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
  • DC-35 Audio Console

  • BT-1-B 250 Watt FM Broadcast Transmitter - Phasitron based transmitter of 1949. Scanned by Dave Hershberger.

*Phasitron - Dave Hershberger's page on the GE Phasitron. See also patent 2,461,250 by Francis M. Bailey on the Electric Discharge Device and System, February 8, 1949, assigned to General Electric. *GE Quadraphonic - Jim Tonne has contributed photos and history of the development of quadraphonic transmission equipment for General Electric by Moseley Associates. *GE TRANSMITTER EQUIPMENT - During the late 1940's and early 1950's much of television engineering was in what may be termed the 'experimental' stage. Most VHF transmitters were limited to about 5 KW peak visual power and about half that power for the aural. The General Electric Company built one of the first really 'large' high band amplifers that would take the 5 KW of an early RCA, Federal or GE TT-6 and bring it up to a full 50 KW peak visual and 26.5 KW FM for the aural. This amplifier was very popular and this basic design was in use until GE retired from the transmitter field in the late 1960's. Only the tubes and a number of parts were updated. The TT-35 series (of which this amplifier with a TT-6 driver would make) stayed in the field for many years. Notable stations used the TT-35 package. WHAS-TV and KSL-TV are but two of those notable stations. Manual contributed by Alan Kline and scanned and notes by Stanley Adams.

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