General Electric

  • BA-2-A. Program Amplifier. 1948. 6.7MB. Scanned and contributed by Tim Hughes.
  • BA-5A Limiting Amplifier. CBS designation 1-A Automatic Gain Adjusting Amplifier.

    • Source impedance: 600 or 150 ohms, balanced or unbalanced.
    • Input impedance: 600 or 150 ohms, approximately, balanced or unbalanced.
    • Load impedance: 600 ohms, unbalanced.
    • Output impedance: 600 ohms, approximately, if at least 6 dB attenuation is set up in adjustable output pad.
    • Input level:

      • Maximum (at verge of automatic gain-reduction): -2 dBm.
      • Maximum (with 12 dB gain reduction): +10 dBm.
      • Minimum (at verge of automatic gain reduction): -33 dBm.
      • Adjustable in 1 dB steps between above limits by means of panel mounted, 30-step, input level control.
    • Output level:

      • Normal (at verge of automatic gain reduction, and with zero loss in output pad) +12 dBm.
      • Adjustable in 0.2 dB steps by a panel-mounted 45 step, output level control.
      • Also adjustable in 1-dB steps to any value between +12 dBm and -28 dBm by means of soldered taps on output T pad.
    • Level indicator: A panel-mounted VU meter and associated multiplier attenuator may be switched across the output of either the control amplifier stages or the pre-amplifier stages, permitting monitoring of program levels, either before or after the point where gain-reduction takes place.
    • Frequency response: +- 1 dB 30Hz to 15kHz under any condition of gain reduction.
    • Gain: (with maximum input-level-control setting, zero loss in output pad, and normal setting of output level control): 44 dB.
    • Noise level: (below output signal level at verge of gain reduction): -70 dB, max.
    • Steady-state distortion: Less than 1% total rms distortion from 50Hz to 15kHz for all values of automatic gain reduction up to 12 dB.
    • Attack time: Less than 150 microseconds.
    • Recovery time: Automatic function of nature of program material.

      • For single, short peaks: 0.2 to 0.4 seconds, adjustable for 63% recovery of gain after signal drops below gain-reduction level.
      • For sustained or rapidly recurring peaks: Approximately the same as for single, short peaks up to about 40% gain-recovery, increasing automatically to about 7 seconds for 90% gain-recovery.
    • 6J7, 1621 preamp. Take-off point for control amp in anode of 1621. Delay network, balanced amp, 2 x 6J7, 2 x 1621 triode connected, 2 x 6J5 in feedback paths. Gain control amp, 6J5 phase splitter, 2 x 6Y6 cathode followers, 2 x 6X5 rects, 6SN7 DC amp, meter driver. Schematic (1.2MB) from The Radio Manual, Sterling & Munro, 4th edition, 1950. Contributed by Tim Hughes
  • BT-1-B 250 Watt FM Broadcast Transmitter - Phasitron based transmitter of 1949. Scanned by Dave Hershberger.

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