Released in 1985, the Tandberg TCD 910 was a professional master cassette recorder designed to replace reel-to-reel and cartridge machines in applications where physical tape editing was not required. It represented the professional model in Tandberg’s TCD 900 series and combined a three-motor transport, three independent heads, balanced connections and extensive microprocessor control within a purpose-built cassette mastering system. Rather than adapting a domestic cassette deck for studio use, Tandberg developed the TCD 910 around the operational requirements of broadcasters, recording facilities, duplicating rooms and other professional environments.
The Tandberg TCD 910 used an 8-bit microprocessor supported by 32K of EPROM memory. This control system governed an unusually extensive range of transport, cueing, timing, search and programming functions. Recordings could be started directly from playback using the flying-start recording facility, while pauses could be inserted manually or automatically for later use by the deck’s search and cueing functions. The transport also allowed transitions between operating modes without requiring the user to return the machine to stop first.
The cassette was mounted directly onto the transport hubs rather than being placed behind a conventional hinged cassette door. Tandberg stated that this arrangement provided consistent and accurate cassette positioning. A protective cover enclosed the cassette during operation, while the RELEASE control returned the transport to its loading position so that the cassette could be removed. After fast winding reached the end of the tape, the transport automatically returned to the release position.
The transport included separate controls for release, rewind, fast forward, play, stop and record. A short press on either winding button moved the tape slowly, while holding the control engaged full-speed winding. PLAY could be selected from other operating modes, including rewind, fast forward, stop and record. When switching directly from playback or record to stop, the heads remained in their operating position to minimise the delay involved in returning to playback or recording.
The RECAP function provided an additional cueing method. Pressing PLAY and STOP together during playback allowed the tape to rewind slowly while its audio remained audible. Releasing the controls returned the deck to playback, allowing an operator to locate a precise point for flying-start recording, dubbing or programme cueing.
Recording could be initiated in several ways. Pressing RECORD alone placed the machine into record mode from stop, while RECORD and PLAY could be used together as an alternative start method. Recording could also begin directly from playback by holding RECORD and pressing PLAY, allowing a new recording to begin without first stopping the transport. This facility was intended for applications requiring rapid and accurately positioned recording starts.
The Tandberg TCD 910 also provided several methods for recording pauses. Holding RECORD while pressing STOP briefly inserted a four-second muted section and then stopped the transport. Longer pauses could be created by holding both controls for the required period. A pause could also be placed at the beginning of a recording by holding STOP and RECORD while briefly pressing PLAY. Depending on which control was released first, the machine would either continue recording or return to stop.
A multi-mode electronic display served as both a conventional tape counter and a real-time counter. In its basic mode it displayed arbitrary counter numbers, with one counter counting upwards and another downwards towards zero. Once the cassette had passed through the calibration routine, the TCD 910 measured the tape thickness and calculated the current position in actual playing time. Holding the CAL/SET button for more than two seconds initiated calibration, during which the transport briefly moved the cassette before calculating the installed tape length.
The display could identify commonly used cassette lengths, including C-60, C-90 and C-120, while other tape lengths could be selected manually. Once calibrated, the counter could be reset to zero at the beginning of the tape and used to show the elapsed or remaining programme time. During rewind past zero, the counter displayed negative values so that the operator could see how far the tape had moved beyond its reference position.
The counter and memory system allowed programmed stopping points to be stored as addresses. Up to ten addresses could be retained in memory, with an additional stopping point available through the stop position. Each address was associated with a counter value, allowing the transport to locate predetermined positions on the cassette. Addresses could be entered during playback or recording without interrupting the programme, or entered manually when preparing a new tape.
The Cue Points selector allowed the stored addresses to be reviewed and recalled. In its number position, the display showed the address currently selected, while the winding controls moved through the address register. Pressing the rewind and fast-forward controls together displayed the counter value stored under the selected address. Moving the selector to GTO instructed the transport to wind to that programmed location.
Programme searching could also be performed from pauses recorded between selections. With the Search selector set to Cut No., the deck counted recorded gaps of at least four seconds and used them to locate individual programmes. When the selected programme was found, the tape stopped approximately one second before its beginning and then entered either stop or play, depending on the selected operating mode.
The Cueing position allowed the programme content to remain audible during winding at approximately one quarter of normal winding speed. This provided another method of finding programme starts or specific recorded passages. The search system could also operate in conjunction with stored programme numbers, allowing an operator to locate material through either recorded pauses or programmed addresses.
The Cut selector controlled how the TCD 910 responded when pauses were detected. In its stop position, the transport stopped when the selected pause was found. If the pause continued beyond four seconds, the audio was muted and the machine advanced towards the next programme, stopping about one second before its beginning. If a pause exceeded approximately 30 seconds, the machine entered stop after that interval.
The Cut selector could also operate while recording. If no programme appeared at the input for approximately 20 seconds, the transport stopped automatically. Its BOT, or Beginning of Tape, setting rewound the cassette to its beginning when the machine encountered a pause of at least four seconds during playback. This function was not available during recording.
The Tandberg TCD 910 accommodated Type I normal, Type II high-bias and Type IV metal cassettes. Automatic equalisation selection operated for properly coded cassette shells, although equalisation could also be selected manually when required. The tape selector and calibration controls allowed the recording system to be optimised independently for different formulations.
Each of the three principal tape groups had individual left- and right-channel adjustments for bias current and recording current. These adjustments were accessed through twelve recessed controls located around the tape selector. Six controls adjusted bias for the two channels across the three tape groups, while the remaining six adjusted recording current. This allowed frequently used cassette formulations to receive their own stored calibration settings.
A continuously variable record-head azimuth control was provided for recording alignment. Tandberg recommended checking azimuth whenever the cassette formulation changed and whenever switching to another cassette, even when the same tape type was used. Correct adjustment was obtained by comparing the two peak-reading meters and setting the azimuth for the highest and most stable indication on both channels.
The deck generated internal 315Hz and 15kHz calibration tones through the Monitor/Test selector. The 315Hz signal was used to set recording current, while the 15kHz signal was used for bias adjustment. The operator first adjusted both channels to the same reference level with the 315Hz tone, then selected 15kHz and adjusted bias until the meter readings matched the low-frequency reference. The source position returned the machine to normal recording operation.
The calibration arrangement allowed the user to favour different performance priorities. Following Tandberg’s recommended procedure produced an extended high-frequency response, although alternative bias settings could trade some frequency extension for reduced distortion or increased headroom. The recording system could therefore be adjusted according to the requirements of the tape stock and programme material.
Separate record and playback heads allowed off-tape monitoring during recording. With the Monitor/Test selector set to Source, the operator heard the incoming signal before it reached the tape. Selecting Tape routed the signal reproduced immediately from the recorded cassette through the playback head. This enabled the original and recorded signals to be compared while recording was in progress.
The monitoring system was intended to reveal incorrect levels, excessive distortion, tape noise, poor azimuth adjustment, an unsuitable tape setting, incorrect calibration, contamination within the tape path or inadequate cassette quality. Since the recorded signal could be checked immediately, problems could be identified before the recording session was completed.
Two illuminated peak-reading meters displayed the actual recording current. The scales extended from above +6dB to -20dB and included the normal 0dB reference point. A separate M marking above +3dB provided the recommended reference point for metal tape, reflecting its ability to accept a higher recording level than conventional oxide formulations.
The main input-level control adjusted both channels simultaneously and was calibrated from +12dB to -30dB, with 0dB positioned at the top of the control. A concentric reference marker allowed a setting to be identified and recalled. A separate balance control adjusted the relationship between the left and right channels.
Dolby B and Dolby C noise reduction were selectable from the front panel. Tandberg advised using Dolby C when greater signal-to-noise performance was required and ensuring that the same Dolby system was selected during playback as had been used when the cassette was recorded. The TCD 910 also provided a front-panel headphone output with its own level control.
Professional audio connections were fitted to the rear panel. The left and right inputs used electronically balanced female XLR connectors, while the outputs used electronically balanced male XLR connectors. Each output channel could be calibrated independently so that a tape reference flux level of 250nWb/m corresponded to an output level between -2dBu and +12dBu.
A 25-pin remote-control connection allowed the deck’s principal functions and indicators to be integrated into an external control system. Functions were activated by connecting the relevant pins to ground. Transport commands, operating modes and associated LED indications were available through the connector, allowing the TCD 910 to be incorporated into broadcast, studio or duplication installations.
An optional cable remote provided direct access to commonly required transport and search functions. The RC 900 remote specified for the TCD 910 included play, stop, record, rewind, fast forward, space, recap, Cut No. and cue controls. Tandberg also offered an optional 19-inch rack-mounting kit, transformer-balanced input and output electronics, a computer audio interface, an RS-232 data interface, side panels and an acrylic cover. Special-order accessories included an infrared remote-control system and custom software control packages.
The TCD 910 employed three motors and three tape heads. Contemporary measurements confirmed peak wow and flutter of 0.09 per cent and a WRMS result of 0.038 per cent. Speed accuracy was measured at -0.262 per cent, within Tandberg’s stated tolerance of ±0.5 per cent. Fast rewind time for a C-60 cassette was measured at 34 seconds.
Measured frequency response reached 20Hz to 25kHz with Type I tape without Dolby processing and 20Hz to 23kHz with Dolby B or C. Type II tape measured 20Hz to 25kHz without Dolby and 20Hz to 21kHz with Dolby engaged. Metal tape measured 20Hz to 23kHz with Dolby B or C. Measured signal-to-noise ratios with Dolby C reached 72.6dB for Type I tape, 80.9dB for Type II and 80.4dB for metal tape.
The TCD 910’s maintenance procedures reflected its professional operating role. Tandberg recommended frequent cleaning of the heads, guides, capstans and pinch rollers, particularly when the machine was used daily. The tape path could be exposed by placing the transport in its cleaning position, and the heads were to be cleaned with isopropyl alcohol. The pinch rollers were to be cleaned with a cloth moistened with water rather than solvent.
Demagnetisation of the tape path was also recommended if audible background noise increased. The procedure involved switching the recorder off, moving the demagnetising tool slowly around the tape heads and guides without making contact, and withdrawing it to a distance of at least 1 metre before switching it off.
With its microprocessor-controlled transport, programmable counter, search facilities, real-time display, direct cassette mounting, comprehensive tape calibration, three-head monitoring and balanced professional connections, the Tandberg TCD 910 extended the compact cassette into applications normally associated with larger recording formats. Its design treated the cassette as a professional recording medium and provided the operational control needed for mastering, broadcast, duplication and programme production.
Features
- Professional master cassette recorder
- Three-head recording and monitoring system
- Three-motor tape transport
- 8-bit microprocessor control with 32K EPROM memory
- Direct cassette mounting system
- Flying-start recording from playback
- Real-time and conventional counter modes
- Automatic tape-length calibration
- Programmable stopping-point memory
- Up to ten stored cue addresses
- Programme search using recorded pauses
- Audible slow-speed cueing
- RECAP audible rewind function
- Automatic pause insertion
- Automatic beginning-of-tape return
- Type I, Type II and Type IV cassette compatibility
- Automatic or manual equalisation selection
- Independent left- and right-channel bias adjustment
- Independent left- and right-channel recording-current adjustment
- Continuously variable record-head azimuth adjustment
- Internal 315Hz and 15kHz calibration tones
- Source and off-tape monitoring
- Illuminated peak-reading meters
- Separate metal-tape recording reference marks
- Dolby B and Dolby C noise reduction
- Balanced XLR inputs and outputs
- Adjustable professional output calibration
- Front-panel headphone output with level control
- 25-pin remote-control interface
- Optional cable and infrared remote controls
- Optional 19-inch rack-mounting kit
- Optional transformer-balanced audio interface
- Optional RS-232 data interface