Introduced in 1976, the Technics RS-9900US was a two-piece high-fidelity stereo cassette system comprising the Technics 9900 tape transport and a separate Technics 9900 record/reproduce amplifier. The system represented an extensive engineering effort to extend the performance limits of the compact cassette format, separating the mechanical transport from the recording and playback electronics so that each section could perform its specialised task without compromise. The two units were connected by multi-pole cables and could be installed together, separated for easier placement, or mounted in a professional equipment rack.
The tape transport of the Technics RS-9900US used a closed-loop, double-capstan system driven by three motors. An eight-pole, 24-slot direct-drive DC motor powered the external flywheel, while two coreless DC motors independently drove the supply and take-up reels. The closed-loop arrangement isolated the section of tape passing across the heads from external influences caused by the reels and cassette shell. Constant tape tension was maintained between the capstans, supporting stable tape-to-head contact, reduced modulation noise and low wow and flutter.
A flywheel extension also acted as the capstan over which the cassette pressure roller operated. The tape was pulled through the transport by the second capstan and flywheel assembly, while a closed-loop section remained mechanically decoupled from the supply and take-up reels. Technics stated that this arrangement reduced stress on the tape, minimised wear and helped prevent stretching during repeated use. The resulting transport achieved a specified wow and flutter figure of 0.04% WRMS.
The three-head configuration of the Technics RS-9900US used separate recording, playback and erase heads, allowing the recorded signal to be monitored directly from the tape during recording. Technics developed HPFTM record and playback heads for the RS-9900US, with the design intended to provide long service life and suitable electrical characteristics for a three-head cassette system. With chromium dioxide tape, the machine achieved a specified frequency response of 25Hz to 20kHz within ±3dB.
The playback head azimuth could be adjusted by the user. A built-in 8kHz oscillator allowed a test signal to be recorded and monitored from the playback head while the azimuth was adjusted for optimum high-frequency response. A small screwdriver was supplied for making this adjustment, providing a practical means of compensating for alignment differences between tapes and recording equipment.
Transport operation was controlled by feather-touch sensor buttons operating through solid-state switching and integrated logic circuits. The transport could change directly from one operating mode to another without requiring the user to press stop first. The buttons used a short operating stroke, while the electronic control system eliminated conventional mechanical switching between transport functions.
The direct-drive capstan motor also permitted variable playback speed. Pitch control provided an adjustment range of ±5%, allowing the playback pitch to be altered by approximately half a musical tone in either direction. This could be used when tuning another instrument to a recording or when matching the pitch of existing material.
A dedicated tape-time meter estimated the remaining playing time in minutes. Scales were provided for C-90, C-60, C-45 and large-hub cassette formats. The system monitored the speed of the supply reel motor and translated it into an indication of remaining programme time.
Memory rewind and memory play functions were also provided. After rewinding, the transport could stop automatically at a selected tape-counter position or resume playback from that point. An optional timer connection allowed radio programmes to be recorded automatically or enabled playback to begin at a preset time.
The separate record/reproduce amplifier incorporated independent recording and playback circuitry. The microphone amplifier provided a claimed dynamic range of 55dB at -72dB sensitivity and used a two-stage direct-coupled circuit with low-noise PNP transistors and low-noise metal-film resistors. The recording amplifier used another two-stage direct-coupled design and incorporated bass equalisation.
The playback amplifier used high-grade selected components, including tantalum capacitors, within a signal-to-noise ratio design specified at 132dB against referenced input. The system used transistor switching throughout the signal path, avoiding mechanical switches and relays that could introduce contact noise.
The Technics RS-9900US provided extensive adjustment facilities for matching different cassette formulations. Separate calibration controls were available for Dolby playback level, Dolby recording level, bias current and recording equalisation. The bias and equalisation selector included fixed settings for standard tape types and a variable position that allowed both parameters to be adjusted using the calibration controls.
Bias current could be varied from -50% to +100% relative to the standard setting. Recording equalisation could be adjusted independently for the left and right channels, while the Dolby recording and playback levels could be matched to the sensitivity of the tape being used. Built-in 400Hz and 8kHz oscillators supplied the reference signals required for level, bias and azimuth adjustment.
Tape selection accommodated normal, chromium dioxide and ferrichrome formulations. The oscillator section provided switchable 400Hz and 8kHz test tones, while the Dolby noise reduction section included dedicated recording and playback processing. An MPX filter prevented 19kHz and 38kHz FM stereo carrier leakage from interfering with Dolby tracking when recording FM broadcasts.
Two illuminated peak-reading meters were designed to meet professional measurement standards. Their response characteristics were specified with rise times of 10ms for -1dB and 3ms for -4dB. Four operating-amplifier integrated circuits were used for the meter-driving circuitry.
Recording levels were controlled by separate microphone/auxiliary and line-input controls. A two-gang detented output-level control allowed repeatable settings in 2dB increments. The front panel also provided microphone inputs, an auxiliary input and output, a headphone connection with a dedicated amplifier, source and tape monitoring, a recording indicator and microphone attenuation.
The microphone attenuator reduced gain by 30dB, allowing the microphone inputs to accommodate higher sound-pressure levels. The dedicated headphone amplifier was designed to drive a wide range of headphone impedances. Additional input and through-output connections were located within the cassette compartment for temporary access, while the main amplifier also provided rear-panel signal connections.
The transport and amplifier each carried a functional block diagram and circuit information on the top panel for convenient reference. The optional Technics RP-9690 remote-control unit provided wired control of the principal transport functions.
The Technics RS-9900US remained in production until approximately 1980. Its separate transport and amplifier architecture, three-motor closed-loop mechanism, three-head monitoring system and extensive calibration facilities placed it among the most technically elaborate cassette recording systems produced during the format’s analogue era.
Features
- Separate tape transport and record/reproduce amplifier units
- Closed-loop double-capstan transport
- Three-motor drive system
- Direct-drive capstan motor
- Independent coreless supply and take-up reel motors
- Three-head recording, playback and erase configuration
- HPFTM recording and playback heads
- Off-tape monitoring during recording
- User-adjustable playback-head azimuth
- Built-in 400Hz and 8kHz test oscillators
- Full integrated-logic transport control
- Feather-touch transport controls
- Direct switching between transport modes
- Variable playback pitch control
- Tape-time meter displaying estimated remaining programme time
- Memory rewind and memory play functions
- Timer-controlled recording and playback
- Normal, chromium dioxide and ferrichrome tape compatibility
- Variable bias and recording equalisation
- Independent left and right recording equalisation adjustment
- Dolby recording and playback level calibration
- Dolby noise reduction
- MPX filter for recording FM stereo broadcasts
- Illuminated peak-reading level meters
- Detented output-level control with 2dB steps
- Separate microphone, auxiliary and line-input level controls
- 30dB microphone attenuator
- Dedicated headphone amplifier
- Source and tape monitoring
- Auxiliary input and output connections
- Optional Technics RP-9690 wired remote control
- Professional rack-compatible construction