McIntosh C-8 & C-8P mono preamplifier
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Taken from 'High Fidelity Magazine', April 1955

We are omitting specifications because we've published them before . . . and for once, we're going to illustrate only the backside of a piece of hi-fi equipment. The Mclntosh C-108 audio compensator and associated 30-watt amplifier were described in detail in our July 1954 issue. The C-8 has some added features; the "P" stands for the self-powered model.

The C-8 is intended for use with the MC-30 power amplifier, from which it normally takes its power and to which it is connected with a longish cable. When used without the MC-30, the small power unit provides the necessary voltages.

Specifications on the C-8 are essentially the same as those for the C-108, reported on previously. But—the C-108 was very flexible; the C-8 is more so! Its back- panel flexibility, hence the rear view in the illustration. Reading from left to right: at the top is the cable socket, for connection to the MC-30 power amplifier or the power supply (when used) for the C-8. Below are three AC outlets, controlled by the front panel switch. When the separate power supply is used, you get three more switched AC outlets! Next are two output jacks; both are cathode followers. The upper one is the main one, the lower one is for tape recorders and is not affected by tone, volume, or aural compensator (i.e., loudness contour) controls. To the right of the line cord is a switch that operates in conjunction with input channel 5. This channel is designed to operate from low-level magnetic cartridges and the knob to the right of the switch adjusts input load to match the requirements of different cartridges. That's when the switch is in the "MAG" position; in its other position, it adapts channel 5 for constant-amplitude cartridges such as crystals, ceramics, the Weathers, etc. Thus you have full equalization control over both magnetics and constant amplitude pickups. Channel 4 is for high level magnetics and, as delivered by the manufacturer, is terminated for Pickering units. Channels 1 and 2 are Standard high level inputs, for tuners, tape recorders, etc.; both have input level controls. Channel 3 is low level, high impedance, for microphones; it too has an input level control.
The input level controls are important. The C-8 is a very sensitive unit. That is, it delivers full output (2.5 volts to main jack, 1.0 volt to auxiliary or tape recorder jack) with very little input signal — only 70 millivolts on channels 1 and 2; 10 millivolts on the microphone channel (No. 3). Now most tuners and tape recorders, which you'd normally connect to channel 1 or 2, deliver 1 or more volts. That would overload the daylights out of the C-8 and make it distort badly if it weren't for the input level controls.

Well, we were enthusiastic about the C-108. We like this one better, because it is so completely flexible, fore and aft! 'Nuff said. —C. F.

MANUFACTURER'S COMMENT: The model MC-30 power amplifier is an improved version of the A-116 which was reviewed in the last TITH. Its outstanding change is the addition of a direct-coupled cathode follower driver which has reduced intermodulation distortion even at full output from ½ % to ¼ %. At the same time it is still possible to open-circuit or short-circuit the output terminals with full signal input at any frequency without damaging tubes or components. Since frayed speaker leads are often used in first tryouts, this feature keeps headaches to a minimum.