Lexicon LXP-1 (1988)

A half-rack reverb that runs on a 9-volt AC wall wart and weighs three and a half pounds, with a real Lexicon algorithm inside.

Overview

The LXP-1 is small enough to disappear in a rack bag. At 3.5 lb (1.59 kg) it is light enough that you forget it's in the chain until you bypass it. The chassis measures 8 inches wide, 1.7 inches high, and 8 inches deep. That makes it a half-rack box that slides onto a shelf or sits on top of a keyboard without complaint. It runs on an external 9 VAC, 1 A transformer, the wall-pack kind that shows up in a drawer years later with no label on it. It is not a studio rack fixture in the PCM sense. It's a processor built to travel.

Inside is more serious than the exterior suggests. The service manual lays out a power supply with three regulated rails: +5 VDC, +12 VDC, and −12 VDC. The ±12 volt supplies are built from voltage-doubler rectifier circuits that stack the stored charge of one AC half-cycle onto the next. That gets roughly ±20 to ±22 VDC unregulated before the TO220 regulators (7805, 7812, 7912) clean it up. The +5 V rail comes off a single half-wave rectifier and two 1000 µF capacitors. It feeds the reset and battery backup circuitry that manages non-volatile memory across power cycles. There's a 0.01 µF cap across the AC input, plus ferrite beads with filter capacitors to keep circuit-generated RF off the power line.

The reset behavior is documented down to the volt. A voltage divider monitors the unregulated +5 V rail. When the AC line sags into the 88-100 VAC range, the reset circuit trips the processor, and a normal 100-120 VAC input holds it above threshold. The service procedure says the transformer should put out 9.3-9.9 VAC across C22 with 117 VAC at the wall. The regulated rails should sit at 4.75-5.25 VDC, 11.40-12.60 VDC, and −11.40 to −12.60 VDC, with under 1 mVAC of 60 Hz ripple. If a unit is dead, that's where the trail starts.

Frequency response is quoted at 20 Hz - 15 kHz, ±1.0 dB for the wet signal, and 20 Hz - 20 kHz, ±0.5 dB dry. The wet path rolls off at 15 kHz because this is a reverb processor, not a full-bandwidth signal path. Dynamic range is 85 dB typical. THD is under 0.07% at 1 kHz wet and under 0.05% dry. Input impedance is 50 kilohm in stereo and 25 kilohm in mono, and the manual notes the single-ended inputs accept levels from −20 to +15 dBV. Output impedance is 600 ohms. Minimum input signal is −20 dB. None of those numbers will frighten a modern interface, but they were the spec sheet of a real processor in 1988.

Connections are all 1/4-inch tip/sleeve phone jacks: inputs, outputs, and a defeat jack that accepts any on/off toggle switch, closed to enable bypass. MIDI In and MIDI Thru are on 5-pin DIN. The front panel has a signal detect LED in green and a processed-signal overload LED in red, which is more status feedback than most budget processors of the era offered.

Studio Sound (October 1988, p.24) framed the LXP-1 as Lexicon's answer to the growing low-cost digital reverb market, noting it offered 16 basic programs and could be controlled alongside up to four LXP-1s from a single remote. That program count is the working reality of the box: sixteen algorithms, not a hundred, and the design leans on quality over quantity. Mix (July 1989, p.152) ran Lexicon's own advertising copy describing the LXP-1 as "uncomplicated, uncompromised, under budget," and leaned on the company's VLSI engineering as the reason the depth and smoothness of the sound survived the price cut. That's marketing, not an independent verdict, but it matches the architecture the service manual describes — a processor built around a custom Lexicon chip rather than a generic DSP.

The ZCLK signal at U2 pin 6 should measure 4 MHz with a tolerance of ±0.5% (3,980,000-4,020,000 Hz). MIDICLK at U8 pin 9 should read 500 kHz within ±0.8% (497,500-502,500 Hz). Those are the numbers a technician checks when a unit powers up but won't run.

Working on one is straightforward by the standards of the era. Two front-panel screws and five hex nuts on the rear 1/4-inch jacks release the board, which slides out of the case toward the front with the panel still attached. The service manual's troubleshooting section points to the built-in diagnostic programs and the block diagram as the first stops. The periodic maintenance advice is simple: a soft lint-free cloth, warm water, mild detergent, and no alcohol or acetone anywhere near it. Dust gets a vacuum or a low-pressure blower, nothing more.

The LXP-1 is not a PCM 70 or a PCM 80. Those are full-rack studio processors with deeper conversion stages and expansion paths. The LXP-1 is the box you take to a gig, drop into a small studio, or hand to a guitarist who needs a real reverb algorithm without a rack. It runs on a wall transformer, it weighs three and a half pounds, and it does sixteen programs.

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