Philips EL3547

The Philips EL3547 (also known as RK36 in some markets or variants like EL3547A /00, /22, etc.) is a landmark early 1960s consumer reel-to-reel tape recorder, introduced around 1962 and produced for several years into the mid-1960s. It marked a significant advancement for Philips' domestic line as one of their first fully transistorized (solid-state) models, moving away from vacuum tubes prevalent in earlier EL35xx series like the EL3542.

This was a stereo four-track (quarter-track) machine with true stereo recording and playback capabilities—quite forward-thinking for the era when many consumer decks were still mono or had limited stereo features. It included built-in dual speakers for self-contained operation, sound-on-sound (multiplay) overdubbing, and a symmetrical, aesthetically pleasing design that emphasized balance in controls and appearance.

Key Technical Specifications

• Recording/Playback System — Four-track (quarter-track) stereo; records and plays in both directions (tracks 1-4 forward, 3-2 reverse); supports stereo record/playback and mono compatibility.

• Tape Speeds — Two speeds:1⅞ ips (4.75 cm/s)
  3¾ ips (9.5 cm/s) (No 7½ ips or higher professional speeds; focused on compact, affordable home use.)
  

• Reel Size — Maximum 6 inches (15 cm) diameter (some sources note 15 cm exactly; smaller than the 7-inch reels common in later models like N4400 series).

• Frequency Response (approximate, within typical tolerances like ±3–6 dB; varies by source and tape condition):At 3¾ ips (9.5 cm/s): 50 Hz – 13,000–15,000 Hz (some claims up to higher, but realistic ~60 Hz – 13 kHz)
  At 1⅞ ips (4.75 cm/s): 60 Hz – 10,000 Hz (or ~60–10 kHz) Performance was good for a consumer transistor machine of the time, especially with quality tape.
  

• Wow & Flutter — Not precisely documented in most sources, but typical for era: around 0.2–0.3% at 3¾ ips (respectable; belt-drive mechanism contributed to smooth operation).

• Signal-to-Noise Ratio — Around 45–50 dB (solid for early transistor decks; better than many tube contemporaries due to lower noise floor).

• Heads — Typically 2-head configuration (combined record/playback head + erase head); permalloy construction.

• Drive System — Single motor with belt drive to the flywheel/capstan; innovative belt-shifting mechanism (via push-buttons) to switch between pulley grooves for the two speeds; no separate capstan motor or 3-motor design.

• Electronics — Fully transistorized (germanium transistors in early units, e.g., AC107 series; 13 transistors total in some variants); no power transformer—instead, extra windings on the drive motor supplied power to the amplifiers (clever space/cost-saving design).

• Amplification & Speakers — Built-in stereo power amplifiers with two end stages, each ~1.5–3 W; dual built-in loudspeakers (~3 W total output); tone control, balance knob, recording level controls.

• Inputs — Microphone (low-level); line/radio/phono (higher level); likely DIN-style connectors common in European Philips gear.

• Outputs — Line out for external amp; headphone possible; internal speakers for direct monitoring.

• Features —Sound-on-sound / multiplay (bounce tracks for overdubbing).
  Automatic tape-end stop during record/playback.
  Fast wind/rewind (~900 feet / 260 m in reasonable time).
  Pause function.
  Track selector.
  Magic eye or level meter for recording (some variants).
  Symmetrical control layout for visual balance.
  

• Power — AC mains (110/127/220/245 V switchable depending on region/model); no battery option.

• Build & Dimensions — Portable/tabletop case with lid and carry handle; dimensions approx. 39 × 33 × 18 cm (15.4 × 13 × 7.1 inches); weight around 9–10 kg (lighter than tube predecessors due to transistors).

• Manufacturing — Made in Eindhoven, Netherlands (or related Philips facilities); some regional variants (e.g., Maestro 40 rebrand).

Performance & Legacy Context

Launched in 1962, the EL3547 was hailed as a breakthrough: fully transistorized when tubes still dominated, true stereo four-track recording/playback, built-in speakers, and overdub capability—all in a compact, symmetrical package. It excelled for home music recording, radio dubbing, and family use, offering better noise performance and reliability than tube models like the EL3542 (which was mono, tube-based, supported up to 7" reels in some configs, and had different speeds).

Compared to the EL3542 (tube, often mono or limited stereo, higher speeds possible), the EL3547 prioritized portability, stereo, and modern solid-state tech over raw fidelity or larger reels. Common modern issues include hardened belts (main drive belt often slips and needs replacement), aging germanium transistors, dried capacitors, and mechanical wear—restorations can revive them nicely, with good sound through external amps.