SUPREME 700C preamplifier

Total Control Flexibility
Many of the design parameters of a truly professional preamplifier-control posed a difficult challenge to Kenwood's engineers. On the one hand, a high quality control unit must afford total flexibility, input and output facilities, and convenient control of a variety of program sources. At the same time, the output signal must be totally free of distortion - an exact replica of the input signal. The 700C is the result of over two years of research and development. It is intended to serve as the control center of any high quality stereophonic component system. Its deceptively simple control layout may obscure its many control innovations, but there is virtually no limit to the variety of control and switching functions which can be performed with this exceptional component.

Precise, Resettable Volume and Tonal Compensation
Consider the massive, centrally located master volume control. It operates in two dB steps rather than continuously, enabling you to reference desired levels for future use at any time. Individual bass and treble controls for each channel are also adjustable in 2dB increments, for precise, repeatable tonal compensation. Selectable cross-over frequencies of 200Hz and 400Hz for the bass control and 3kHz and 6kHz for the treble control permit tonal compensation of just that portion of the audible spectrum that requires adjustment, and when the selector is moved to the off position, tone control circuits are totally bypassed insuring absolutely uniform response ("0dB tolerance") from 20Hz to 20kHz.

Selectable Loudness and Filtering Controls
Other controls include two-step (-10dB and -20dB) audio muting and a two-step loudness control circuit so that proper level relationships can be established between input signal level and preferred Fletcher-Munson compensation contours. Selectable low-frequency filtering with cut-off frequencies of 40Hz and 20Hz (subsonic) is provided at an attenuation rate of 18dB per octave. High frequency filtering at 6kHz and 12kHz effectively attenuates surface noise and other high frequency noise components from program sources without materially affecting tonal response.

Special Front Panel Jacks
Stereo microphone inputs are front-panel accessible, as is stereo headphone jack driven by its own independent headphone audio amplifier.

Selectable Phono Impedance
Selectable phono cartridge input impedance (with settings for 600Ohm, 30kOhm and 50kOhm) is another refinement included in the circuitry of the 700C. Equalization is precisely designed to follow the entire RIAA internationally accepted recording curve within ±0,2dB.

Dynamic Range and Linearity
The term dynamic range has been applied to just about every high fidelity component from the stereo cartridge to the loudspeaker system. Unless the intervening electronics of a component system is capable of amplifying and reproducing the inherent dynamic range of the program source, that quality in reproduced music can easily be degraded. All signals, regardless of their relative amplitudes, must be reproduced with a minimum of noise and with a faithful linearity. The inherently low residual noise of the 700C (less than 50µV) means that this unit is capable of handling a dynamic range in excess of 85dB, referred to its nominal 1V output level - a figure far in excess of any currently available musical program source!

Unique Switching Circuitry for Optimum Convenience
For all its versatility, the 700Cs simplicity of operation attests to the care and layout. Consider, for example, the use of lever and rotary selector switch, acting together to permit selection of most often used program sources. No need to traverse all function switch settings to turn the tuner on. Or the MODE switch which permits every conceivable combination of single channel or dual channel reproduction of input signals through the two stereo speaker systems. There are two complete tape monitoring circuits, too, with a special "tape-through" circuit which permits you to record from one deck to another while listening to a different program source at the same time.

Nice and detailed "nudies" of an EW-restored 700C can be seen here.