The Ampex 350 Tape Recorder was introduced in 1953 as the successor to the Ampex Model 300. It quickly became one of the most widely used professional tape recorders of the 1950s, setting new standards for broadcast and studio recording.
The Ampex 350 was a two-speed magnetic tape recorder designed for use with standard 6.35 mm (¼-inch) tape and was available in console, rack-mounted, and portable configurations. Engineers could choose between full-track or half-track heads, and the unit was suitable for professional audio, broadcast, and laboratory applications.
The Ampex 350 built upon the reliability and sound quality of the Model 300 but introduced modular design and improved electronics. The tape transport and electronics were housed separately, simplifying maintenance and calibration.
With operating speeds of 9.5 cm/s and 38 cm/s (3¾ and 15 inches per second), it offered exceptional frequency response and low noise for its era. The frequency response at 38 cm/s extended from 30 Hz to 15 kHz within ±2 dB, providing clarity and detail that made it the studio standard of its time. Its signal-to-noise ratio reached 70 dB for full-track recording, with harmonic distortion kept under 3% at 400 Hz.
The Ampex 350’s instant start mechanism allowed the tape to reach full speed in less than 0.1 seconds, a key feature for broadcast cueing. It included four pushbuttons, Start, Stop, Fast Forward, and Rewind, plus a Record switch and equalisation controls for both NAB and RMA standards.
The unit’s flutter and wow performance was excellent for the period, at 0.2% at 38 cm/s. Engineers could operate it with NAB 26.7 cm (10½-inch) reels or smaller 12.7 cm (5-inch) and 17.8 cm (7-inch) reels, with adjustable tension for each. The machine’s separate record and playback amplifiers allowed simultaneous monitoring, and a 4-inch VU meter enabled precise level control.
The Ampex 350 became a mainstay in radio stations, recording studios, and early television production facilities worldwide. It was used by major broadcasters such as NBC, CBS, and the BBC. The model was known for its durability and serviceability, and its modular components made it a technician’s favourite. Many early stereo and multitrack experiments were also carried out using modified Ampex 350 units before the arrival of the 351 and 354 models in the late 1950s.
The Ampex 350 remains an important historical piece in the evolution of professional tape recording, representing a shift from experimental magnetic recorders to a mature, dependable technology that defined an era of analogue audio engineering.
Features
- Two speed 6.35 mm tape recorder available in console, rack mount, and two case portable versions
- Accepts full track or half track heads in a single plug in head housing
- Selectable tape speed pairs: 9.525 cm/s and 19.05 cm/s or 19.05 cm/s and 38.1 cm/s
- Instantaneous start to full speed in less than 0.1 seconds
- Four transport pushbuttons for Start, Stop, Fast Forward, and Rewind plus separate Record button
- Independent record and playback amplifiers for simultaneous monitoring
- Equalisation switch for proper amplifier equalisation at each speed
- Reel size switch for NARTB 266.7 mm reels and RMA 127 mm and 177.8 mm reels
- Record input selectable for microphone level low impedance or bridging 600 ohm +4 VU line, balanced or unbalanced
- Playback output at +4 VU into 600 ohms, balanced or unbalanced
- Phone jack monitoring with A B switch for source or tape, and 101.6 mm VU meter for level, bias, and erase current
- Approximate rewind time of one minute for a full 731.5 m reel
- Playback timing accuracy of ±0.2 percent
