The remaining four sections have several functions. There are equalizer-amplifier stages: high-gain circuits designed to bring up the level of such devices as magnetic phonograph cartridges and at the same time to impose the proper playback characteristic on the frequency response. There is one of these stages for left and another for the right stereophonic channels. THe remaining two sections consist of the two amplifying-tone control stages, one for left and one for right channel. High level signals such as those from a radio tuner are fed through these stages, and the functions of volume control, tone control, and similar control functions are accomplished at these points in the circuit.
Inputs: 3 stereo low level: RIAA phono, NAB tape head (7-1/2"), "Special" (optional second phono, microphone, etc.). 4 stereo high level: FM-AM, FM-Multiplex, Spare, Tape.
Outputs: Tape output. Audio output.
Controls: Selector, Volume, Balance, Blend, Individual Treble and Bass for each channel, Tape Monitor, Loudness, Scratch Filter, Power.
Tone Control Range: ±14 dB at 20,000 cycles; ±20 dB at 20 cycles.
Distortion: Less than 0.05% intermodulation at 2 volts (sufficient output to drive any amplifier). Distortion does not increase at low settings of volume control. Harmonic distortion below the measurement capabilities of regular commercial grade test equipment.
Response: ±.5 dB 10 cps to 40 kc. Response not affected by position of volume control.
Transient Performance: Passes square waves without ringing and with minimum deformation from 20 cps to 20,000 cps. No overshoot or bounce on pulse type signals. Instantaneous recovery from overload.
Hum and Noise: 2 microvolt equivalent noise input on RIAA. 74 dB below level of 10 millivolt signal.
Output impedance 1,000 ohms. Terminating impedance 100,000 ohms or higher. Low level input impedance 50,000 ohms; high level input impedance 250,000 ohms.