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In the November 1994 issue of Stereophile, Robert Harley reviewed three products that were intended to reduce word-clock jitter in an S/PDIF or AES/EBU serial datastream: the Audio Alchemy DTI Pro, the Digital Domain VSP, and the Sonic Frontiers UltrajitterBug. (All three handle 16-bit data sampled at rates of 44.1kHz and 48kHz.) This review was published before Paul Miller and the late Julian Dunn created the J-Test signal, which combines a high-level tone at exactly one quarter the sample rate (Fs/4) with a low-level squarewave at 1/192 the sample rate produced by toggling the LSB. (This…
Of the celebrated triumvirate of John Scofield, Pat Metheny, and Bill Frisell—the most original and influential jazz guitarists of the past 50 years—none is more distinctive, or self-effacing, than Frisell, a true changeling of the guitar. Frisell is a jazz-based musician, but his music crisscrosses genres, and his guitar playing isn't bound to or limited by a specific technique. He's a master illusionist, able to alter a song's meaning far beyond its original intent with the aid of a Telecaster guitar, a modest effects chain, and, most importantly, his rich imagination. In concert—as I…
Tell me now: When you're there in the scene, watching Lord Voldemort chase Han Solo through the Cave of the Klan Bear, how often do you notice that the sounds you're experiencing are being pumped at you from five black-painted room boundaries, while the flickering-light images approach from only one? Moreover, in a parallel, more quotidian reality, you're sitting upright in your seat, noisily chomping popcorn while absorbing—and processing—massive amounts of sensory data: Did you ever consider the sensual, mechanical, and psychological complexity of a moment like this, and how fundamentally…
"Since the amplifier damping factor plays no role and the cables need to be terminated with more than 2 ohms, then we can use a resistor of any convenient value connected in series to the headphones and their cable. As far as the ribbon is concerned, this is a current-source operation mode.
"The RAAL specs say: Impedance: 0.018 ohms; Sensitivity: 85dB/1mW; Power Handling With Bass-Heavy Tracks: 450mW RMS; Max SPL at 450mW RMS (limited by ribbon excursion at LF): 111dB.
"To develop 450mW of power at 0.018 ohms load, we need 5 amps RMS."
Listening with the Schiit Aegir
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From the front, the LS5 looks identical to Audio Research's popular LS2: two knobs on either side of the Audio Research nameplate, and a row of toggle switches along the bottom. But that's where the similarities end; the LS5 is a completely different animal from the LS2, or even the balanced LS2B.
For starters, the LS5 is fully balanced from input to output. To understand the difference between a preamp with balanced inputs and outputs and a truly balanced preamp like the LS5, let's look at how most balanced input and output preamps process a balanced input, using the LS2B as an example…
Robert Harley returned to the LS5 in November 1994 (Vol.17 No.11):
While I was auditioning the $4495 Audio Research LS5 Mk.I preamplifier that I reviewed in August, I took possession of the $3495 Sonic Frontiers SFL-2. As much as I liked the Audio Research, it was clear that the Sonic Frontiers was serious competition. In some respects, the SFL-2 was the winner. The Sonic Frontiers had a cleaner treble, with less grain. In fact, it was the SFL-2's lack of treble grain that pointed out the LS5's trace of edge on instrumental textures. The SFL-2 revealed that the LS5 had a very slight…
While I was auditioning the $4495 Audio Research LS5 Mk.I preamplifier that I reviewed in August, I took possession of the $3495 Sonic Frontiers SFL-2. As much as I liked the Audio Research, it was clear that the Sonic Frontiers was serious competition. In some respects, the SFL-2 was the winner. The Sonic Frontiers had a cleaner treble, with less grain. In fact, it was the SFL-2's lack of treble grain that pointed out the LS5's trace of edge on instrumental textures. The SFL-2 revealed that the LS5 had a very slight…
Sidebar 1: Robert Harley's System
The LS5 Mk.II has been part of my reference system for the past few months. I also had on hand an original LS5 for side-by-side comparisons at matched levels, to refresh my memory, as well as a Sonic Frontiers SFL-2. The associated components I used to evaluate the LS5 Mk.II included Audio Research's VT150 tubed monoblocks—the best power amplifiers I've heard in my system. While I had some criticisms of the original LS5, I had absolutely no reservations about the VT150's wonderful musicality. Loudpeakers were Thiel CS3.6es—a moderately difficult load,…
Sidebar 2: Measurements
BL2 Input Controller: The BL2 had a very high input impedance of 1.14M ohms, a little lower than the specified 1.5M. At these high impedances, however, an accurate measurement is difficult to obtain. Output impedance was a very low 55 ohms across the band.
The BL2's gain into a 100k load was 5.93dB, fractionally under the 6dB to be expected from converting a single-ended signal into a balanced signal. DC offset levels were quite low, measuring 4.3mV (left channel) and 1.5mV (right channel). The input overload point was greater than 13V RMS.
The…
Sidebar 3: Specifications
LS5 preamplifier: Fully balanced, pure vacuum-tubed line-stage preamplifier. Tube complement: six 6922 dual triodes, six 12BH7 dual triodes. Frequency response: 1Hz–100kHz ±0.5dB (–3dB points below 0.1Hz and above 250kHz). Distortion: <0.01% at 2V RMS output (typically <0.005% in midband). Gain: 30dB/12dB switchable. Input impedance: 200k ohms balanced. Output impedance: 400 ohms balanced. Maximum input level: 20V. Controls: Gain, Input Selector, Power On/Off, 30dB/12dB Gain, Monitor/Source, Mute/Operate. Noise: 40;uV RMS residual IHF weighted balanced…
At the 1992 Winter Consumer Electronics Show in Las Vegas, Audio Research showed a line of reference products that represented the pinnacle of founder William Z. Johnson's life work as an amplifier designer (footnote 1). Although the all-tubed, fully balanced preamplifier and tubed monoblock power amplifiers were shown as works-in-progress, it was clear that these were products aimed at advancing the state of the amplifier art with no consideration for cost. Indeed, the reference preamplifier and monoblock power amplifiers were a return to Audio Research's roots, and a personal statement by…