The Technics RS-1700 represents one of the most technically ambitious consumer-oriented open-reel tape decks ever produced, arriving as a direct evolution of the already-celebrated RS-1500US and bringing with it a set of engineering refinements that placed it in rare company at the top of the high-fidelity reel-to-reel market. Where the RS-1500US had introduced the world to Technics‘ “Isolated Loop” tape path, the RS-1700 took that foundational concept and built something genuinely novel around it: a fully symmetrical, bidirectional transport capable of recording and playing back in either direction with statistically identical performance.
The centrepiece of the RS-1700’s design is that Isolated Loop transport, formed around a single 34mm capstan of exceptionally large diameter, a reversing roller, and a matched pair of pinch rollers applying equal pressure on each side. The geometry of this arrangement is not merely cosmetic. Because the tape is wrapped and tensioned identically in both directions of travel, the machine produces the same low wow and flutter figures regardless of which way the tape is running.
Technics were justifiably proud of the 0.018% WRMS wow and flutter figure at 15 ips, and they were equally justified in pointing out that this figure held in both the forward and reverse directions, something no conventional auto-reverse mechanism of the era could credibly claim. Technics described the RS-1700 not as an auto-reverse deck in the ordinary sense, but as a “two-way-forward” machine, a characterisation that is technically defensible and more than a little elegant.
The capstan motor is a quartz-controlled, phase-locked DC brushless direct-drive unit, building on the approach first used in the RS-1500US but incorporating newly developed integrated circuits for tighter management of phase, speed, and torque across varying load, temperature, and supply conditions. The two reel motors follow Technics’ direct-drive turntable philosophy, with reel-base and rotor integrated into a single assembly coupled to a fixed stator. This arrangement delivers consistent tape speed during fast-forward and rewind regardless of reel diameter, a meaningful practical advantage. Electronic tape tension control supplements the inherent stability of the Isolated Loop, working to suppress tension-induced modulation noise before it can occur rather than simply mitigating it after the fact.
The six-head configuration is another engineering commitment that sets the RS-1700 apart from simpler auto-reverse designs of the period. Rather than relying on a single set of heads pressed into service in both directions, the RS-1700 employs entirely separate head stacks for forward and reverse operation, each consisting of a Super Alloy laminated playback head with a 2-micron gap, a Super Alloy laminated recording head with a 10-micron gap, and a double-gap ferrite erase head. Switching between head sets is handled by a gold-clad twin-contact relay with a response time of around 0.1 seconds. The head assembly itself is a 24-pin plug-in unit designed for straightforward field replacement.
Reverse point detection is achieved entirely without mechanical contact with the tape. A 512Hz infrared LED beam, modulated at a quartz-controlled frequency, passes through the transparent leader tape at the end of a reel and falls on a matched photo-transistor configured to respond only to that specific intermittent frequency. This makes the system effectively immune to triggering from ambient light, a practical concern with older mechanical or simple optical detectors.
The amplifier section matches the transport in ambition.
The microphone preamplifier is a three-stage direct-coupled design achieving a dynamic margin of 75dB with the input attenuator at minus 20dB, a figure that compares favourably with many dedicated professional units of the same era. The recording amplifier employs an SEPP output stage with linearity extending to plus 28.5dB at 1kHz over the 0VU reference level, while THD at operating level is held to 0.8% across all three tape speeds. The bias oscillator runs at 120kHz and is supported by an independent constant-voltage circuit and dedicated power amplifiers, contributing to the stability of both the oscillation frequency and output level even as head assemblies are changed.
Transport logic is handled by a proprietary I²L (Integrated Injection Logic) integrated circuit, a then-current technology offering fast, reliable switching with minimal current draw. The Electro-Brake system applies reverse torque to the supply reel before engaging the mechanical brake when changing modes, reducing mechanical stress and improving tape safety. The time from any transport mode to play is stated at 0.7 seconds.
Operationally, the RS-1700 is well equipped. A real-time counter reads in minutes and seconds to plus or minus 1% accuracy at 15 ips. A cue lever maintains tape-to-head contact during fast-forward and rewind for easier programme location. An edit dial supports precision tape splicing using alignment points on the reversing roller. Pitch control allows speed variation of plus or minus 6%, roughly a semitone in either direction. Optional battery operation via the RP-086 adaptor extends the machine’s usefulness beyond fixed studio or listening room installations.
The RS-1700 was produced in an era when the serious audiophile open-reel market still commanded genuine engineering investment, and it shows. The machine’s combination of a mechanically rigorous bidirectional transport, a full six-head complement, quartz-locked direct-drive motors, and a capable amplifier section makes it a legitimate landmark in consumer tape recorder design, and one that has held its reputation well among collectors and enthusiasts of vintage analogue recording.
Features
- Isolated Loop tape path — single 34mm capstan with reversing roller and dual pinch rollers; symmetrical bidirectional transport
- Auto-reverse modes — three modes: Continuous (cont), Single-cycle reverse (rev), and Non-reverse (non rev)
- Photoelectric tape-end detection — 512Hz quartz-controlled infrared LED/filter/photo-transistor system; no mechanical contact with tape
- Six-head configuration — fully independent head stacks for forward and reverse; Super Alloy laminated record and playback heads, double-gap ferrite erase heads
- Plug-in head assembly — 24-pin connector; field-replaceable without soldering
- Gold-clad relay head switching — twin-contact relay; switching time approximately 0.1 seconds
- Quartz-locked direct-drive capstan motor — phase-locked DC brushless motor with newly developed ICs for phase, speed, and torque control
- Direct-drive reel motors — integrated rotor-platter design; consistent tape speed throughout fast-forward and rewind
- Electronic tape tension control — active tension regulation supplementing Isolated Loop; suppresses modulation noise at source
- I²L logic transport control — Integrated Injection Logic IC for fast, reliable mode switching
- Electro-Brake — reverse torque applied to supply reel before mechanical brake; mode-to-play time 0.7 seconds
- Microphone amplifier — three-stage direct-coupled design; 75dB dynamic margin at -20dB attenuator position
- Recording amplifier — SEPP output stage; linearity to +28.5dB at 1kHz; THD 0.8% at operating level
- Bias oscillator — 120kHz; independent constant-voltage circuit and dedicated power amplifiers
- 3-position bias and EQ selectors — independent selectors covering all major tape formulations
- Double-scaled VU meters — switchable between +6dB scale (S/N priority) and +3dB scale (linearity priority)
- Real-time tape counter — minutes and seconds readout; accuracy ±1% at 15 ips
- Cue lever — maintains tape-to-head contact during fast-forward and rewind
- Edit dial — precision tape editing and splicing using alignment points on reversing roller
- Pitch control — ±6% speed variation (approximately one semitone) in both record and playback
- Direction indicator lamps — built-in blinker lamps on forward/reverse keys; active in all transport modes including pause and stop
- Aluminium diecast chassis — motor housings integrated directly into precision diecast chassis
- Optional battery operation — via RP-086 adaptor
- Optional remote control — RP-9170