Ampex 351

The Ampex 351 reel-to-reel tape deck is a high-fidelity professional tape recorder produced between 1958 and 1961, evolving from the earlier Ampex 350 model. It features tube-based electronics and is designed primarily for studio and mastering applications, offering a refined and precise recording and playback experience.​

Key technical specifications and features include:

• Tape format: ¼ inch magnetic tape on reels up to 10.5 inches (NAB standard), with reel size selection for proper tensioning.

• Tape speeds: Supports 15 ips and 7½ ips primarily, optimized for broadcast and professional use.

• Head composition and arrangement: Three permalloy heads configured for half-track mono operation with options for full or half-track configurations, allowing high-quality recordings with excellent signal-to-noise performance around 60 dB full track.

• Frequency response: Approximately 30 Hz to 15 kHz within ±2 dB at 15 ips.

• Wow and flutter: Exceptionally low, under 0.15% RMS at 15 ips and under 0.2% RMS at 7½ ips, assuring stable tape transport and minimal distortion.

• Amplifier and electronics: Features a four-stage high-gain record amplifier using dual triode tubes (such as ECC83/12AX7, 12AU7, 12AT7) delivering strong input sensitivity, selectable balanced or unbalanced inputs, and outputs with ±8 dBm output levels.

• Controls: Pushbutton operation for PLAY, STOP, FAST FORWARD, REWIND, and RECORD; electrical interlocks prevent operational errors; includes tape speed switching and reel size tension control.

• Mechanical transport: Three motors for capstan, take-up, and rewind with solenoid-driven idler for capstan traction; fast start time (~0.1 sec), fast stop, and precise tape tension control eliminate tape wear and reduce flutter.

• Dimension and weight: Approximately 48" high × 29" deep × 25" wide, weighing about 168 lbs including console.​

The Ampex 351 was renowned for its reliability, sound quality, and ease of maintenance, aided by modular electronic assemblies and rugged build quality. It was favored for mastering and broadcast work, evidenced by its use in notable remastering projects and its enduring reputation among vintage tape equipment collectors.​

In summary, the Ampex 351 represents a mature refinement of mid-century tape recorder technology, balancing mechanical precision with sophisticated tube electronics to deliver a professional-grade deck ideal for high-fidelity analog recordings. Manuals and detailed service documentation remain accessible for users aiming to maintain or restore these devices.​