10-10

Mullard Wireless, London (see also Mullard Radio Valve)

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  • Year
  • 1961 ?
  • Category
  • Kit (Parts plus instruction) or building instructions only
  • Radiomuseum.org ID
  • 367383

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

 Technical Specifications

  • Number of Tubes
  • 7
  • Main principle
  • Audio-Amplification
  • Wave bands
  • - without
  • Power type and voltage
  • Alternating Current supply (AC) / 200 / 220 / 240 Volt
  • Loudspeaker
  • - This model requires external speaker(s).
  • Power out
  • 20 W (max.)
  • Material
  • Metal case
  • from Radiomuseum.org
  • Model: 10-10 - Mullard Wireless, London see
  • Shape
  • Chassis only or for «building in»
  • Notes

  • The Mullard 10‑10 is a 10‑watt stereophonic valve amplifier design published by Mullard as part of their application‑note series promoting the use of Mullard valves. It is a high‑quality stereo amplifier using EF86 low‑noise pentodes for the input stages and ECL86 triode‑pentode valves in a long‑tailed‑pair phase splitter and push‑pull output configuration. Mullard presented the design in several constructional articles and booklets, offering full circuit data, performance graphs, and recommended transformer specifications.

    The amplifier provides passive tone‑control networks, balance control, and a shared power supply using a GZ34 rectifier. Mullard published both wired and printed‑circuit versions, with detailed layout guidance to minimise hum, stray capacitance, and instability.

    Technical Data

    • Output power: 10 W per channel (class AB, distributed loading)
    • Output transformer: 9 kΩ anode‑to‑anode load, 20% UL taps, 100 H primary inductance (typical Mullard spec)
    • Sensitivity: 23 mV with feedback; 210 mV including tone controls
    • Frequency response: approx. 12 Hz – 35 kHz (±3 dB at 10 W)
    • THD: typically, 0.15% at 10 W
    • Output impedance: approx. 1.4 Ω at 1 kHz (damping factor ~10.7)
    • Tone controls: passive bass/treble, ±12 dB
    • Power supply: 6.3 V heater supply (3.2 A for ECL86 + EF86), HT approx. 315 V at full load

    Circuit Notes

    • Input stage gain approx. ×120 using EF86.
    • Phase splitter uses the triode sections of the ECL86 in a long‑tailed pair with fixed bias.
    • Push‑pull pentode output stage delivers 10 W
    • Overall negative feedback approx. 20 dB, with phase‑advance network for HF stability.
    • Mullard emphasised careful wiring, grounding, and screening to prevent oscillation due to the high gain of the ECL86.

    This amplifier was not manufactured or sold by Mullard. The 10‑10 was issued purely as a constructional project to demonstrate the performance of Mullard valves and to encourage their adoption by hobbyists, kit suppliers, and manufacturers. Mullard supplied the design, data, and recommended components, but never marketed a kit or finished amplifier.

    Commercial kits and chassis based on the Mullard 10‑10 were sold by independent suppliers, including Sterns and other radio/hi‑fi retailers around the world. These third‑party kits followed the Mullard design but were not Mullard products.

  • Mentioned in
  • - - Manufacturers Literature (Ten-Watt High Quality Stereophonic Amplifier)
  • Literature/Schematics (1)
  • - - Manufacturers Literature (Ten-Watt High Quality Stereophonic Amplifier)
  • Author
  • Model page created by Gary Cowans. See "Data change" for further contributors.

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