Analog Sources: Dr. Feickert Analogue Blackbird turntable, Jelco TK-850L tonearm, My Sonic Lab Ultra Eminent Ex cartridge.
Digital Sources: Apple Mac mini computer running Audirvana Plus 3.2; Schiit Audio Yggdrasil, HoloAudio Spring "Kitsuné Tuned Edition" Level 3, Mytek Brooklyn+ & Manhattan II DACs, Chord Qutest, PS Audio DirectStream & Digital Link DACs.
Preamplification: Rogue Audio RP-7 line-level preamplifier.
Power Amplifiers: First Watt SIT-3, Pass Laboratories XA25, Rogue Audio Stereo 100.
Loudspeakers: Harbeth Monitor 30.2…
search
Sidebar 2: Associated Equipment
Sidebar 3: Measurements
I measured the Balanced Audio Technology VK-56SE using my Audio Precision SYS2722 system (see the January 2008 "As We See It"). The VK56-SE looks identical to the VK-55SE, which Wes Phillips reviewed in April 2010, and it was instructive to compare its measured performance with that of the earlier amplifier. Like the VK-55SE, the VK-56SE has four output terminals for each channel, various pairs of which can be used to provide a feed from three different output-transformer taps labeled High, Med, and Low. I performed a complete set of measurements from each tap,…
Manufacturer's Comment
Editor: I would like to thank Herb Reichert for his time, effort, and wonderful enthusiasm with regards to the BAT VK-56SE power amplifier, as well as to John Atkinson for his detailed and insightful measurements. The fact that this amplifier drove Herb' s loudspeakers in a way he preferred over both of his highly regarded in-house reference amplifiers speaks volumes about the VK-56SE's unique and uncanny sonic merits. This is an amplifier that truly brings you much closer to the music.
The BAT VK-56SE is the result of the evolution of medium-powered tube…
If there's one buzzword in high-end audio for the 1990s, it's undoubtedly jitter (footnote 1). "Jitter" describes timing variations in the clock controlling the ones and zeros that represent the analog audio signal. If that clock isn't stable to an extraordinarily precise degree, the sound quality of the digital processor will be degraded.
A CD transport/digital processor combination introduces jitter in three ways: 1) the transport puts out a jittered signal; 2) the S/PDIF or AES/EBU interface between the transport and processor creates jitter; and 3) the digital processor adds its own…
All input receivers have some frequency at which they begin to reject jitter rather than pass it to the output clock. Above this frequency, called the "Jitter-Attenuation Cutoff Frequency" (JACF), jitter is rejected. Below the JACF, jitter is passed to the recovered clock. The DTI Pro's claimed JACF is a very low 5Hz, presumably making the output clock completely immune to signal-correlated jitter.
Other circuit details: The dual-PLL scheme works only with 44.1 and 48kHz sampling frequencies. For 32kHz decoding, the CS8412 operates without benefit of the second PLL. The output driver is…
I'm always suspicious when I hear more detail; it's easy to mistake an etched and analytical character for increased resolution. I have no such reservations about the DTI Pro; not only was it more resolving of detail, but the presentation was actually smoother and more liquid. In particular, the treble was softer and gentler, with a greater liquidity and freedom from hash. Similarly, the mids were less hard and strident, giving the presentation a greater sense of ease. I also heard more air and bloom around the treble; cymbals seemed to hang in space, surrounded by air.
That's not all.…
Sidebar 1: System
I auditioned the three jitter attenuators with high- and low-quality transports, with a processor susceptible to interface jitter (an older PS Audio UltraLink that uses the Yamaha input receiver), and with processors that easily reject jitter, such as the Mark Levinson No.30.5, which has near-total immunity to interface jitter. Since the No.30.5 is the first processor on the market to use the NPC5842 filter, which can pass 20-bit data (actually up to 24-bit data), it was ideal for fully assessing the DTI Pro's 20-bit output word mode and claimed resolution enhancement…
Sidebar 2: Measurements
The ideal test instrument for measuring jitter in the S/PDIF outputs of jitter-reduction devices is the UltraAnalog unit, which takes in an S/PDIF (or AES/EBU) signal and outputs its jitter component. The jitter can then be measured as an RMS voltage, plotted spectrally, or even listened to. Unfortunately, there's only one such analyzer in existence, and although we had been able to borrow the unit in the past, this time UltraAnalog couldn't part with it—even briefly.
Consequently, I measured the effects of these jitter-reduction devices inside a digital…
Sidebar 3: Specifications
Audio Alchemy DTI Pro: Jitter attenuator with DSP "resolution enhancement." Inputs: TosLink, coaxial (BNC jack), AES/EBU. Outputs: coaxial (BNC), ST-type optical, and AES/EBU. Output word length: 16 bits, 18 bits, 20 bits (user selectable).
Dimensions: 8.5" W by 2" H by 6.5" D. Weight: 4 lb.
Price: $1295(1994); product no longer available (2019). Approximate number of dealers: 120.
Manufacturer: Audio Alchemy, Inc., Westlake Village, CA 91362 (1994); Audio Alchemy LLC, 7960 Pearl Street, Ventura, CA 91320. Tel: (805) 794-2418. (2019). Web: www.…
British digital-audio specialists dCS (Data Conversion Systems) has been on a roll. Since the September 2015 introduction of the Rossini DAC ($23,999), the single-box Rossini Player ($28,499), and the Rossini Clock ($7499), they've released a number of new products and software/firmware updates. In 2016 came network firmware updates that established dCS DACs and Players as Roon endpoints. 2017 brought improved (v1.05) software for the Rossini DAC and Player, and 2018 an update to process MQA, followed by the October 2018 introduction of the Rossini upsampling SACD Transport ($23,500—see John…