Heathkit EA-3 (1960)

The Heathkit EA-3 was a stereo preamplifier/control unit introduced in 1960. It was the entry-level tube preamp in Heathkit's lineup, the companion control unit to the AA-15 (20W) and AA-21 (28W) stereo power amplifiers. It completed Heathkit's first fully modular stereo "separates" system, built on the "Electronic Workshop" concept of interlocking, powered modules. It sat below the higher-spec SP-2 and was aimed at kit builders new to high fidelity.

The EA-3 has no internal power transformer. It drew its power from the mating Heathkit power amplifier through a 6-pin Jones plug connector cable. Heaters ran on 12.6V DC from the amplifier's filament supply, which cut hum. The phono stage used two 12AX7s (one per channel) with a passive RIAA network between the first and second triode sections, plus a small feedback loop. The line stage used two 12AU7s, direct-coupled plate-to-grid between stages. All tube sockets were ceramic. Controls were a source selector (Phono/Tape/Tuner/Aux), balance, volume, and a Loudness contour switch.

Specs from the assembly manual: frequency response 20 Hz-20 kHz ±1 dB, RIAA accuracy within ±0.5 dB, maximum output 2.5V RMS, channel separation 50 dB at 1 kHz, S/N 60 dB below rated output (phono), phono sensitivity 4 mV, phono input impedance 47 kΩ, phono stage gain 40 dB at 1 kHz. Dimensions were 12-1/2" W × 3-1/2" H × 8" D, weight 6 lb.

Heathkit rated the kit difficulty "E" (Easy), with assembly time of 3-4 evenings. The 1960 U.S. kit price was $29.95, and no factory-wired version was listed. High Fidelity (December 1959, p.38) described it as a successor to the famous EA-2, delivering a full 14 watts of hi-fi rated power and easily meeting professional standards as a 12-watt amplifier - a budget-priced preamp/amp unit.

Owner reports over the years have been mostly positive. The phono stage is "surprisingly open" and the de-emphasis network was done right. The loudness contour is widely considered too aggressive, and the source switch is flimsy. The original Aerovox electrolytic capacitors are almost universally drifted or leaking by now, so recap before powering up. The 6-pin Jones plug is frequently cracked or corroded, and replacement plugs in this pin configuration are no longer manufactured. Restored EA-3s paired with a matching AA-21 have been reported selling for $300-$400 as a pair. Bare units in non-working condition go for $40-$75. The full original assembly manual is available as a free PDF via WorldRadioHistory.