 to use with the γ2. You also need a Box Enclosures B2-080 series case. The γ2 and γ1 circuit board assembly is designed to slide into this case without additional mounting hardware.
Why not offer a full kitAMB is not prepared to stock all the needed parts and offer them as a full kit. This DAC is AMB's contribution to the DIY community rather than a for-profit product, AMB cannot assume the commercial support role that might be implicit with a full kit. However, to make sourcing parts easier, AMB includes the the ferrite beads and pin headers (for use as USB and DAC board interconnect) with each board set. Several other related parts are also available from AMB.
Why not offer completed DACsThis is intended to be a project for DIYers, and AMB is not set up to manufacture completed DACs.
Professional builderInquire with the follow professional builder if they would build you a completed γ2 DAC, in case you cannot build one yourself.
Where to get helpBe sure you read all the information at this site. If you cannot find an answer to a question, or encounter a problem you cannot solve, the best place to get support is the AMB DIY audio forum or the DIY forums at head-fi.org and headwize.com. Search the forums for an answer before asking a question. Your question may have already been asked and answered.
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