PIONEER CT-939 (1988) | The Reference Master Cassette Deck

What if you inserted a conventional compact cassette, pressed Play, and suddenly wondered if you were listening to digital audio? The answer is the Pioneer CT-939, a three-head flagship cassette deck engineered around extremely stable tape transport, short signal paths, low vibration, and precision recording and playback circuitry.

Pioneer CT-939 Main Specifications

Type: 4-Super/2-Channel Recording and Playback Stereo Cassette Deck

Head configuration: Three-head design

“Laser Amorphous” playback head × 1

Hard Permalloy recording head × 1 (combined)

Dual-Gap Ferrite erase head × 1

Motors:

DC servo motor for capstan drive × 1

DC motor for reel drive × 1

DC auxiliary motor × 1

Wow and flutter: 0.024% WRMS; ±0.06% DIN

Rewind time: 80 seconds with C-60 tape

Frequency response:

Normal tape: 20–21,000 Hz (-20 dB)

Chrome tape: 20–21,000 Hz (-20 dB)

Metal tape: 20–22,000 Hz (-20 dB)

Signal-to-noise ratio: 60 dB, Dolby off

Distortion: 0.6% at 0 dB

Inputs: MIC, 67 mV / 50 kΩ; LINE

Power supply: 220 V or 240 V, 50–60 Hz

Dimensions: 420 × 133.5 × 372 mm

Weight: 9.6 kg

The Pioneer CT-939 “Reference Master” Technology. The tape transport is at the heart of the CT-939. Pioneer designed the mechanism around a dual-capstan drive intended to optimize tape contact with the playback head. Two differently sized capstans, together with the guide rollers, help reduce resonances generated by moving parts. The enclosed tape path further contributes to the highly stable transport associated with the “Reference Master” drive. Precision playback starts at the head. The CT-939 uses a precision-machined amorphous playback head, while the three-head configuration separates the recording, playback, and erase functions. A cassette stabilizer holds the cassette securely in position while helping damp vibrations that could affect sound purity. Short Signal Paths. Pioneer also concentrated heavily on the signal circuitry. Signal paths between the input and recording head, and between the playback head and output, were kept extremely short. The recording and playback circuits for the two channels are completely separated to minimize interference and distortion. The playback amplifier uses non-inductive circuitry with direct head connection, designed to reduce magnetic distortion while improving linearity. Vibration Control and Chassis Construction. Mechanical stability extends beyond the tape transport. The CT-939 uses a robust copper-plated chassis, honeycomb-reinforced construction, cassette damping, honeycomb-structured dampers, and a cast-encased transformer. The specially damped transformer is made from solid cast iron and incorporates three separate OFC windings intended to prevent interference. The power supply is a low-impedance, servo-controlled, high-speed design, with separate supplies for the amplifier, control, and display stages. Recording and Noise-Reduction Features. The CT-939 combines its transport and circuit design with extensive recording controls. Dolby HX Pro extends dynamic range in the high frequencies, while Dolby B and C noise reduction provide additional noise reduction. The deck also includes fine adjustment of recording bias current, allowing the bias to be adjusted for the tape being used. An automatic tape-type selection system simplifies operation with different cassette formulations. Pioneer CT-939 User Features. Despite its ambitious engineering, the CT-939 was designed for straightforward operation: Automatic monitor switches from Source to Tape when recording begins, Switchable fluorescent level meter with peak hold, Narrower meter range for increased resolution, One-button recording start, Mute recording with automatic blank-space correction, Electronic tape counter with three display modes, Motorized cassette ejection, Headphone output with level control, Timer capability for recording and playback, MPX filter, Skip function for direct access to the beginning of the 15th track in either tape direction. The CT-939 was a AC220V, 240V model while the CT-800 was the AC120V model. Original sale price in Germany: 1200 DM.

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Lo-D DA-703D (1987) | 4DAC - Vibration Cut Solid Base

Released by Lo-D (Hitachi) in 1987, the Lo-D DA-703D was a solidly built integrated CD player developed during the company’s growing focus on digital audio. Its standout feature was an unusually comprehensive approach to vibration control, combined with sophisticated digital processing and a carefully separated digital/analog circuit design.

Lo-D DA-703D Main Specifications

Release year: 1987

Frequency response: 5–20,000 Hz ±0.5 dB

Dynamic range: 100 dB (EIAJ)

S/N ratio: 110 dB (EIAJ)

Channel separation: 105 dB (EIAJ)

Harmonic distortion: 0.003% (EIAJ)

Wow and flutter: Measurement limit, ±0.001% W. peak

Output voltage: 2.0 V

Power consumption: 16 W

Dimensions: 435 W × 129 H × 337 D mm

Weight: 10.5 kg

Digital filter: 4× oversampling

D/A conversion: High-dynamic 4DA converter

Optical output: Provided

Track programming: Up to 24 tracks

Remote control: 20-key keypad

Player controls: 10-key keypad

VC (Vibration Cut) Technology

The DA-703D’s defining feature was its extensive "VC (VIBRATION CUT) mechanism," designed to control unwanted vibration throughout the player. The chassis was firmly supported by a high-rigidity VC solid base made from a special high-density resin. This was further supported by a large three-piece insulator with a 64 mm diameter. Between the main body and VC solid base, 60 cylindrical absorbers were randomly positioned on the contact surface. Their positions were determined using computer simulation analysis, with the aim of effectively preventing vibration from affecting the player. The heavy VC solid base also lowered the overall center of gravity. It helped shift the center of gravity away from the pickup area and toward the center of the chassis. The enclosure itself used a VC enclosure sandwich structure, while the disc table and front panel were separated and floated through a VC loading mechanism. The pickup assembly was mounted on a VC pickup unit made from VC metal. This construction used two steel plates with a thin viscoelastic polymer material sandwiched between them. Three-Spot Pickup System. The pickup system used three laser spots rather than relying solely on the main laser beam. The main beam read the CD signal, while two additional beams positioned to the left and right helped detect tracking errors. The tracking actuator used a pure-metal damping suspension system, designed to provide effective vibration damping during operation. The player also incorporated a direct pit servo system. This system detected tracking errors through reflected laser light while also checking for subtle disc warping and micron-sized dirt. The aim was to prevent unnecessary actuator movement and maintain accurate tracking. 4× Oversampling Digital Filter. Digital processing was another major feature of the DA-703D. Its 4× oversampling digital filter converted the original sampling frequency to 176.4 kHz, allowing high-speed processing and more effective removal of high-frequency noise. The system also suppressed glitch noise produced during digital signal switching. According to the original design description, this eliminated the need for sample-and-hold circuits and low-pass filters, contributing to improved phase and frequency-response characteristics. High-Dynamic 4DA Converter. The D/A converter used four converters rather than two. Where early CD players commonly used one D/A converter for each stereo channel, the DA-703D used two converters per channel, for a total of four. Left and right channels could therefore undergo D/A conversion independently and simultaneously, minimizing timing and phase differences between the channels. The design achieved a stated 24-bit conversion accuracy range. Digital and Analog Circuit Separation. Lo-D also paid considerable attention to electrical isolation. The power supply completely separated the digital and analog sections, with each section receiving its own independent power transformer. This produced a two-transformer configuration intended to reduce interference between the two sections. Five photoisolators were used for optical transmission between digital and analog circuits, providing further electrical isolation. An optical output was also provided for connection to an external D/A converter. The analog section was separated internally as well. The D/A converter and following analog circuitry were separated to suppress interference, while the left and right analog channels were arranged symmetrically. Dedicated components, including high-quality capacitors, high-speed diodes and extra-thick power cords, were also selected for the design. Programming and Playback Features. The DA-703D was more than a basic CD transport and converter. The player featured a 10-key keypad, while its remote control provided 20 keys. Direct track selection was available, together with random programming of up to 24 tracks. A delete-program function allowed unwanted tracks to be excluded from playback. The DA-703D offered six repeat functions covering: All tracks, Random memory, Section, Single track, Random play, Delete, Total Edit Function. The total edit function was designed with cassette recording in mind. It allowed tracks to be arranged for both sides of a cassette tape according to the desired recording length. The unusual Twin Line Music Table display made this easier to manage. The display showed 20 tracks in two columns, with programmed and scheduled tracks on the upper line and completed tracks on the lower line. This made functions such as total editing and random playback easier to follow. The Lo-D DA-703D was a serious CD player with an unusually logical engineering approach. Its combination of extensive vibration control, three-spot tracking, 4× oversampling, four-D/A conversion and digital/analog isolation shows how much attention Lo-D devoted to extracting reliable performance from the emerging CD format. Original sale price in Japan ¥89,800

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GRUNDIG RR 1040 (1979)

 

Introduced in 1979 the RR 1040 by Grundig in addition to a large, easily readable scale and an excellent signal strength meter adds a digital frequency display. Thus the Grundig RR 1040 makes radio station searching a real pleasure. Especially on shortwave, the directly readable reception frequency helps to find the desired station. In terms of ease of use, this Grundig model was superior to its Far Eastern competitor, as the FM station buttons allow for lightning-fast selection between... read more.