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The Lazarus, a slim, quite elegant unit finished in black with red and gray legends, lived up to its advance billing: it literally rose from the dead! Out of its coffin (ie, shipping box) and plugged into the wall, it showed no signs of life. Troubleshooting revealed a blown AC mains fuse. That in itself was not a major problem, but what worried me was the root cause of the trouble. Preamplifiers as a rule are not power-hungry, so a current surge at turn-on sufficient to destroy the 250mA slow-blow mains fuse appeared symptomatic of a major circuitry failure.
Sidebar 1: Absolute Issues
Why should the Cascade Basic be so sensitive to polarity reversal? I can only speculate and point an accusing finger at the possibility that inherent phase-response errors are compounding the effects of polarity reversal. A nonlinear phase response will produce a frequency-dependent phase shift of harmonics in a complex tone, the end result being a distortion of the signal waveform. So the broad issue is whether the auditory system is sensitive to waveform distortion or to changes in waveform slope (a polarity reversal changes the slope of the signal; ie, a…
In hindsight, it was inevitable that two sophisticated digital audio technologies—software-based digital filters and Bitstream D/A converters—were destined to be married in one product. The software-based D/A converters offered by Krell, Wadia, and Theta all used multi-bit ladder DACs, and Bitstream-based units have previously relied on off-the-shelf digital filters.
Having auditioned both types of technologies individually, I've always wondered how they would sound together. This is an important question; fewer and fewer IC manufacturers will make multi-bit DACs as the world—for better…
Sidebar 2: Measurements
Intrigued by Dick's description of the Lazarus preamp's phono stage as having "zippy" treble transients, I ran a low-level 1kHz squarewave through the magazine's inverse RIAA network into the Cascade Deluxe's phono input (set to 47k ohms impedance). Fig.1 shows the result at the tape output sockets: excessive leading-edge overshoot which will certainly lend an "etched" quality to the sound in the treble, as well as exaggerate the audibility of disc surface noise. Note also the slight uptilt to the plateau of the waveform, implying too much upper-bass energy. The…
Parts quality is very high. The capacitors associated with the Bitstream DAC are primarily polystyrene, all resistors are 1% metal-film types, and four of the resistors in the feedback loop are $3 non-inductive wirewound types. These resistors reportedly had a huge effect on the Prime's sound quality. In addition, a few Teflon capacitors (very expensive) are used in critical audio stages. The metal work is zinc over copper over steel, and the pcb is glass epoxy.
Overall, the Prime is an engineering marvel for its modest price. There is far more inside the unit than one would expect for…
Sidebar 3: Specifications
Description: Tube preamplifier with hybrid solid-state/tube phono design. Frequency response: 20Hz–20kHz, +0/–1dB. High-level sensitivity: 100mV in for 1V out. Phono sensitivity: 0.2mV for 0.5V output at 1kHz. Phono overload: 50mV (no frequency specified). Phono input impedance: adjustable from 26 ohms to 47k ohms in 8 steps, in parallel with 25pF. Line input impedance: 100k ohms. Measured output impedance: 1030 ohms.
Dimensions: 19" W by 10" D by 2" H.
Serial number of sample tested: 2062.
Price: $1199 (1989); no longer available (2015). Approximate…
Sidebar 1: Review System
The Prime took center stage in my digital front end for the past two and a half months. It was driven primarily by Theta's Data CD transport through Theta's own digital interconnect. The preamplifier was either the extraordinary Audio Research LS2 reviewed last month or the EVS Stepped Attenuator, a passive level control.
Loudspeakers were the Hales System Two Signatures augmented by the Muse Model 18 subwoofer, driven by VTL 225W Deluxe Monoblocks. Interconnects were the AudioQuest Diamond and Lapis or Straight Wire Maestro, and speaker cable was bi-…
Sidebar 2: Measurements
This is the first set of measurements using Stereophile's Audio Precision System One with the new "Dual Domain" upgrade. Unlike a standard System One, the Dual Domain can generate and analyze signals in the digital domain. Previously, digital signals for testing D/A converters were read from suitable test discs and taken from the digital output of a CD player. With the Dual Domain, we can generate a variety of chosen signals rather than being stuck with only the signals of test CDs. In addition, the Dual Domain has waveform capture (with 16-bit resolution) and FFT…
Sidebar 3: Specifications
Description: 4x-oversampling software-based D/A processor with Bitstream DAC. Digital filter: 4x-oversampling Theta composite filter using one Motorola 56001 DSP chip. D/A conversion: 64x-oversampling Philips Bitstream DAC. Frequency response: DC–20kHz +0dB, –0.4dB. THD+N –104dB at 1kHz referenced to full scale. Output impedance: 50 ohms.
Dimensions: 19" W by 2.5" H by 10.5" D. Weight: 14 lbs net, 16 lbs shipping.
Price: $1250 (1991); no longer available (2015). Approximate number of dealers: 90.
Manufacturer: Theta Digital, Agoura Hills, CA 91301 (…
Manufacturers' Comment
Editor: It is, of course, disappointing to receive an unfavorable review. A product designed and voiced at this level is inherently an opinion carefully stated. Michael's review is as well, and we differ. As Michael says, "that's hi-fi." We strive for fast transient ability and very low distortion. These are the qualities that we feel bring the ability to "hear the room," the 3D character of the recording space, the soundstage that removes the speakers' locations from the listener's perception. For us, this is the challenge. It is how we design and voice our systems…