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