Lafayette KT-900
A 25-pound transistor integrated amplifier that promised 60 watts per channel for $134.50. By one kit report's own curves, it delivered its cleanest power only after you'd pushed it well past idle.
Overview
The KT-900 is a Lafayette integrated stereo amplifier built around transistors, at a time when the industry was still arguing about whether solid-state belonged in serious hi-fi. It weighed 25 lbs and cost $134.50 from Lafayette Radio. That put a 60-watt-per-channel transistor integrated within reach of a kit-minded hobbyist. The "printed terminal board construction" dates it precisely. It is built on circuit boards with terminal strips, the kind of amp a careful owner could service with a soldering iron and a schematic.
The feature set is unusually complete for the money. There are individual concentric bass, treble, and volume controls - the clutch-type dual-concentric arrangement that lets one knob trim both channels together. A mode selector offers right channel, left channel, stereo, and reverse. Rumble and scratch filters are on board. The inputs are generous: two phono, two tape head, two auxiliary, and two tuner. Output taps cover 4, 8, and 16 ohms. That is a lot of switching and a lot of inputs for a mid-line integrated, and it reflects the era's assumption that an amplifier sat at the center of a system with a turntable, a tape deck, and a tuner all plugged in at once.
The published specifications are where the KT-900 gets interesting. Lafayette rated frequency response at 5 to 25,000 cps ±1 db at 60 watts output. Separately, it claimed harmonic distortion of 0.5% at 35 watts across that same 5-to-25,000-cps band. Put those two numbers together and the 60-watt figure is the HIF music-power rating, while the 0.5% distortion spec is tied to 35 watts. IM distortion was quoted at 1%, hum and noise at 75 db below rated output, and sensitivity at 10,000 microvolts (10 mV). The frequency-response and distortion claims are anchored to different power levels. That was common practice for the period, but it makes the KT-900's "60 watts" a music-power number rather than a continuous one.
The independent bench work tells a more complicated story. In a kit report on four transistor amplifiers, Electronics Illustrated published distortion curves for the KT-900's two channels driving 8-ohm loads. It observed that IM distortion was high at low power levels but dropped as power increased. That is the opposite of what most listeners expect, and a real characteristic of early transistor designs running class-B-ish output stages. The same report's frequency and power-response curves, taken at 5- and 30-watt levels, found the bass and treble boost and cut "rather fast." They put the rumble filter's 3-db-down point between 150 and 200 cps, depending on where the volume control sat. The bass-cut action, 15 db of cut between 35 and 46 cps, was likewise volume-dependent. So the filters and tone controls don't behave as fixed networks, and the controls interact rather than act independently.
A caution for anyone chasing the original review: Electronics Illustrated later ran a correction stating that the curves for the Lafayette KT-900 and the Realistic 208 had been interchanged in the original November installment. It reprinted them in correct position in the January 1964 issue. Anyone citing the first printing's curves is citing the wrong amplifier. The corrected curves confirm the low-power IM-distortion behavior described above.
The catalog pages of the period show where the KT-900 sat in the Lafayette line. It was the larger sibling to the KT-250AWX (a 50-watt integrated at $74.50) and the KT-236AWX (36 watts at $59.50). At $134.50 it was roughly double the price of the KT-250AWX and offered more power, more inputs, and the concentric control layout. It was not Lafayette's flagship, since the catalog also listed a KT-900WX variant. It was the model a buyer stepped up to when the smaller integrateds ran out of headroom.
The KT-900 is not a quiet, refined modern amplifier. The high IM distortion at low levels is the honest flaw here. The amp is at its least linear when you're listening softly, which is when grit is easiest to notice. The volume-dependent filter behavior is a second quirk, and it will frustrate anyone expecting predictable tone shaping. Against that, the build is serviceable, the input count is generous, and the price bought real power for the money.
Original documentation for the KT-900 is thin, and the model does not appear in the usual places collectors look first. Anyone considering one should verify the specific variant (the KT-900WX designation appears in period catalog listings). They should also inspect the printed terminal boards for the cold joints and aged capacitors that 1960s transistor gear accumulates. The 25-lb weight and the 13⅜-inch-wide, 4-inch-high, 12⅝-inch-deep chassis make it a compact, shelf-friendly unit.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.