Stereoscope Type No. 555

HMV (Brand), His Masters Voice, The Gramophone Company Ltd.; Middlesex

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  • Year
  • 1959 ?
  • Category
  • Audio Amplifier or -mixer
  • Radiomuseum.org ID
  • 367342

Click on the schematic thumbnail to request the schematic as a free document.

 Technical Specifications

  • Number of Tubes
  • 13
  • Number of Transistors
  • Main principle
  • Audio-Amplification
  • Wave bands
  • - without
  • Details
  • Hi-Fi equipment
  • Power type and voltage
  • Alternating Current supply (AC) / 50/60 Hz, 100/120; 200/250 Volt
  • Loudspeaker
  • - This model requires external speaker(s).
  • Power out
  • 20 W (undistorted)
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: Stereoscope Type No. 555 - HMV Brand, His Masters Voice,
  • Shape
  • Book-shelf unit.
  • Dimensions (WHD)
  • 14 x 4 x 13.5 inch / 356 x 102 x 343 mm
  • Notes

  • The Stereoscope 555, stereo valve amplifier introduced in 1959, manufactured by Scientific & Technical Developments Ltd. (S.T.D. Ltd.)., Wallington, Surrey and marketed by E.M.I. Sales & Service Ltd., Hayes under the Emisonic name. The unit provides two fully independent preamplifier channels with separate input selectors, tone controls and volume controls, feeding a pair of EL84 ultralinear push‑pull power amplifiers. Facilities include steep‑cut and rumble filters, loudness compensation, multiple stereo/mono routing modes, and a built‑in oscilloscope‑type indicator (1CP1) for calibration, balance and output‑level monitoring.

    Technical Data

    • Power output: 10 W per channel 
    • Frequency response: 20 Hz–20 kHz ±1 dB
    • Crosstalk: >30 dB (30 Hz–15 kHz)
    • Inputs: Radio, Microphone (two sensitivities), Tape Head, LP/Col./78 (magnetic or crystal), Tape
    • Filters: 7 kHz steep‑cut (per channel), rumble filter (both channels)
    • Controls: Separate input selectors; concentric bass, treble and volume; ganged master volume with loudness compensation
    • Functions: Stereo, Reverse, Mono (L→both), Left only, Right only, Mix (both preamps→left amp)
    • Output stage: 2 × EL84 per channel, ultralinear push‑pull with global NFB
    • Valve complement: 2 × EF86, 6 × ECC83, 4 × EL84, 1 × 1CP1
    • Loudspeaker outputs: 16 Ω and 4 Ω, provision for damping resistor
    • Power supply: Metal rectifier, RC smoothing
    • Finish: Black chassis; dull‑gold panel and cover; gold‑anodised knobs

    Remarks
    Designed for maximum operational flexibility, offering facilities uncommon in contemporary stereo amplifiers, including oscilloscope‑based calibration and extensive channel‑routing options. Introduced at the 1959 Radio Show and positioned within the Emisonic product line following EMI’s takeover of S.T.D. marketing.

    A matching control‑unit version without the EL84 power stages was sold as the Stereoscope 556, offering the same dual‑channel preamplifier, filters, routing facilities and oscilloscope‑based calibration system for use with external power amplifiers.

  • Price in first year of sale
  • 66.15 £
  • Mentioned in
  • -- Original-techn. papers.
  • Literature/Schematics (1)
  • -- Original prospect or advert (The Gramophone Dec 1959, p.336, 367)

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