Lafayette KT-600A
Lafayette's "Professional Stereo Control Center" promised laboratory-grade flexibility at a kit price, and the catalog copy backs up the swagger.
Overview
The KT-600A sits in an interesting spot in Lafayette's early-'60s lineup. It wasn't a tuner and it wasn't a power amplifier. It was a control center - a preamp in the fullest sense, the box that sat between your sources and your amplifier and did all the switching, balancing, and tone shaping. Lafayette marketed it as the "Criterion Professional Stereo Control Center." The kit-versus-wired price split shows who it was aimed at: the KT-600A in kit form at $79.50, or the factory-wired LA-600A at $134.50. That's a $55 gap in early-1960s money. Lafayette was betting plenty of hobbyists would solder their own signal path to save the difference.
The published response figure is 5 to 40,000 cps, ±1 db. That looks modest next to the KT-550 power amp's claimed 2 to 100,000 cps, but you have to read it in context. A control center's bandwidth claim is bounded by its tone-control and switching circuitry, and 40 kc was well past the audible range in an era when FM broadcast topped out around 15 kc. Sensitivity is listed at 2.2 mv for 1 volt out, which is a reasonable figure for the phono and high-level inputs of the period. The outputs are described as dual low-impedance "plate follower" types at 1500 ohms. That low output impedance means the KT-600A can drive long interconnects and a wide range of power amplifiers without the high-frequency rolloff that plagued some high-impedance preamp designs.
Distortion is quoted as less than .03% IM and less than .1% harmonic. Hum and noise is specified at 80 db below 2 volts. Lafayette printed those numbers in its catalog alongside the phrase "Precise 'Null' Balancing System," its term for a balance control that let the user zero the two channels against each other rather than eyeball a detented knob. The catalog also calls out a "Bridge Control" that provides a variable third-channel output, and a "Variable Cross Channel Signal Feed" that Lafayette claimed eliminates the "hole-in-the-middle" effect. That was a real problem in early stereo, where hard-panned recordings could leave a listener sitting in front of two disconnected speakers with nothing in between. There's also tape head playback equalization for 4-track stereo, which dates the unit to the era when open-reel tape was a serious source component and preamps were expected to handle the NAB curve themselves.
The KT-600A is listed at 14 x 10½ x 4½ inches, shipping weight 16 lbs. That's a substantial chassis for a preamp. The weight comes from the metal enclosure and the transformer and tube complement inside. Lafayette was explicit about the "Made in U.S.A." designation, which appeared prominently in the catalog listings next to the price. The unit was sold through Lafayette's retail locations in Jamaica and the Bronx, New York, Plainfield and Paramus, New Jersey, Newark, and Boston, as well as by mail order from the Jamaica address.
Period advertising placed the KT-600A in Lafayette's "Criterion" family, alongside the KT-550 100-watt basic stereo amplifier kit. Audio (April 1961, p.82) carried the KT-600A in its advertising index with the kit and wired prices, and Audio (January 1961, p.66) ran the same "Professional Stereo Control Center" listing with the response and balancing-system claims. High Fidelity (July 1962, p.6) featured the KT-600A as part of a complete Lafayette component stereo-phono system. That is how most of these units likely left the store, not as standalone preamps but as the control section of a matched system built around the LA-250A 50-watt stereo amplifier and a Garrard RC210 changer. It was designed to be the brain of a Lafayette-branded stack, and its switching and equalization were tailored to the sources Lafayette sold.
The catalog copy doesn't say how the KT-600A actually sounded or how it held up. The published specs are respectable for a kit preamp of the period, but they're manufacturer claims, not independent measurements. The "Null" balancing system and the bridge control are unusual features for the price class, and they suggest Lafayette was trying to set the KT-600A apart from the flood of generic preamps then on the market. Whether the execution matched the ambition, the surviving documentation doesn't say. The KT-600A was positioned as the top of Lafayette's preamp line at the time, with the LA-250A amplifier and KT-550 power amp as its natural partners.
For collectors today, the KT-600A is a niche piece. It's a kit-era tube preamp from a major American mail-order house, so it has a following among Lafayette completists and tube hobbyists, but it doesn't carry the cachet of the big-name separates. The kit version is the more interesting artifact. A factory-wired LA-600A is a nice piece of industrial design, but a KT-600A that someone actually assembled in 1961 carries the fingerprints of the hobby. The usual caveats apply: tube preamps of this vintage need recapping, the selenium rectifiers and carbon-composition resistors in the power supply are well past their service life, and any unit that's been sitting unused for decades should be brought up on a variac before it sees wall voltage. The 1500-ohm plate-follower outputs are low enough to be friendly to modern solid-state amplifiers, which makes the KT-600A more usable in a contemporary system than some high-impedance preamps of the same era. The tone controls and the bridge circuit are period pieces, not transparent additions to the signal path.
Documentation is thin. The KT-600A appears in Lafayette catalog listings and in the advertising pages of Audio and High Fidelity from 1961 and 1962, but no independent lab review of the unit has surfaced in the available material. The specs quoted here come from Lafayette's own catalog copy, so they should be treated as manufacturer claims rather than verified measurements. The 2.2 mv sensitivity, the 1500-ohm output impedance, and the distortion figures are all as-printed, and there's no way to know from the surviving sources whether a production unit met them.
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