Nagra IV-S

The Nagra IV-S (Stereo) is widely regarded as the pinnacle of portable analog recording technology. Manufactured by Kudelski S.A. in Switzerland starting in 1971, it was the first stereo recorder in the legendary Nagra IV series. Designed originally for high-end film and television field production, its robust engineering and sonic transparency eventually made it a favorite for audiophile location music recording.

The Nagra IV‑S became a de‑facto standard in cinema production from the 1970s onward. It combines extremely precise mechanical transport with very low‑noise mic preamps, robust timecode/pilot options, and exceptional build quality in a field‑ready package.

Transport and tape format

The IV‑S is a 6.35 mm (¼‑inch) analogue recorder using two main audio tracks plus a narrow center track. The center track carries pilot or time‑code information and can also serve as a cue track in some variants.​

• Standard two‑track stereo format, with each audio track about 2 mm wide on pilot versions.​

• Center track used for Neopilot or FM timecode (Nagra Master / TC variants), or as a low‑fi cue track.​

• Normally supplied for 5‑inch reels as a portable field machine; accessories allow use of 7‑inch reels with an extended lid and reel adapter.

Speeds and equalization

The IV‑S supports multiple speeds oriented to film and broadcast work. Nagra also offered its proprietary “Nagra Master” equalization mode for improved high‑frequency response and lower noise at moderate speeds.​

• Typical speed set: 15 ips and 7.5 ips, with some machines also offering 3.75 ips.​

• “15 ips Nagra Master” mode uses 15 ips transport with an EQ contour similar to 7.5 ips to optimize HF extension and noise while remaining compatible with studio repro chains aware of the curve.​

• Equalization switchable between international standards (e.g., NAB/CCIR) depending on market and version.​

Audio electronics and signal path

The IV‑S was the first stereo Nagra and is built around very high‑quality, low‑noise analogue electronics tailored to dialogue and music recording. Its mic preamps and limiters are a big part of its reputation among location recordists and some audiophiles.​

• Two independent microphone input channels with transformer‑balanced inputs, adjustable gain, and high‑quality preamplifiers.​

• Dual level controls (pots) for precise left/right balance and gain setting.​

• Built‑in limiters on each channel with carefully designed attack/release to protect against overloads in unpredictable field conditions.​

• Switchable line‑level inputs and monitor outputs, including headphone and line monitoring from source (pre‑tape) or off‑tape playback head.​

• Modulometer (Nagra’s combined VU/peak meter) with a reference point calibrated hotter than many studio decks (often about +8 dB relative to conventional “0” VU) to exploit tape headroom.

Synchronization and timecode

A core reason for the IV‑S’s dominance in film production is its sync capability. Several variants exist depending on synchronization standard and era.​

• Standard IV‑S uses a center pilot track to record a 50/60 Hz Neopilot sync tone derived from the camera, ensuring speed lock between picture and sound.​

• Later IV‑S models introduced a 14 kHz FM‑modulated sync/timecode signal on the center track, which differs from older Neopilot and is not backward‑compatible.​

• Timecode‑capable versions (IV‑STC, IV‑S TC) provide full SMPTE/EBU timecode handling for modern post‑production workflows of the late analogue era.

Power, build, and field use

The IV‑S is engineered as a rugged, serviceable field machine rather than a studio console deck. Its mechanical precision and reliability helped establish Nagra’s reputation in broadcast and film circles.​

• Typically powered by 10 D‑cell batteries in a removable tray, with options for external DC supplies for longer shoots or studio use.​

• All‑mechanical tape transport with a capstan and carefully tensioned supply/take‑up system using multiple rollers, a stabilizer roller near the record head, and a clutch lever that opens the tape path for threading.​

• Transport controls via a main function selector bar and separate rewind/fast‑wind control, with tape path designed to minimize head wear and tape damage when correctly threaded.​

• Chassis built as a compact, over‑engineered metal enclosure with sealed controls and modular internal boards, intended to survive field abuse and be maintainable by authorized service centers

Typical applications and sonic character

In practice the IV‑S served as the reference portable recorder on countless film sets and documentary shoots, and it still finds use in archival and audiophile contexts. Its sound is often described as clean but characterful, with very stable imaging and low modulation noise for a portable machine.​

• Primary use: sync‑sound recording for cinema, television, and documentary, often paired with crystal‑sync cameras.​

• Secondary use: high‑quality stereo music and ambience recording, particularly in classical and location‑based projects where portability and reliability are critical.​

• Sonically, users report a tight, precise low end, smooth midband, and slightly “sweet” top depending on tape, speed, and EQ, with performance that remains competitive with many studio quarter‑inch decks despite the portable form factor.