Heathkit AP-1800 (Late 1970s)

Name: Heathkit AP-1800
Brand: Heathkit

The Heathkit AP-1800 is a solid-state stereo preamplifier from the late 1970s, sold in kit form for $299.95. It was the matching companion to Heathkit's AA-1800 power amplifier, and at least one period reviewer called the pairing "one of the finest preamp/amp combinations Heathkit ever produced." The AP-1800 replaced the earlier AP-1615 in the Heathkit line.

The AP-1800 is built around a two-stage RIAA phono equalization circuit, a discrete output stage buffer, and an unregulated supply for the output stages. The front panel uses push-push switches for source selection and was designed for optional rack mounting. The spec sheet is respectable for the era. Frequency response runs from 5 Hz to 100 kHz, total harmonic distortion is under 0.002%, phono signal-to-noise is above 80 dB, and high-level S/N is above 95 dB. Phono input sensitivity is rated at 2 mV with 100 mV overload, and high-level sensitivity is 150 mV. Tone controls give ±10 dB at 100 Hz and 10 kHz. Inputs are phono, tuner, aux, and two tape loops, with dual tape outputs and a pre-out. The unit measures 19"W x 3.5"H x 9"D and weighs 11 lbs.

Surviving documentation on the AP-1800 is thin. HI-Fi-Stereo-Buyers (May 1980, p.56) listed it at $379 in kit form, with a full range of control functions suitable for the average audiophile's system requirements. It also noted a three-level phono input sensitivity selector and an LED phono overdrive indicator - features the basic spec sheet doesn't cover. The two sources disagree on price, and nobody has settled it. The $299.95 figure comes from the product's own documentation, while the magazine listing may reflect a later price.

Collectors today describe the AP-1800 as a rare unit that "barely surfaces" on the used market. One forum user who upgraded his unit with Cardas wiring called it "highly-regarded." Exact production years are not documented, and no current market valuations have been recorded.