Philips EL3505

The Philips EL3505 is an early‑1950s professional mono broadcast reel‑to‑reel recorder, essentially a large studio machine derived from pre‑war German tape technology rather than a domestic deck.​​

Position and era

• Introduced around 1950 as one of Philips’ first broadcast‑grade tape machines, used in studios and radio facilities rather than homes.​​

• Physically and mechanically it closely resembles the AEG K4/K8 lineage: heavy deck, large open transport, and substantial metalwork.​

Mechanical layout and tape transport

• Two‑part system:
  A main tape deck section containing the transport, heads and basic controls.
  A separate electronics / amplifier cabinet that houses the power supply and audio circuitry, linked via multicore cables.​

• Designed for high‑speed operation, with tape speeds up to 30 ips (30 inches per second) for top‑grade transient response and low noise on critical programme and effects work.​

• Uses ¼‑inch tape on large professional reels (NAB/AEG‑style hubs), handled by a robust capstan and reel‑motor assembly intended for continuous duty.

Head configuration and audio format

• Full‑track mono headblock: one wide track across the tape for maximum signal‑to‑noise ratio, entirely in line with early broadcast practice.

• Standard three‑head configuration for the era (erase, record, playback) is typical for this class, enabling off‑tape monitoring and easier alignment, although detailed head specs for the EL3505 are sparse.

Electronics and connectivity

• All‑valve (tube) signal path in the separate electronics rack, with:
  Record and replay amplifiers optimized for line‑level I/O into studio consoles.
  Fixed, standardized equalization for broadcast use.

• Balanced‑type connections (via multi‑pin connectors) were normally used to tie the recorder into studio patch bays and mixers.

Operational role and usage

• Intended as a studio workhorse: high‑speed recording of music, speech, and sound effects where tape cost and run‑time were less important than quality.

• The two‑cabinet design, high tape speeds, and full‑track format make it very different from later Philips domestic machines (EL35xx/EL36xx) that ran 7½/3¾ ips on small reels with built‑in speakers.

Because documentation is scarce, a lot of what’s known about the EL3505 comes from surviving units and period comparisons; if you’re looking at restoration or purchase, treat it as a heavy, high‑speed, valve studio deck in the AEG K‑series tradition rather than anything remotely “hi‑fi domestic.”