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Berkeley Audio Design Alpha DAC Reference Series 2

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An absolute reference DAC.

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The Alpha DAC Reference Series embodies everything we know about digital to analog conversion taken to an unprecedented level – a level that requires new design concepts and new components at the edge of what is possible. The result is an immediacy and presence of music reproduction that is simply real.

We literally designed the Reference Series before it was possible to build it. Almost three years in development, the Alpha DAC Reference Series uses components designed to our specifications that previously were not commercially available. Several suppliers were not able to meet our requirements which delayed the release of the Reference Series by more than a year. But those obstacles were overcome and now the Alpha DAC Reference Series is a reality.

The presence and sonic reality of the Reference Series is the result of digital to analog conversion at a new level of accuracy made possible by tremendous electrical and mechanical noise isolation coupled with extreme time domain stability. Ceramic aerospace circuit board materials are used in all critical areas and the enclosure is carefully engineered to minimize electrical noise and maximize mechanical and thermal stability. The Reference Series weighs 30 pounds and the entire enclosure is precision machined from solid billet 6061-T6 aluminum alloy.

A new high output metal IR remote control with direct input source selection is provided with the Reference Series.

Careful consideration was also given to providing the highest possible fidelity reproduction of DSD files by the Alpha DAC Reference Series. 99+% of modern DAC’s, including the Alpha DAC Reference Series, use multi-bit D/A converters because they provide better performance than 1-bit converters – even DAC’s who advertise “native” DSD compatibility. So, at some point, the 1-bit DSD stream must be converted to multi-bit for all of those DAC’s.

We could, like many other manufacturers, convert 1-bit DSD to multi-bit within the Alpha DAC Reference Series and show “DSD” in the front panel display. That would be the easiest approach from a marketing standpoint and would also be very simple and low in cost to implement. But that approach would also mean increasing the amount of processing in the DAC during playback which would degrade audio quality, and audio quality is the reason the Alpha DAC Reference Series exists.

Fortunately, virtually all reproduction of DSD files using external DAC’s is with a computer based music server as the source. If 1-bit DSD to multi-bit conversion is done first in the computer it can be performed with extremely high precision and superior filtering that preserves all of the content of the DSD file. Computer DSD to multi-bit conversion can be at least as good as that performed in a DAC and without adding processing noise near or in the D/A converter chip. Also, conversion of DSD to 176.4 kHz, 24 bit AIFF or WAV files can be done ahead of time resulting in no conversion processing occurring during playback. Another advantage of computer based DSD to PCM conversion is that if higher performance DSD versions such as DSD 4X appear in the future, they can be easily supported with a software upgrade.

For all of these reasons, DSD capability for the Alpha DAC Reference Series is provided by a state of the art software application, JRiver Media Center, that provides either real time conversion of DSD 1X and DSD 2X to 176.4 kHz, 24 bit PCM during playback or, for the best possible audio fidelity, easy conversion to 176.4 kHz, 24 bit AIFF or WAV files prior to playback. The JRiver Media Center software application is included in the price of the Alpha DAC Reference Series and either Windows OS or Mac OS versions are available.

Specifications

  • Input sampling rate: 32kHz to 192kHz
  • Input word length: 24-bit
  • Ultra low phase noise Precision Clocking at 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz and 192kHz sampling rates ± 100 ppm
  • Two channel analog stereo outputs: XLR balanced with pin 2 positive and RCA unbalanced
  • Digital Inputs: AES – XLR, 110Ω; SPDIF1 – BNC, 75Ω; SPDIF2 – BNC, 75Ω; TOSLINK – Toslink optical connector
  • HDCD decoding detects 16-bit flag at 44.1kHz or 24-bit flag at all sampling rates
  • Multiple digital filter options
  • Balanced analog output level: +18dBu (6.15Vrms) maximum, +12dBu (3.1Vrms) or lower recommended
  • Unbalanced analog output level: 3.25Vrms maximum, 2Vrms or lower recommended
  • Digital volume & balance control: 0.1dB/step with .05dB/step L/R gain trim, 60dB range
  • Frequency response at ≥ 88.2kHz sampling rates: ± 0.1dB from < 0.1Hz to 35 kHz,  – 3dB at 59kHz for 176.4kHz and 192kHz sampling rates
  • Distortion at recommended levels: all products ≤ -120dBFS
  • THD+N at maximum level: < -110dBFS
  • Firmware upgradeable through signal inputs