Portable SPDIF & analog input DAC and high performance headphone amp

This web page documents the development of this product.  This is a shipping commercial product; pricing approx $400, inquire for details.

Board is 4.5" x 2.75", 4 layer
Design timeframe: August 2005 - August 2006
Last webpage update: May 20, 2007

Top View:
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Bottom View:
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This product was developed to address the needs of high performance monitoring at on-location recording and to bring audiophile-grade headphone listening to the myriad of portable audio devices in the modern age.  With good headphones the improvements over the $4 headphone amplifiers found in most gear is amazing.

Basic features:


Creating products that are small sized, battery powerable, pro-audio / audiophile performance and sanely priced is no mean trick.  Careful board layout, 3 design iterations, and exhaustive testing are required.  Out-of-left-field problems like physical IC design bugs in the SPDIF receiver (not locking to single-speed rates if it was just running at quad), the DAC (not fully powering down when told to if it doesn't recieve clocks from serial audio in), and the first potentiometer used (manufacturing problem with the taper at full clockwise).  These issues were identified and fully resolved by firmware enhancements and switching manufacturers.

As a commercial product, I can't go into the specifics such as part #s and proprietary analog design details.  What can be said: there are 4 dc/dc converters with LDO and ferrite-bead post-regulation, a PIC microcontroller to run the show with software designed for it to run with low power, smart powering-down of digital stuff when in analog mode, turning off the Toslink input when a coax input is selected, etc.  Extensive use of film caps, 6 separate ground pours, careful trace layout, 18 different Audio Precision tests (on every board produced!) and even a gold-plated headphone jack are some of the details that went into producing this design.

The headphone amplifier is super-beefy as well as high fidelity.  The "R&D" prototype, made to verify manufacturer performance specifications and signal flow design has been running the 8-ohm studio monitor speakers I use for playing music on the computer (mostly my 600 CD collection FLAC encoded and the marvellous soma fm) all day most days for two years.  (I gotta get out more.)