Documentation on the Heathkit KIT-70 is thin. The Archive has turned up exactly one period review that plausibly covers it. Audiocraft (September 1957, p.4) ran a column by Joseph Marshall on the "Heathkit 70-Watt Amplifier Kit." The model number strongly suggests this is the unit, though the review never uses the KIT-70 designation. Marshall cited a claimed frequency response of 10 to 40,000 cps, or within 6 dB from 2 to 200,000 cps, and called the distortion curves especially complete. His larger point was that the hi-fi industry needed detailed performance verification. He felt the kit's published figures were impressive, but the information needed to confirm them in practice was lacking.
That is essentially the whole surviving record. No Heathkit catalog pages, manuals, pricing, production dates, or confirmed surviving examples have surfaced. The Archive's file also contains a page from Audio (August 1964, p.33) describing a Heathkit amplifier with 15 watts per channel, preassembled etched circuit boards, and a three-hour build time. That reads like an ad for a smaller, later Heathkit model that got mixed into the file, so its specs shouldn't be attributed to the KIT-70.
Type: amplifier kit
Claimed frequency response: 10-40,000 cps; within 6 dB, 2-200,000 cps
Period source: Audiocraft, September 1957
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