The Lexicon PCM 91 is widely considered a gold-standard hardware digital reverb unit. Built on Lexicon's legendary proprietary algorithms, it remains a studio staple for engineers seeking deep, lush, and expansive reverberation—particularly for vocals, orchestral instruments, and ambient soundscapes.

Core Verdict & Sonic Character

• The "Lexicon Sound": Famous for its rich, thick, and polished spatial tails. Rather than striving for absolute photorealistic room acoustic simulation, the PCM 91 delivers a high-class, glossy "album-ready" space that blends seamlessly into complex mixes without sounding muddy or cluttered.

• Pure Reverb Focus: Unlike its sister unit, the PCM 81 (which focuses heavily on pitch-shifting and multi-effects), the PCM 91 devotes all of its processing power exclusively to reverberation algorithms (Plates, Halls, Rooms, Chambers, and Ambience).

Strengths & Notable Features

• High-Density Hall & Plate Algorithms: The unit excels at long, dense decay tails. Its Hall and Plate presets are legendary for creating an immersive sense of space without masking the dry signal's core detail.

• Dual-Engine Architecture: Features flexible routing configurations (Cascade, Separate, Mono Split, Dual Mono) allowing you to run two independent reverb algorithms simultaneously or chain them together for complex spatial textures.

• Flexible I/O Connectivity: Equips both balanced analog XLR/TRS inputs and outputs alongside digital I/O (AES/EBU and S/PDIF), making it easy to integrate into modern hybrid DAW or digital console setups.

• Deep Dynamic Control: Includes extensive parameter editing, keyable dynamic modulation, and tempo-sync options that allow reverb decay or parameters to react dynamically to input signals.

This unit has serial number L0898-1967 indicating it was made in August of 1998.

The PCM 91 Digital Reverberator offers Lexicon's highest quality reverbs in a compact, affordable package with a powerful interface which allows both easy access and a wealth of programming capabilities for the sound designer. All of the features of the acclaimed PCM 90 are included, plus full AES/EBU I/O, new Dual Reverb algorithms, and new presets with dynamic spatialization effects for 2-channel or surround applications.

All of the Dual Reverb algorithms and presets (available for the PCM 90 on a PC card) are built into the PCM 91. 450 presets provide sounds for real-world applications? and a unique KeyWord search and sort function allows you to find the preset you want fast. A PCM CIA card slot allows you to store your own programs on memory cards.

Features at a Glance

• All of the features of the PCM 90 PLUS built-in Dual Reverb
• AES/EBU and S/PDIF I/O
• 15 Algorithms: 5 Stereo and 10 Dual Reverb
• 450 Preset programs;
• 100 User Dynamic spatialization effects for 2-channel or surround applications

Standard Features

• Lexicon's "greatest hits" reverb algorithms of the last decade including Random Hall, Random Ambience, Rich Plate, Concert Hall and Split Chamber
• Balanced Analog I/O- XLR and 1/4" inputs and outputs
• Digital I/O- S/PDIF and AES/EBU
• Keyword Search: Allows quick, intelligent search of the presets by application (i.e. vocals, drums etc.) or alphabetical order
• A front panel Adjust knob is automatically attached to one or more of the parameters you're likely to want to change in each factory tailored preset. This allows immediate modification of each preset in real time without ever going into the Edit mode.
• Pro and Go Modes: Go mode gives you access to as many as ten hand-picked parameters for any particular preset. Pro Mode allows full access to an Edit Matrix of as many as a hundred parameters.
• Greater than 110dB of Dynamic Range Dual Lexichip Architecture- These are our own propietary microprocessors, custom designed by our own chief scientists to meet Lexicon's rigorous specifications.
• PCMCIA Card Slot for software updates and user-edited preset and system set up storage.
• 50 Factory Presets and 100 Internal User registrations are standard.

• Analog Audio Input    XLR and 1/4" balanced (T/R/S)
• Input Level    -2dBu to +20dBu, balanced;<br>-22dBu to 0dBu, unbalanced
• Input Impedance    100k&Omega;, balanced;50k&Omega;, unbalanced
• Analog Audio Output    XLR and 1/4"T/R/S balanced
• Output Level    +18dBm, balanced;+4dBm, unbalanced
• Output Impedance    125&Omega;, balanced
• Digital Audio Input    XLR, AES/EBU;<br>Coaxial RCA, S/PDIF
• Format    AES/EBU, balanced;<br>S/PDIF, unbalanced
• Sample Rate    44.1kHz and 48kHz
• Digital Audio Output    XLR, AES/EBU;<br>Coaxial RCA, S/PDIF
• Format    AES/EBU, balanced;<br>S/PDIF, unbalanced
• Sample Rate    44.1kHz and 48kHz
• Conversion    24-bit A/D;24-bit D/A
• Internal Audio DSP    24-bit (PCM 81);20-bit (PCM 91)
• Frequency Response    10Hz - 20kHz &plusmn;.5dB
• Crosstalk    -55dB 10Hz to 20kHz
• THD    &lt;0.006%, 10Hz - 20kHz
• Dynamic Range    D/A:&gt;98dB typical, 10Hz - 20kHz<br>A/D:&gt;105dB typical, 10Hz- 20kHz<br>A/A:&gt;96dB typical, 10Hz - 20kHz
• MIDI Interface    5-pin DIN connectors for MIDI IN, THRU and OUT
• Footswitch    1/4"T/R/S connector for two independent momentary footswitches (system detects normal-open, or normal-closed on power up)
• Foot Controller    1/4"T/R/S connector for foot pedal(100&Omega;- 10k&Omega;impedance)
• Memory Card
• Connector    PCMCIA type l cards, 68 pins
• Standards    PCMCIA 2.0 and JEIDA 4.0
• Card Format    Up to 1MB of SRAM (attribute memory not required)
• Power Requirements    100 - 240 volts AC;50 - 60Hz;35 watts<br>Automatic switching (3-pin IEC connector)
• Remote Power In    2.5 mm 9 volts AC (not included)
• Dimensions    19" W x 1.75" H (1U) x 12" D<br>(483 x 45 x 305 mm), rack mount standard
• Weight    6.4 lbs.(2.9 kg)
• Operating Temperature    32&deg;to 104&deg;F (0&deg;to 40&deg;C)
• Maximum Humidity    95% without condensation