Bang & Olufsen Beocord 509 K

The Bang & Olufsen Beocord 509 K is an early 1950s valve-based tape recorder/amplifier unit (Type T 509 K), paired with the companion Beocord T 509 U transport, marking one of B&O's initial forays into domestic open-reel recording around 1954.

Format and Transport

• Tape format: ¼-inch tape at a single domestic speed of 9.5 cm/s (3¾ ips), optimized for speech and basic music; mono operation.

• Heads: Basic dual-head setup (record/playback combined, plus erase head) typical of post-war consumer designs.

• Motors: Simple single-motor capstan drive with manual reel loading; no auto-reverse or advanced tensioning.

Electronics and Performance

• Amplification: Tube/valve electronics (around 7–10 valves in the 509 K chassis) for warm sound, integrated with radio/console systems like the Grand Prix series.

• Specs: Frequency response ~50 Hz–8 kHz; dynamics/noise ~55 dB; power draw 85–120 W depending on mode.

• Inputs/outputs: Mic, radio/phono inputs; external speaker output (~3.5 Ω).

Physical Design

• Form: Separate transport (509 U) and amp unit (509 K) for modular setup in furniture consoles; compact for the era but heavy due to transformers.

• Build: Teak or rosewood cabinets emphasizing Danish aesthetics over raw performance.

Context

This pre-stereo model precedes later Beocords like the 507 K or Belcanto, prioritizing reliability and integration in home systems over hi-fi specs; today valued for historical tube tone rather than bandwidth, with restoration focusing on caps and lubricants.