The γ1.5 miniature high resolution USB DAC + headphone amplifier
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News

  • Jan 29, 2015: γ1.5 circuit boards, ζ1 modules and precision CNC-machined/engraved front and rear panel sets are now available from AMB audio shop.
  • Custom-built, ready-to-use γ1.5s are available exclusively from MisterX (Marshall Wyant). Please contact him directly for details.

Overview

γ1.5 ("gamma one point five") is an audiophile-quality stereo asynchronous USB digital-to-analog converter (DAC) and headphone amplifier for portable, home and office use, supporting up to 24 bit and 192KHz sample rate. Designed to be housed in a very compact enclosure, its footprint is the size of a credit card, and about 0.9" (23mm) thick. Despite the small size, the selection of high-end parts and careful design resulted in uncompromising performance and sound quality. γ1.5 offers an affordable DIY alternative to costly commercial DAC/headphone amplifiers. Its headphone output drives low and high impedance headphones with ease, and can also be used as a line output. γ1.5 is ideal for computer and smartphone/tablet USB audio, and supports Linux, MacOSX, Windows, iOS and Android platforms.

In conjunction with an off-the-shelf enclosure solution and wire-free board mounting of all components, γ1.5 is relatively easy and inexpensive to build. There are some surface-mount parts, but most passive parts are through-hole.

γ1.5 is designed by AMB and MisterX with community input. See the History section for details.

Some photos of the γ1.5 (click to enlarge)

Basic feature set

  • Portable audiophile-quality USB DAC and headphone amplifier.
  • Powered from USB port.
  • Uses the ζ1 Audio Widget USB-I²S module.
  • Low-jitter asynchronous transfer mode.
  • USB Audio Class 1 and 2 support, the latter up to 24 bits, 192KHz sample rate.
  • High-end Wolfson WM8740 DAC.
  • Dual low jitter, low phase noise oscillators.
  • High-CMRR balanced-to-unbalanced converter & analog low-pass filter.
  • High output current headphone amp, for low and high impedance headphones.
  • Analog volume control, Mini-B USB connector, 3.5mm stereo headphone jack.
  • Small tactile switches for UAC1/UAC2 mode switching and for firmware upgrade mode.
  • DC coupled throughout: no coupling capacitors in the signal path.
  • Separate low noise, LDO voltage regulators for digital and analog circuitry.
  • Each power branch is additionally filtered by ferrite beads.
  • Ultra low noise and low distortion.
  • Hybrid through-hole and surface-mount (SMD) parts.
  • High quality FR-4 PCB with four copper layers.
  • Perfect fit into Hammond 1455C80x series aluminum extruded casing.
  • Special CNC-machined and engraved front and rear panel sets are offered.
  • See the Technical highlights section for further details.
  • Open source design with community participation. See the γ1.5 development thread in the AMB DIY audio forum.

What skills and tools are needed

You 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 parts), 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 AMB CNC-machined 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 γ1.5. If you don't thoroughly understand everything, please consider having someone more experienced to build it for you.

The scope of the γ1.5 project

The γ1.5 project is primarily centered around γ1.5 circuit board and the ζ1 Audio Widget USB-I²S module. You should also add a Hammond 1455C801 or 1455C802 enclosure. The circuit boards are designed to slide into these cases without additional mounting hardware.

Why not offer a full kit

AMB is not prepared to stock all the needed parts and offer them as a full kit. This DAC/headphone amplifier 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.

Why not offer the finished product

This is intended to be a project for DIYers, and AMB is not set up to manufacture completed units.

Professional builder

Inquire with the following professional builder if they would build you a completed γ1.5, in case you cannot build one yourself.

Where to get help

Be 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. Search the forums for an answer before asking a question. Your question may have already been asked and answered.


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