Electro-Voice EVR-4X4
A four-channel AM/FM receiver with a single decoder circuit meant to end the matrix-format wars. No switching, no guessing, no picking sides.
Overview
Four-channel sound in the early Seventies was a mess of competing matrix schemes. Electro-Voice's answer was to stop asking listeners to choose. The EVR-4X4 receiver carried the company's Universal Decoder circuit built right in, and according to Electro-Voice's own advertising the set would "properly decode any matrix 4-channel input without switching." That was the pitch: a receiver that handled SQ, Stereo-4, and the rest of the matrixed formats without the owner flipping a mode switch or picking a camp. HiFI-Stereo (September 1972, p.118) ran the claim prominently, calling the built-in circuit "the world's first universal four-channel decoder."
The hardware behind that claim was substantial. Electro-Voice billed the receiver as four complete amplifier channels plus multiplex stereo FM with a ceramic IF filter and integrated-circuit AM. That is a full four-channel front end, not a stereo receiver with a decoder bolted on. Most "quad" gear of the period was still a decoder in a small box, so this was a serious piece of furniture by comparison. The Universal Decoder itself was covered under U.S. Patent No. 3,632,886, which Electro-Voice cited in its literature as the basis for the circuit.
Electro-Voice sold the decoder two ways. Buyers who already owned stereo gear could add the standalone EVX-44 Universal Decoder for $99.95. Buyers starting from scratch could take the EVR-4X4 receiver at $249.95 and get the decoder built in. The company framed this as a choice rather than a hierarchy. The original EVX-4 remained the budget option for matrix decoding and stereo enhancement, while the EVX-44 and the EVR-4X4 carried the newer, more accurate universal circuit. HiFI-Stereo (October 1972, p.142) listed both prices side by side in the same spread, so the receiver's premium over the standalone decoder is easy to see.
The design also anticipated that "discrete" four-channel sources might take hold. Electro-Voice designed both the receiver and the decoder to accommodate discrete inputs such as 8-track tape. That was a hedge, not a commitment, since the company was publicly betting on matrix four-channel while leaving the door open. Per the period literature, the receiver could not decode discrete formats on its own. The discrete path was an input provision, not a demodulator. Owners who wanted true discrete playback still needed outboard gear.
The separation enhancement is where the EVR-4X4's decoder differs most from a plain matrix decoder. Electro-Voice described a circuit that automatically increased center-front-to-back isolation to as much as 18 dB, at the cost of some left-right separation, and acted only when a center soloist was performing. The enhancement could be switched on continuously or off completely, and it worked across all encodings as well as plain two-channel stereo records. HiFI-Stereo (December 1972, p.150) described the receiver as decoding any matrix FM, record, or tape source "just as the record producer intended," which reads better in a brochure than in a listening room. The underlying circuit was real and patented, though, and the switchable enhancement let owners dial it back when the effect got heavy.
Reception in the period press was warm but not uncritical. HiFI-Stereo (September 1972, p.118) gave the receiver a full feature rundown and treated the universal decoder as the headline. DB-Magazine (November 1972, p.42) ran the same "world's first universal four-channel decoder" line in a spread that spent most of its column inches on speaker aesthetics rather than the receiver itself. Electro-Voice's marketing did the heavy lifting here. The receiver was positioned as the answer to format confusion, and the press repeated the framing. Independent measurement of the amplifier sections is not documented in the available material, so claims about power output and distortion should be treated as manufacturer figures rather than verified numbers.
For collectors, the EVR-4X4 is a period piece with a specific appeal. It is one of the few receivers that can play back a stack of mismatched matrixed quad records without the owner sorting them by encoding scheme, which a single-format decoder cannot do. The trade-off is that the receiver's value is tied to the matrix era. Owners who want discrete four-channel, or who mainly listen to two-channel stereo, will find the feature set less compelling, and the 18 dB separation enhancement is a coloration some listeners will leave switched off. Buyers should confirm the decoder works across multiple matrix formats before committing, since that circuit is the reason to own the receiver at all.
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