the ALTEC A-440A

preamplifier

The A-440A is an integrated switching, amplifying and equalizing unit designed to the exacting standards when professional use is making no compromise with style. Simplicity of operation is provided, for when the controls are set and the panel is potted, the unit is fully necessary to use the single visible control. There are three high level and two low level inputs with separate level controls. The low level inputs have nearly fifty times the frequency of equalization for proper preamp characteristics as well as high frequency and medium signals. High level inputs accommodate radio and television tuners and equalized output tape. Bass and treble tone controls extend the user's control. A loudness control shapes the frequency response of the riproduct of the normal condition of equal loudness. A switch provides standard operation.

Two outputs are provided, the first to the power amplifier and the second for connection to a magnetic tape recorder. Output to the tape is unaffected by adjustment of the tape. A feedback switch, switching circuit allows use of input facilities and magnetic equalization circuits for tape recording while monitoring from the tape playback head. This switch separates the functions of the preamplifier so that the tape output signal is sent into the preamplifier at the volume control leaving the equalizer and input facilities connected to the recorder output jack.

The equalizer phase section consists of a two-stage amplifier with R.C. networks as a feedback loop to provide the required characteristics. Several advantages reset from this equalization method negative feedback is active throughout the usable transmission range, reducing distortion resulting from uneven tube performance. Most important, passive four-terminal R.C. networks providing standard playback circuit, when extended to the 30 or 40 cycle region, reach their asymptotic transmission characteristics in the 6 to 70 cycles range. This large transmission at low frequency corrects the addition of a supplemental sharp cutoff filter to turnable runout is to be reduced to unobservable levels. With feedback equalization switch cutoff below a critical frequency may be obtained. See Figures 2-7.

Following the volume control is a flat twist-amplifier with negative feedback. This produces reasonably large output voltages at low distortion and provides a comparative low distortion point impedance for the tone controls.

Selection between two gain inputs is achieved by means of a selector switch. Low frequency cross-over and high frequency radio/ controls both provide flat positions, allowing the use of high impedance level controls through the piano-channel without circuit modifications.

Microphones are provided for each input jack, allowing the inputs to be in proper balance and appropriate level for suitable operation of the loudness control.

SPECIFICATIONS

Input Range: 100 Hz to 1000 Hz.

Output Range: 100 Hz to 1000 Hz.

Maximum input amplitude: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum output amplitude: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum input frequency: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum output frequency: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum input voltage: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum output voltage: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum input current: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum output current: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum input power: 1000 Hz, 1000 Hz to 10000 Hz.

Maximum output power: 1000 Hz, 1000 Hz to 10000 Hz.

Frequency Response

See Tables 1-7.

Note: All values are in dB. All ratios are relative to 100 Hz.

Controls

Volume: Select mode for three levels.

Pan: Select mode for three levels.

Tune: Select mode for three levels.

Tune/Volume: Select mode for three levels.

Tune/Pan: Select mode for three levels.

Tune/Volume/Pan: Select mode for three levels.

Tune/Volume/Pan/Select: Select mode for three levels.

Pan/Volume: Select mode for three levels.

Pan/Volume/Select: Select mode for three levels.

Pan/Volume/Pan: Select mode for three levels.

Pan/Volume/Pan/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select/Select/Select/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select/Select/Select/Select/Select/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select: Select mode for three levels.

Pan/Volume/Pan/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select/Select: Select mode for three levels.