TEAC 850X (1973) | The Invisible Recorder

 

"Off Duty" was a leisure magazine created for U.S. and Canadian military personnel, offering access to consumer electronics at exclusive military-only prices. Among the standout products frequently advertised were advanced hi-fi and video components, sold at remarkably low U.S. dollar rates through military exchanges. One of the most eye-catching releases featured in the 1973 issue of this magazine was the Teac 850X cassette deck — an innovative model designed to mimic the look and performance of Teac’s open-reel machines. Styled vertically like its reel-to-reel counterpart, the 850X shared the same control layout as the popular Teac 5500 reel to reel recorder.

Highlights of the Teac 850X included:

Three motors and three heads for superior tape handling

Ultra-low wow and flutter (0.065%)

All-solenoid transport, giving it the feel of a professional open-reel deck

Off-the-tape monitoring using a dedicated playback head

Dual-process Dolby noise reduction, with twice the usual number of Dolby circuits for real-time monitoring

Bias settings for CrO₂, standard

Extra features such as pitch control and a memory rewind that stops at counter zero

With its open-reel design philosophy and premium engineering, the Teac 850X also carried an open-reel-style price tag (as per Off Duty magazine 1973) — $579.50 in the U.S. But for military buyers shopping through Off Duty, it represented exceptional value for top-tier audio performance. The black and white picture is how this unit was shown in the "Off Duty" magazine while the colorized version was created by 1001 Hi-Fi.  

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SONY TC-FX7 (1980) | Digic Deck Series

 

The Quartz Lock D.D. (Digic Deck) FX7, with a panel height of 70mm, marks an epoch in the slimming of cassette decks. This high-end "Digic Deck" is a bold new concept that takes on the slimming trend that has become a major trend in recent cassette decks. It achieves a panel height of 70mm, which is considered nearly the limit for an upright see-through type. It's also packed with innovative features, such as a linear electronic counter with digital (minute and second) display, fine feather touch operation, and multi-purpose remote control play. Inside the sharp design exuding the stately style of an advanced deck, it also boasts advanced basic performance, including a quartz-locked D.D. system. Slimming down a cassette deck is also extremely difficult when you add the requirement of erect perspective. This is because the cassette half is about 64mm high, and you also need to ensure space for the head. The FX7 has achieved an ultra-slim panel height of just 70mm within these constraints. Sony has developed the ultra-thin S&F tiny head, and 30 years of know-how in deckbuilding is certainly being put to good use. The electronic counter Digitally counts the tape running time in minutes and seconds. The relationship between the length of the song and the remaining tape, the relationship between the broadcast time and the remaining tape, etc. The TC-FX7 features a Quartz lock D.D. system. Direct drive capstan drive. You can enjoy three different remote controls: the optional RM-80 wireless remote control, the RM-50 wired remote control, and the RM-65 for synchronized play with the player. High-precision recording level adjustment with a width of 100 mm. A multi-function peak program meter with double indication that accurately captures peak values. Logic-controlled fine feather touch operation. 4-stage soft touch tape selector including metal position. 2-motor simple mechanism. Dolby NR. Complete IC. Auto play/memory play. Auto space. REC-MUTE timer standby switch. The TC-FX7 was the matching cassette deck for the Sony Precise slim - mini Hi-Fi system. Main photo shows the TC-FX7 with ST-JX5 tuner, RM-80 remote, MDR-FM7 wireless stereo headphones.

Main specifications: Heads: 1 erase, 1 record/playback; Motors: 1 BSL green motor, 1 high torque motor; Signal-to-noise ratio: 59 dB (Dolby OFF, peak level, DUAD cassette); Frequency response: 20-19,000 Hz (METALLIC cassette); Speed ​​deviation: within ±0.2%; Wow and flutter: 0.05% WRMS; Distortion: 0.9% (DUAD cassette); Dimensions: 430 (W) x 80 (H) x 340 (D) mm; Weight: 6.5 kg; Power consumption: 32 W Original sale price in Germany: 1300 DM

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Marantz CD 3577 (1989) | Class DX One-Bit Conversion for Pure Digital Sound

 

The Marantz CD 3577 marks a true breakthrough in CD player technology. Instead of relying on a traditional Digital-to-Analog Converter (DAC) with its resistor-based limitations, the CD 3577 uses advanced Class DX one-bit conversion to deliver cleaner, more accurate sound. Conventional DACs can introduce zero-cross distortion and low-level non-linearity, especially when processing small audio signals. The CD 3577 eliminates these issues by converting PCM data into Pulse Width Modulation (PWM) using an ultra-high 256× oversampling digital filter. A precision quartz-controlled timing system and a third-order noise shaper push unwanted noise far above the audible range, resulting in exceptional clarity and a superior signal-to-noise ratio. The result is audio that sounds more natural, transparent, and detailed, especially in the subtle low-level information where musical texture and space live. The Marantz CD 3577 reveals the true character of your recordings with accuracy that conventional DAC designs cannot match. The CD 3577 was also a unique model, part of the Century Collection, an ensemble that brings together the most desirable audio and video features into a synergistic group.

SPECIFICATIONS

Digital Filter 256 times oversampling

Frequency Response (+0.-0.5 dB) 4 Hz-20 kHz

Channel Separation 90 dB

Signal To Noise Ratio (A Wtd) 100 dB

Total Harmonic Distortion (20 Hz-20 kHz) 0.01%

Dynamic Range 96 dB

Wow and Flutter Undetectable

Line Out Level/Impedance 2.0 V/1600 ohms

Remote Control Infra-red

Dimensions (W x H x D) 16/16" x 43/32" x 12"

Weight 9.3 lbs.

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