B-I-C T-4M (1979) | 2-Speed 3-Head

The B-I-C T-4M was no ordinary cassette deck. With two tape speeds, full metal-tape capability, and B-I-C's exclusive Broadband Electronics, it pushed the compact cassette format remarkably close to open-reel performance.

B-I-C T-4M Main Specifications

Tape speeds: 4.75 cm/s and 9.50 cm/s

Frequency response at 4.75 cm/s: 20 Hz–21 kHz ±3 dB

Frequency response at 9.50 cm/s: 20 Hz–23 kHz ±3 dB

Wow and flutter at 4.75 cm/s: 0.05% WRMS / 0.09% DIN

Wow and flutter at 9.50 cm/s: 0.03% WRMS / 0.07% DIN

Total harmonic distortion: 1.3% at 4.75 cm/s

Fast-forward/rewind: approximately 48 seconds with a C-60 cassette

Level meters: Peak-indicating LED bar graph, –36 to +9 dB

Drive system: Two-speed tachometer-feedback DC servo motor

Transport: Dual-capstan design

Spooling: DC spooling motor

Dimensions (W/H/D): 440x164x257mm

Weight: 8,4kg

Broadband Electronics was the heart of the T-4M's design. B-I-C developed this circuitry to take advantage of the increased performance available from higher tape speed while maintaining an unusually wide response at the standard 4.75 cm/s cassette speed. At 4.75 cm/s, the T-4M was specified to reach 20 Hz to 21 kHz ±3 dB. Increase the tape speed to 9.50 cm/s and the specification extended to 20 Hz to 23 kHz ±3 dB. That second speed was the real attraction. Running cassette tape at 9.50 cm/s offered substantially more bandwidth and lower wow and flutter, allowing B-I-C to position the T-4M as a cassette deck capable of challenging open-reel machines. Metal tape capability added another advantage. Combined with the higher tape speed and Broadband Electronics, it gave the T-4M the technical foundation for its unusually ambitious performance claims. The transport was equally important. A dual-capstan mechanism and tachometer-feedback DC servo motor were employed to maintain precise tape movement, while a separate DC spooling motor handled fast winding operations. Dolby NR and Signal-to-Noise Performance. Noise reduction was an important part of the T-4M's specification. At 4.75 cm/s, the quoted signal-to-noise ratio was 57 dB, increasing to 65 dB with Dolby NR. At 9.50 cm/s, the figure rose to 61 dB, while B-I-C specified 68 dB with Dolby NR and metal tape. For a cassette deck of its era, these figures demonstrate just how seriously B-I-C approached high-performance recording. The 9.50 cm/s Advantage. Why the higher speed mattered? Tape speed has a direct influence on cassette performance. Increasing the speed from 4.75 cm/s to 9.50 cm/s allowed the T-4M to achieve its widest specified frequency response while also reducing measured wow and flutter. At 9.50 cm/s, wow and flutter was rated at just 0.03% WRMS, compared with 0.05% at the standard speed. The same time you might ask yourself about compatibility with other devices. B-I-C solved this problem by adding a 2-speed car audio cassette deck for all your double speed recordings.

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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.

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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.

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