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The standalone digital/analog converter emerged as a product category in 1987 with the appearance of the Arcam Black Box and the Marantz CDA-94, closely followed by the PS Audio Link. The idea was that putting the sensitive D/A-conversion and analog stages in a separate enclosure with its own power supply would maximize the sound quality when compared with packing these circuits in the same box as the transport. However, it turned out that the routing of the digital data between transport and processor in the form of an S/PDIF- or AES/EBU-encoded bitstream could introduce word-clock…
Introduced in early 1998, the Burr-Brown PCM1716 is one of the Tucson company's affordably priced "audio-grade" two-channel D/A converters. Featuring an "enhanced multi-level, sigma-delta architecture" (according to Burr-Brown's website), it is specified as having 24-bit resolution and offering a dynamic range of 106dB. Operating with sampling frequencies of up to 96kHz, it also incorporates an 8x-oversampling digital low-pass filter with digital domain de-emphasis and 82dB stop-band attenuation. Interestingly, this filter can operate with either a sharp or a slow rolloff, depending on the…
Perhaps the acid comparison is with the Arcam Alpha 9 CD player, enthusiastically reviewed by Kal Rubinson in January. With its implementation of the dCS "Ring-DAC," the $1500 Arcam sets the standard for affordable CD replay. I compared the X-24K driven from the Alpha 9's S/PDIF output with the Arcam's analog outputs. (Again, levels were matched to within 0.05dB at 1kHz, and interconnects were identical 6' lengths of Canare cable.) On went the AIDS Benefit centenary tribute to Gershwin, Red Hot + Rhapsody: The Gershwin Groove (Antilles 314 557 788-2)—specifically track 17, David Bowie's "A…
Sidebar 1: Specifications
Description: D/A converter with 24-bit delta-sigma D/A chips, 8x-oversampling digital filter, two S/PDIF digital data inputs (one coaxial, one coaxial in parallel with TosLink optical), and one S/PDIF digital data output. Sampling frequencies supported: 96kHz, 88.2kHz, 48kHz, 44.1kHz, and 32kHz. Frequency response: 20Hz-20kHz, ±0.2dB. De-emphasis error: ±±0.1dB. THD: ±0.006%, 10Hz-20kHz unweighted, ±0.003%, 10Hz-20kHz A-weighted. S/N ratio: >96dB unweighted, >105dB A-weighted. Linearity: ±±0.3dB to -100dBFS.
Dimensions: 4.3" (110mm) diameter by 13" (…
Sidebar 2: Associated Equipment
Digital sources: Mark Levinson No.31.5 and Wadia No.270 CD transports (the No.31.5 connected via a Meridian 518 reclocking unit), California Audio Labs CL-20 and Denon 5000 DVD-V/CD players, Nagra-D open-reel digital recorder, Panasonic SV-3700 DAT recorder. Illuminations Orchid, Madrigal, and Canare 110 ohm AES/EBU cables, AudioQuest and Mod Squad 75 ohm S/PDIF cables. A dCS 972 was also used to upsample CDs to 96kHz and convert the Nagra's 96kHz dual-AES/EBU data output to single, double-speed AES/EBU format.
Comparison digital equipment: Mark…
Sidebar 3: A Caveat
There is one thing to remember when you are thinking of buying any digital processor with a 96kHz-capable unencrypted digital data input: One of the things holding up the setting of the finalized DVD-Audio standard has been the record industry's concern that allowing their 24/96 data to be sent between transports and processors "in the clear" will lead to rampant piracy. (Shyeah—like pirates will not think of putting a DAC/ADC link in the mastering chain.) But it's likely that digital connections will have to be encrypted in some way, which will mean using a FireWire…
Sidebar 4: Measurements
The X-24K had a low output impedance of 49 ohms over most of the audio band, this rising to a still-low 78 ohms at 20Hz. The maximum output level at 1kHz was 2.28V, 1.14dB above the CD Standard's 2V. The channel separation (fig.1) was simply superb. Surprisingly, the Musical Fidelity processor inverted absolute polarity.
Fig.1 Musical Fidelity X-24K, channel separation at 0dBFS (R-L crosstalk dashed, 10dB/vertical div.).
Its CD-bandwidth frequency responses with and without de-emphasis (top and bottom pairs of traces, respectively) are…
Note the convergence of the traces below 200Hz, which can also been seen in the spectra of the Musical Fidelity's output while it decodes "digital black" data (fig.8). I suspect that this is due to the unit's low-frequency noise performance being limited by the highish impedance of the wall-wart power supply. A bigger, stiffer transformer might work some magic in the bass.
Fig.8 Musical Fidelity X-24K, spectrum of digital silence with 16-bit data (top) and 24-bit data (bottom). (1/3-octave analysis, right channel dashed.)
As suspected from these noise-floor graphs, the X…
I was in a jam. John Atkinson was gently reminding me of rapidly approaching deadlines, and my longtime reference CD player, the Simaudio Moon Eclipse, had just been recalled for an upgrade. This wouldn't normally have been a problem, but I was also in the middle of relocating from New Mexico to California, and all of my backup gear was either in storage or on a moving truck somewhere.
I needed a digital front-end, but which one? I abhor complexity, so I wanted an integrated unit. I'm picky, so it had to be something that sounded good. I wanted to be realistic, so it couldn't…
I poured a glass of a wine and cued up Mozart's Flute Quartet in D, K.285, which opens the Santa Fe Chamber Music Festival's Serenade CD (Stereophile STPH009-2, engineered by JA), and sat back to listen. My first impression was one of an easy vibrance—a rich, flowing sound that seemed to coax the tension out of me. As I melted into the music, I could feel my shoulders lowering, my hands loosening their grips on my chair's arms. The soundstage seemed to envelop me and fill the room, Mozart's lines flowing through it with a liquid-like coherence.
But within this smooth, vibrant…