Heathkit AA-2004 (1972)
Heath's four-channel answer to a format war nobody won. 200 watts, discrete or matrixed, in a kit you soldered yourself.
Overview
Two hundred watts across four channels, a built-in matrix decoder, and a price of $349.95 in kit form. That was Heath's pitch for the AA-2004, and in 1972 it was a serious one. The AA-2004 was an integrated amplifier built for the four-channel moment, when discrete and matrixed quadraphonic were both fighting for the buyer's ear and nobody could say which would survive. Heath refused to choose. The AA-2004 handles mono, stereo, matrixed four-channel, and discrete four-channel, and it does so without obsoleting the stereo gear already sitting in the living room.
The power numbers shift depending on where you look. Heath's own literature is inconsistent across placements. One version of the spec lists 260 watts into 4 ohms (4x65), 200 watts into 8 ohms (4x50), and 120 watts into 16 ohms (4x30). A later placement describes the same amplifier as producing 500 watts into 4 ohms (4x50), 200 watts into 8 ohms (4x50), and 120 watts into 16 ohms (4x30). The 8-ohm and 16-ohm figures are stable across both. The 4-ohm rating is the one that wanders. The architecture is consistent: four conservatively rated, fully protected amplifier sections, controlled in pairs. One complete stereo system drives the left and right front speakers and another drives the left and right rear. That means the AA-2004 can be used as two separate stereo systems, or, with both main and remote speaker outputs, as two complete four-channel systems driving up to eight speakers. High Fidelity (May 1972, p.23) ran the AA-2004 alongside Heath's other new four-channel and digital offerings, framing the kit line as a way for the individual hobbyist to stay hands-on as hi-fi grew more sophisticated.
The measured performance is respectable for the period and the price. Power bandwidth on all channels runs from below 5 Hz to beyond 45 kHz. That figure looks extravagant until you remember it's the window in which the amplifier holds its distortion spec, not a claim about what you can hear. IM distortion is under 0.2%, damping factor is greater than 100, and hum and noise sit at -65 dB for phono and -75 dB for tape and aux. Those are clean numbers for a four-channel integrated of the era. The damping factor in particular suggests the amplifier has real grip on speaker loads.
The control set is the draw for the four-channel curious. Duplicate controls are provided for front and rear bass, treble, balance, and volume, with phono, tuner, aux, tape, and tape-monitor inputs. Mode switches select mono, stereo, matrixed four-channel, or discrete four-channel. Twenty input-level adjustments, enough for five separate four-channel sources, are reachable from the bottom of the chassis. That means flipping the thing over more often than you'd like. Separate rear-panel jacks give direct access to preamp outputs and power-amp inputs, permitting biamplification by simply adding a crossover network. Four calibrated VU meters with a meter-range switch for three power levels round out the front panel, a detail noted in contemporary coverage of the model.
Building one is part of the appeal, and Heath leaned into it. Plug-in circuit boards and preassembled wiring harnesses cut down on point-to-point wiring, which makes the AA-2004 as much fun to assemble as it is to use. That claim reads as marketing until you've spent an evening with a bag of resistors and a soldering iron. The kit shipped at 39 lbs. less cabinet. The preassembled, prefinished pecan cabinet (AAA-2004-1, 7 lbs.) was available separately at $24.95. A bare Heathkit chassis is a working object, not a living-room object, and the pecan enclosure is what turns it into furniture.
What the AA-2004 is not is a survivor of a winning format. Four-channel sound in its discrete and matrixed forms never consolidated the way stereo had, and an amplifier built around a format war is only as useful as the software that fed it. That's the honest knock on the AA-2004 as a collector's piece: its four-channel modes are period curiosities now, and the matrix decoder's "hidden presence" trick is a solution to a problem most listeners no longer have. But the underlying amplifier — four protected channels, wide bandwidth, high damping factor, biamp-ready preamp/power-amp separation — remains a capable and unusual piece of Heath engineering, and the kit-build provenance gives it a place in any collection of the company's more ambitious 1970s projects.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.