Lexicon PCM42 (1982)

A third-generation digital delay that put up to 800 milliseconds of clean, true-PCM delay in a rack-mount box. It also gave performing musicians foot control over all of it.

Overview

The PCM42 is a Digital Delay Processor. Lexicon's own manual calls it "a compact third-generation system" capable of up to 800 milliseconds of high-performance audio delay. That 800 ms figure only shows up in the DLY X2 mode at a reduced 6 kHz bandwidth. In X1 mode the unit gives you 200 milliseconds at full bandwidth, or 400 milliseconds at 6 kHz. The delay taps are the real story. There are eleven pushbutton-selected taps at 0, 0.8, 1.6, 2.4, 4, 7.0, 12, 26, 50, 100, and 200 ms in X1 mode (doubled in X2), and each one is continuously variable over a 4:1 range via the Delay Multiply control. Discrete taps plus continuous adjustment is what separates this from a fixed slap-back box.

The manual is explicit about the design philosophy. Lexicon's engineers rejected analog bucket-brigade delay, Delta Modulation, and other quasi-digital techniques in favor of true Pulse Code Modulation, which the manual describes as "a signal encoding technique widely preferred by professionals." Quoted frequency response is 20 Hz to 15 kHz, +0/-1 dB in X1 mode. Total distortion and noise is 0.04% typical and 0.07% maximum at 1 kHz in X1, and dynamic range is better than 90 dB across a 20 Hz to 20 kHz bandwidth. Lexicon's own copy claims the PCM42 "out performs even the more expensive competitive models" thanks to cost-effective implementation of PCM. That is a marketing claim, not an independent verdict, but the numbers back the pitch.

The front panel is divided into INPUT, DELAY, and VCO functional groups. Controls are differentiated by both color and shape so a performer can find settings quickly on a dark stage. The VCO section is where the PCM42 gets strange. Modulation depth sweeps from zero to a 4:1 range of delay time, rate runs from 0.1 Hz to 10 Hz, and an LED flashes to show the modulation rate. The VCO shape control blends continuously between sine and envelope, or square and envelope. The envelope follower lets time modulation track the input signal itself.

Rear-panel connectivity is more serious than the compact chassis suggests. The input is a balanced differential design on a 1/4-inch Tip-Ring-Sleeve jack, with 40 dB of common-mode rejection and 40K ohms impedance. It accepts unbalanced sources too. An adjustable input level control plus a 20 dB gain switch on the rear panel handle maximum input levels from -23 dBV to +19 dBV (0.07 V to 9 V rms). The Main Out is unbalanced on a 1/4-inch Tip-Sleeve jack with 100 ohms actual source impedance. It delivers up to +19 dBV (9 V rms) into loads of 2K ohms or greater. It will drive down to 600 ohms, though maximum output level drops to roughly 5 V rms (+14 dBV) in that case. The Direct Out sits at 600 ohms and depends only on input level and the gain switch. With headroom indicating 0 dB, it puts out +11 dBV (3.5 V rms). A rear-panel Bypass jack shorts Tip to Sleeve to drop the unit out of the chain.

The feature list reads like a wishlist for the working musician. It has input/delay mixing with recirculation (feedback), switchable polarity inversion of both the feedback and delay signals, and high-pass and low-pass filters. Foot-control jacks let a performer switch the effect in and out, capture and indefinitely repeat a musical phrase, and control the VCO time base in sync with the music. The manual also documents the PCM42 as a companion to Lexicon's Model 93 PRIME TIME processor, with series, parallel, and feedback interconnection schemes illustrated.

Period reception was strong. Mix (January 1983, p.34) ran a feature under the headline that Long View Farm had discovered a new range of effects with Lexicon's PCM-42. It quoted chief engineer Jessie Henderson calling it "without question, the highest performance processor in the digital effects market" and praised the long delays, clean sound, and metronome clock. Recording Engineer (June 1983, p.26) carried the same Long View Farm piece, highlighting the long delay loops, sound-on-sound effects, input-overload protection, and the advanced analog/digital encoding behind the unit's clean sound. Studio Sound (September 1983, p.17) framed the broader PCM series as having "revolutionised the creation of" dramatic stage and studio sounds. It listed automatic double tracking, flanging, slap echo, infinite repeat, and doppler pitch shift among the available effects, plus comprehensive foot-pedal control for live performance and a numeric display showing exact delay time at any instant. The same advertisement reappeared in Studio Sound (January 1984, p.15) with the added line that the system was "virtually distortion free over the entire" operating range.

That numeric delay-time display is worth a closer look. Most delay units of the era made you count knob positions. The PCM42 gives a readout of the exact delay time at any instant, so you can dial in a specific doubling time, note it, and come back to it. Combine that with the eleven calibrated taps and the 4:1 continuous range on each, and you have a lot of repeatable control.

The manual's own warranty section shows what ownership involved. Lexicon warranted each PCM42 free from defects in material and workmanship for one year from delivery. The warranty was void under abuse, neglect, alteration, unauthorized repair, improper use, incorrect power source, or damage from accident, act of God, war, or civil insurrection. The manual also notes Lexicon reserved the right to make design and construction changes without obligation to update units already sold, so not every PCM42 is identical inside. Replacement parts and the service manual could be ordered from Lexicon, Inc. at 60 Turner Street, Waltham, MA 02154. The company warned that units shipped back for service travel at the owner's risk unless well packed and insured, with accessories like power cords, manuals, and remote switches left out of the box. The unit carries hazardous voltages under both the top and bottom covers, so servicing is strictly a qualified-technician job.

Anyone buying one today should expect to verify the power-supply condition and the state of the rear-panel jacks, and should treat the foot-control and remote-switch accessories as frequently missing. The sound — true PCM, better than 90 dB dynamic range, and a VCO section that tracks the input envelope — is why the PCM42 has stayed in racks for four decades.

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Lexicon PCM42 (1982)

Overview

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