Pre-Amplifier Vari-Slope

A Mono Pre-Amplifier, to use with the Leak TL/10, TL/12 or TL/25 Power Amplifiers where a microphone input and a variable steep-cut filter are required.

Description.
Circuit: A low distortion two-stage feedback tone control pre-amplifier with microphone input facilities, drawing its LT/HT supplies from the main amplifier.
Input Selector: A five-position switch allows the following inputs:
  Microphone: Sensitivity, 4 mV. r.m.s. Input impedance 200kΩ.
  Tuner: Response, level. Sensitivity 60 mV. r.m.s.
  Records:
    The "78B" position is very accurately the inverse of the E.M.I.
      characteristic.
    The "78A" position is for American records, including LP's.
    The "LP" position is for Decca ("London" in the U.S.), the
      new E.M.I. 33⅓ and 45 records and for Columbia (U.S.) LP's.
  The pre-amplifier will operate from any pick-up generally available
    in the world. The sensitivity is 15 mV. at 1,000Hz for full
    power output from the associated TL/10, TL/12 or TL/25 amplifiers.
  Input impedance: 100kΩ.
Treble Control: A seven-position switch giving three positions of
  treble lift, +11dB at 10kHz, a level position and three positions of
  treble cut, the cut-off frequencies being 9kHz, 7kHz, 5kHz.
Slope Control: Continuously variable. Operative when the treble
  control is set at any of the cut positions. The variation in slope
  is from 50dB per octave to 5dB per octave.
Bass Control: A seven-position switch giving three positions of
  bass loss, -13dB at 40Hz, a level position and three positions
  of bass lift, +15dB at 40Hz.
Volume Control: The switch controls the power to the amplifier.
Spare Supplies: A socket marked "To Radio" is fitted from which
  the following supplies can be drawn:-
    Heater 6.3V. 1.3A A.C. H.T. 440V. 30 mA D.C.
Total Harmonic Distortion: Does not exceed 0.02%.
Dimensions: Front panel 10¾" x 3½". Chassis 10" x 3" x 2¾".

Price in 1955 £12 12s 0d plus purchase tax.

The Leak Vari-Slope II Pre-Amplifier additionally has tape facilities.

Here you find 43 models, 43 with images and 21 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from Leak, H.J.; London