Bang & Olufsen Beocord 507 K

The Beocord 507 K is one of Bang & Olufsen’s very early post‑war tape recorders (around 1951), essentially a combined tape deck plus amplifier in the “Grand Prix 507K” family, aimed at domestic use rather than studio work.

Basic format and electronics

• Concept: Dedicated BeoCord tape recorder section built into, or designed to partner, the tube‑based Grand Prix 507K radio chassis.

• Amplification: Valve (tube) electronics using about seven valves in the host chassis (UCH21, UBF80, UAF42, UM4, UBL21, etc.), giving it a classic early‑1950s sound signature with modest power output.​

• Dynamics/noise: Listed “dynamics” around 55 dB, typical of early tape technology well before Dolby or high‑output tape formulations.​

Tape transport and performance

• Speed: A single domestic speed (typically around 9.5 cm/s / 3¾ ips) optimised for speech and general home recording, not wide‑band mastering.

• Frequency response: Approximately 50 Hz–8 kHz, which matches early paper‑oxide tape and simple head design; more than adequate for speech, but clearly limited vs. later hi‑fi standards.​

• Power consumption: Around 85 W in general use, 100 W when recording, and up to 120 W in reverse/rewind mode, reflecting a sizeable mains transformer and tube heaters.​

Connectivity and use

• Speaker connection: Provision for an external speaker of about 3.5 Ω, in addition to the main loudspeaker system in the associated radio/console.​

• Intended role: Part of a larger “Grand Prix” style domestic system – record radio programmes, family events, and occasional music, then play them back through the built‑in tube amplifier and speaker.

Practical and collector notes

• Sonic character: Warm, bandwidth‑limited, and noisy by modern standards, but with the distinctive tube coloration many collectors enjoy for period material.

• Restoration: Almost any surviving example will need full service – capacitors, rubber parts, and mechanical lubrication – but once restored it is an excellent historical piece showing B&O’s very early approach to tape.