STAX CDP QUATTRO (1986) | High Resolution QUATTRO

The STAX CDP QUATTRO was Stax’s first CD player, introduced in 1986 at a time when digital audio was still a relatively new technology. Combining a Yamaha-made CD mechanism with Stax-developed digital and analog circuitry, it took an unusually uncompromising approach to mechanical isolation, noise reduction, and signal processing.

STAX CDP QUATTRO – Specifications

Model: STAX CDP

Release: 1986

Digital processing: 16-bit, 4x oversampling digital filter

Oversampling frequency: 176.4 kHz

D/A conversion: Separate DACs for left and right channels

Frequency response, Direct Out: 0.7 Hz–20 kHz, ±0.5 dB

Frequency response, Filtered Out: 0.4 Hz–18 kHz, ±0.5 dB

Signal-to-noise ratio: 104 dB or higher

Dynamic range: 96 dB or higher

Total harmonic distortion: 0.002% or less at 0 dB, 1 kHz

Crosstalk: -100 dB or less, 5 Hz–16 kHz

Dimensions: 435 × 165 × 290 mm

Weight: 8.0 kg

Original sale price in Japan: ¥270,000

Stax’s Proprietary Circuit and Chassis Design. The two-tier chassis is one of the most distinctive aspects of the STAX CDP QUATTRO. Rather than simply placing one component on top of another, Stax built the player around a sturdy wooden board supported by tall aluminum pillars. The CD mechanism sits above the board, while the electronic section is suspended underneath. Mechanical and electrical separation was taken particularly seriously. The mechanism section and electronics section were separated, including their power arrangements, to reduce unwanted mechanical and electrical interaction. The electronic circuitry was housed in a wooden chassis designed to provide protection from electromagnetic interference. A Digital Filter Designed to Minimize Analog Filtering. The 4x oversampling system was central to Stax’s approach to digital audio. A CD uses a 44.1 kHz sampling frequency. During digital-to-analog conversion, unwanted higher-frequency components can appear alongside the audio signal and normally have to be removed with an analog filter. Stax instead used a 16-bit, 4x oversampling digital filter, raising the sampling frequency to 176.4 kHz. This pushed unwanted components much farther away from the audible band. The result was that a relatively low-order analog filter could be used rather than a more complex high-order design. Discrete FET Analog Amplifier. The analog amplifier section used an all-FET discrete amplifier designed for high-speed response and good linearity. Stax also paid considerable attention to the deglitch circuit following the D/A converter. Instead of relying on operational amplifiers, the circuit used discrete components and a balanced-charge MOS FET arrangement intended to minimize switching-related spike noise. Separate Left and Right DACs. The dual-DAC configuration used independent ladder-type converters for the left and right channels. This arrangement was designed to maintain accurate channel separation and eliminate phase differences between the two channels. The specification lists an impressive 0° L/R phase difference from 5 Hz to 20 kHz, together with crosstalk of -100 dB or less. Direct and Filtered Outputs. Two output approaches were provided. The Direct Out was intended to take advantage of the player’s digital processing and allow the signal to be output without a conventional analog filter. For applications such as tape recording, where unwanted high-frequency components could potentially produce beat frequencies, Stax also provided a Filtered Out using a gently tuned third-order Bessel analog filter. Absolute Phase Switching. A rear-panel phase switch allowed the absolute phase to be inverted by changing the digital data. This was an unusual feature and reflected Stax’s attention to subtle aspects of signal reproduction.

Looking for more? Head to 1001hifi.com for more.

Like Our Work? Support 1001 Hi-Fi

Gallery

Sansui AU-X1111 MOS VINTAGE (1988) | The Double Eleven Integrated Amplifier

The Sansui AU-X1111 MOS VINTAGE is the final 1988 model in Sansui's legendary series of “The 1” amplifiers, following the AU-X1 (1979), AU-X11 (1982), and AU-X111 MOS VINTAGE (1985). Known as “Double Eleven,” this flagship integrated amplifier combines Sansui's balanced circuit philosophy, MOS FET power devices, and exceptionally robust construction in a 35.1 kg design aimed squarely at serious music reproduction.

Sansui AU-X1111 MOS VINTAGE Specifications

Year: 1988

Power output: 110 W + 110 W into 8 ohms, both channels driven, 20 Hz–20 kHz

Power output: 150 W + 150 W into 6 ohms

Total harmonic distortion: No more than 0.008% at rated output

Intermodulation distortion: Less than 0.008%

Slew rate: 150 V/µs at 8 ohms

Rise time: 0.5 µs

Damping factor: 200 at 8 ohms

Frequency response: DC–300,000 Hz from CD input

Signal-to-noise ratio: 88 dB, PHONO MM

Signal-to-noise ratio: 110 dB, CD/TUNER/LINE and TAPE/DAT

Subsonic filter: 3 dB at 16 Hz, 6 dB/octave

Muting: 20 dB

Presence control: +2 dB at 200 Hz; +6 dB at 10 kHz with volume at -30 dB

Power supply: 230 V, 50/60 Hz

Nominal consumption: 350 W / 560 VA

Maximum power consumption: 820 W

Dimensions: 470 × 178 × 486 mm

Net weight: 35.1 kg

Original sale price in Germany: 6.500 DM

MOS FET power devices are at the heart of the AU-X1111 MOS VINTAGE. Sansui selected these devices as part of its continuing pursuit of high-fidelity amplification and used them within an amplifier architecture developed through years of circuit refinement. The AU-X1111 represents the culmination of a design philosophy that Sansui had been developing since its wide-range DC amplifier of 1976. Balanced transmission and amplification became a defining element of Sansui's approach, particularly following the introduction of the B-2301 in 1983. The company combined this philosophy with a twin-mono construction intended to optimize the amplifier's essential structural requirements. Over the years, Sansui developed a series of distinctive technologies, including the diamond differential circuit, non-magnetic flux-free design, Super Feedforward, ground floating circuit, and twin-diamond balanced drive circuit. The AU-X1111 MOS VINTAGE brings this accumulated experience together in a single integrated amplifier. Its unusually wide DC–300 kHz frequency response, 150 V/µs slew rate, and 0.008% maximum THD reflect the engineering priorities of Sansui's flagship designs of the period. Why the AU-X1111 Is Special? The “1111” designation was deliberate. Sansui presented “1111 = Double Eleven” as its answer to the pursuit of sound quality and positioned the AU-X1111 as a new expression of its amplifier philosophy. Rather than treating the amplifier simply as a collection of technical specifications, Sansui emphasized the relationship between technology and musical expression. The company described the AU-X1111 as the result of continuous refinement in circuits, mechanisms, and components, with quality parts developed through the history of its amplifier designs.

Looking for more? Head to 1001hifi.com for more.

Like Our Work? Support 1001 Hi-Fi

Gallery

AIWA DR-1, DR-2 (1985) | Computer Love

The DR-1 and DR-2 from Aiwa employs a proprietary digital signal waveform processing circuit. These data recorders were designed to meet the demands of the new digital age. The digital signal waveform processing circuit drastically reduces errors. Aiwa's advanced technology has finally addressed the loading errors that have plagued us until now. The adoption of a unique digital signal waveform processing circuit has dramatically reduced errors. Furthermore, features such as completely automatic level adjustment have dramatically improved reliability and ease of use. It's also perfectly compatible with PCs. Digital signal waveform processing. Digital signal waveform processing circuit: Even distorted analog signals are corrected into digital signal waveforms that are easy for computers to interpret. This reduces errors due to dropouts and phase shifts, achieving a level of reliability not possible with conventional data recorders.

Specifications DR-1

Achieves high-speed processing via RS-232C, far exceeding traditional floppy disk transfer rates. | Includes a multi-functional, advanced TOS (for PC-8801 series), enabling recording equivalent to approximately 10 floppy disks. | <Graphics> Fast screen saving/loading (55 seconds), and high-speed file searching are also possible. Auto-rec mute mechanism | Phase switching switch | Access indicator Tape speed: 4.75cm/sec | Supported transfer speeds: CMT mode 600-2,400bps, RS-232C mode 600-9,600bps | Compatible tapes: CMT mode normal tape (TYPE1), RS-232C mode metal tape | Maximum external dimensions: Width 175 x Height 112 x Depth 260mm | Weight: 2.5kg | Power supply: AC100V (50/60Hz) | Accessories: RS-2320 dedicated cable, TOS tape for PC-8801 series | original sale price in Japan ¥28,500

Specifications DR-2

Achieves double-speed loading. (MSX1200 baud tape) | Includes a sub-out terminal that processes backup tapes with digital signal waveforms. | Convenient MOTOR button for saving/loading | Phase switching switch | Tape speed: 4.75/9.5 cm/sec | Supported transfer speed: 600-2,400 bps | Tape type: Normal tape (TYPE 1) | Maximum external dimensions: Width 166 x Height 128 x Depth 146 mm | Weight: 1.2 kg | Power supply: AC100V (50/60Hz) | Original sale price in Japan ¥12,800

Looking for more? Head to 1001hifi.com for more.

Like Our Work? Support 1001 Hi-Fi