IV-S

About the IV-S

The Nagra IV-S is a portable stereo 6.35-mm (¼ inch) analogue audio tape recorder introduced in the 1970s by Nagra Audio, designed for high-quality musical recording and professional film and television applications. It supports three tape speeds: 15, 7½, and 3¾ ips (38, 19, and 9.5 cm/s) with NAB, CCIR, and NAGRAMASTER equalization standards. The machine has two 2-mm audio tracks and a central track for pilot tone or time code, depending on the version (NQS-LSP non-pilot or NQS-TC time code). It features two microphone preamplifiers switchable between dynamic, T (+12V), or P (+48V) condenser with phase reversal, or two current line inputs. The recorder includes separate recording and playback heads for confidence playback, a built-in monitoring speaker switchable between source or tape, a reference generator, modulometer, alarm indicators for power supply and tape transport, and provisions for external noise reduction systems. It also incorporates a patented anti-distortion circuit, high-pass filters to reduce low-frequency resonance, and switchable automatic level control and limiter. Power can be supplied by internal batteries (12 D cells) or an external supply (ATN-4). The IV-S can accommodate tape reels up to 7 inches with optional expansions for 10-inch reels. It is known for its excellent microphone preamps, large dynamic range, and reliability. The IV-S was widely used in professional audio recording, including notable music albums and film soundtracks, and remains a reference for audio quality and durability despite being discontinued.