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Linux-powered CD player attempts audio perfection

Mar 22, 2013 — by Rick Lehrbaum 5,833 views

Parasound, a purveyor of fanatically high-end consumer audio equipment, has introduced a CD player that’s controlled by an internal Mini-ITX computer running embedded Linux. Using a CD-ROM drive for playing CDs, the “Halo CD 1” sucks in the CD’s contents at 4x normal speed, giving its CPU time to detect and eliminate disc errors before outputting near-perfect audio.

By reading data from the disc at four times the speed of a conventional CD player, the device’s embedded Linux computer can read each section of the disc multiple times, checking for discrepancies between the reads. When differences are detected, the sections are read again “as many times as needed to significantly reduce errors and, accordingly, [to eliminate] the negative effects of error concealment.”

The result, according to Parasound, is a “nearly bit-perfect data stream.”


Parasound Halo CD 1 front view
(click image to enlarge)

Some key features of the Halo CD 1 include…

  • User choice of an op-amp or discrete analog output stage
  • 44.1 kHz CD data is up-sampled to 352.8 kHz by an 8x interpolator
  • Six layer DAC board for lower noise and point of use power delivery
  • High performance, jitter-resistant Analog Devices AD1853 DAC IC
  • Ultra-quiet National Semiconductor LME49990 audio op-amps
  • 0 or 180 degrees absolute polarity selection by remote control
  • Choice of silent or audible fast forward or fast back
  • Unbalanced RCA and balanced XLR outputs
  • Optical, coax, and BNC digital outputs
  • Full-function remote control

You can see the CD 1’s rear panel connections in the photo below.

Halo CD 1 rear panel
(click image to enlarge)

Parasound says the device meets the following audio specs:

  • Frequency response: 20 Hz to 20 kHz, +0/-.05 dB
  • THD distortion: < 0.06% at 1 kHz
  • S/N Ratio: > 108 dB, IHF A-weighted
  • Crosstalk: > 77 dB at 20 kHz
  • Max. output level unbalanced: 2.0 Volts
  • Max. output level balanced: 4.0 Volts
  • Output impedance unbalanced: 100 Ohms
  • Output impedance balanced: 200 Ohms

The Halo CD 1 typically consumes 45W when active, and 0.5W in standby mode. Its horizontal dimensions are 17.3 x 13.9 inches and its height is either 4.1 or 3.5 inches, depending on whether its feet are present or removed.

Under the hood

Here’s a look inside the Halo CD 1, showing its Mini-ITX motherboard and other components:

Halo CD 1 internals, showing its Mini-ITX computer, etc.
(click image to enlarge)

Note how aluminum partitions provide electromagnetic isolation between its internal subsystems.


Parasound developed the Halo CD 1 through a collaboration with Holm Acoustics. An interesting technical whitepaper describes how the CD 1 works its magic. Basically…

    “The CD 1 reads a CD multiple times before committing data to an enormous memory buffer stored in RAM,” continues the explanation. “Every data sector is initially read twice and the two reads are compared. When the two reads match it is because no bit errors were detected and that is accumulated in the buffer memory. When the two reads do not match it is because an error has been detected. That sector is then read repeatedly until good data is obtained. If the maximum repeat read threshold is reached and the 30 seconds buffer is about to run out, the system switches to its pre-interpolation analysis mode. Data reading is then moved forward by only one sample at a time until the bad fragment is isolated. This process almost always results in error-free data. When interpolation techniques are needed, they are confined to the single small bad fragment, thereby minimizing their negative sonic side-effects.”

Regarding the device’s use of embedded Linux, the whitepaper explains that “the Linux operating system is bulletproof and there are no other programs, so there is little likelihood of it freezing or crashing, as with computers running Microsoft Windows or Apple OS.”

Further information

The Parasound Halo CD 1 CD-player comes in silver and black, and is priced at $4,500. For more information, visit Parasound’s website. The device’s technical whitepaper is available for download here (pdf file).

(advertise here)

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3 responses to “Linux-powered CD player attempts audio perfection”

  1. Blade says:

    …so it’s a $100 computer, with a $10 CD-ROM drive, and a really high end sound card. So, like $400 of parts, and possibly some custom software, although I think that it’s standard for most CD software these days to be able to read ahead and error correct.

  2. p-dawg says:

    Hahaahahah. Anyone who spends their hard-earned cash on this deserved to be parted from their money.

  3. Integration Guy says:

    The company I work for does high end installs for people with so much money they really seem to be unsure how to spend it. Celebrities, Movie Stars, Rock Stars, Fortune 500 Execs, Politicians and just very, very wealthy people. Our jobs typically include a home automation system like Savant or Crestron, distributed audio through out the home, in wall touch screens like something out of Star Trek and an equipment room with multiple eight foot racks housing the brains for all this stuff.

    These are the type of projects this CD player is aimed at.

    Interesting fact, we have not installed a new CD player in well over a year for any of these jobs. Most continue to use their old unit and, when it dies, they don’t replace it with a CD player. Or they just pull it from the rack to make room and throw it away. Instead CDs they use a media server that access all of their music stored on hard drives or from their iTunes account or they just use AirPlay with their iPhones.

    The audio CD is all but dead technology, at any price. At this price? Wow.

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