Amplifier 3 Watt Control Less

Mullard Wireless, London (see also Mullard Radio Valve)

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  • Year
  • 1956–1962 ?
  • Category
  • Kit (Parts plus instruction) or building instructions only
  • Radiomuseum.org ID
  • 367737

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

 Technical Specifications

  • Number of Tubes
  • 3
  • Main principle
  • Audio-Amplification
  • Wave bands
  • - without
  • Power type and voltage
  • Alternating Current supply (AC) / 50 Hz, 200 /220/ 240 Volt
  • Loudspeaker
  • - This model requires external speaker(s).
  • Power out
  • 3 W (max.)
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: Amplifier 3 Watt [Control Less] - Mullard Wireless, London see
  • Shape
  • Chassis only or for «building in»
  • Notes

  • This version of the Mullard Three‑Watt Amplifier is the control‑less variant published in Mullard – Circuits for Audio Amplifiers (1959). It uses the same EF86–EL84 signal path and the same EZ80‑based power supply as the standard version, but omits the volume and tone controls. Mullard intended this simplified version for use with a separate pre‑amplifier or with stereophonic equipment requiring matched channels.

    Circuit concept and performance
    Output power is approximately 3 W with an overall sensitivity of 100 mV. The EF86 is operated in a low‑current, reduced‑voltage mode to allow direct coupling to the EL84 grid. This provides high gain with minimal loading and supports around 20 dB of overall negative feedback.

    The feedback network is simplified compared with the standard version, as no tone‑control components are included. Frequency response remains essentially flat from 35 Hz to 30 kHz. Total harmonic distortion increases rapidly above about 3.5 W. Output impedance is under 1.5 Ω when used with a 15 Ω loudspeaker.

    Controls
    None.

    This version is intended to be driven from an external pre‑amplifier or control unit.

    Power supply
    Identical to the standard version: an EZ80 rectifier fed from a 300‑0‑300 V, 60 mA mains transformer, with a 50 + 50 µF reservoir/smoothing capacitor. A supply tap (C9) is provided for powering a companion pre‑amplifier.

    Construction and commercial use
    As with the standard version, this was a published design only. Mullard did not produce it as a commercial amplifier. It was widely used by hobbyists and by kit suppliers requiring a compact, economical power‑amplifier stage for mono or stereo systems. Recommended output‑transformer suppliers included Colne, Elden, Elstone, Gardners, Gilson, Hinchley, Parmeko, Partridge and Wynall.

    See also  the Standard version with volume, treble and bass controls.

  • Mentioned in
  • -- Original prospect or advert (Radio Constructor April 1956, p. 564-569, 579)
  • Literature/Schematics (1)
  • - - Manufacturers Literature (Mullard – Circuits for Audio Amplifiers, 2nd Edition, 1959. P.53-60)
  Mullard – Circuits for Audio Amplifiers, 2nd Edition, 1959. P.53-60 3744 KB
  • Documents regarding this model
  • Author
  • Model page created by Gary Cowans. See "Data change" for further contributors.

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