The UHER SG-631 LOGIC: Mastering Precision

The UHER SG-631 LOGIC, launched in 1979, is a semi-professional reel-to-reel tape recorder that sets a high standard in its class. Equipped with a computer-controlled, 4-motor drive system, this machine offers both 2- and 4-track operation, making it versatile for various recording needs.



The SG-631 introduces a cutting-edge OMEGA-DRIVE tape transport system, eliminating the need for a pressure roller, ensuring smoother tape handling, and reducing wear. The tape tension is electronically controlled, maintaining consistency across all operations, while the innovative design allows for easy swapping of tape head carriers, letting users switch between 2- and 4-track configurations effortlessly.

Precision is key with the SG-631. It features a speed fine-tuning mechanism, adjustable within +/- 4%, and a limiter that prevents distortion during short-term peaks. The unit also offers pre- and post-tape monitoring, allowing you to compare the incoming signal with the recorded output in real-time.

The machine supports three tape speeds—19, 9.5, and 4.75 cm per second—with the 9.5 cm/sec setting still meeting HiFi DIN standards, and 4.75 cm achieves a frequency response of 20-12,500 Hz. Large 26.5 cm reels can be used, holding up to 1,280 meters of tape, which can be rewound in just 120 seconds. A built-in stereo headphone amplifier allows for independent listening, while the control system enables the mixing of two microphones and two other sound sources simultaneously.

Additional features include a mute switch to eliminate noise during switching, playback head fine adjustment for high-quality playback of third-party recordings, and a cueing facility to easily locate the right tape position.