Scott LC-21
A kit preamp that promised laboratory-grade quiet, and by the accounts of the day, delivered it.
Overview
The LC-21 was H. H. Scott's stereo control center in kit form. The company pitched it as clean enough for lab work, not just home listening. Scott's own catalog copy claimed distortion "below the limits of even the finest test equipment" and hum that was "completely inaudible even in the magnetic positions." There was real engineering behind the hum claim: an all-aluminum chassis, a shielded power supply, and d.c.-heated tubes on the filaments. Owners who've lived with one will tell you the d.c. heater design is the reason the phono stage is so quiet.
The feature set was generous for a kit. Scott listed sixteen front-panel controls, including full tape-monitor switching, a front-panel "derived" center-channel level control, and a phase-reverse switch. The catalog also noted the LC-21 could be pushed below 10 cps for laboratory applications. It was built as a companion to the LK-150 stereo power amplifier, and Scott's literature pairs the two repeatedly.
The published specs: frequency response of 10 to 55 cps ±1.0 dB at 2.5 volts, harmonic distortion of 0.1% at 2.5 volts, and hum and noise 85 dB below 1 volt. Phono sensitivity was rated at 0.3 mV for rated output, tuner at 0.5 volts. The tube complement ran six 12AX7s plus a single 6X1. Weight was 13 lbs, and the chassis measured 15½ inches wide, 5½ high, and 13½ deep. The kit listed at $99.95, with accessory cases in various woods and metal starting at $15.95.
High Fidelity (February 1963, p.59) walked through the LC-21's control layout in detail, noting dual concentric bass and treble controls for each channel, concentric stereo balance and center-channel level controls, and a loudness control that incorporated a push-pull AC power switch. The same review described the slide switches above the knobs — pickup selector for high or low impedance magnetic input, tape monitor, rumble filter, scratch filter, phase reversal, and loudness contour — and called out two high-gain inputs per channel, one at 47K-ohm input impedance (magnetic I) and another at 150K. That's the kind of granular period description that tells you the review actually sat with the unit.
Contemporary reception was warm. American Record Guide (April 1962), quoted in Scott's own advertising, reported that noise was "totally inaudible under any listening conditions" and that listening with the LC-21 was as rewarding as with the power amplifier. It appeared in a Scott ad, so allow for that. The same notice praised the kit build itself, estimating about a week's worth of evening work to assemble a "superb electronic control center." Scott's full-color instruction books were a selling point in their own right.
The LC-21 sits in a slightly awkward spot in the collector world. One period service column (1995) called it "a very nice unit" but cautioned that LC-21s aren't common enough to be casual hack-up candidates, unlike the plentiful Scott integrated amps. Scott power amps, the same writer noted, are genuinely hard to find. That cuts both ways: the LC-21 is a period-correct match for an LK-150, but parts and spares aren't lying around in quantity. Buyers should expect to pay for a clean one, and should look closely at the d.c. heater supply and the switchgear, which carry the most wear on any preamp of this age.
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