Introduced in 1984, the Publison Infernal Machine 90 Stereo Audio Computer was an advanced dual-channel digital audio processor combining delay, echo, pitch-shifting, reverberation, sampling and time manipulation within a single programmable studio system. Developed and manufactured in France, the Publison Infernal Machine 90 brought together functions that would normally have required several separate processors, while its expandable memory, MIDI control and optional synchronisation facilities allowed it to develop into a remarkably capable digital production workstation.
The Publison Infernal Machine 90 followed Publison’s earlier work in digital pitch-shifting and delay processing, but greatly expanded the concept. Rather than concentrating upon a single effect, it was designed as a general-purpose stereo audio computer with two separately configurable processing channels. Each channel could be assigned its own function and parameter settings, allowing the Publison Infernal Machine 90 to perform two different processing tasks simultaneously. One channel could, for example, provide pitch-shifting while the other generated reverberation, delay, echo or sample playback.
Two electronically balanced audio inputs fed the digital processing system, while four electronically balanced outputs supported the machine’s dual-channel and stereo processing architecture. The analogue-to-digital and digital-to-analogue sections used 16-bit linear conversion, with a quoted dynamic range of 95dB. In delay mode, the Publison Infernal Machine 90 provided a frequency response of 20Hz to 20kHz within ±0.3dB, while its reverberation processing operated from 20Hz to 10kHz within the same tolerance.
The front panel was dominated by a numerical keypad, function controls and alphanumeric displays. Functions were selected by entering their corresponding numerical codes, after which individual parameters could be recalled and edited. Values could be entered directly from the keypad or adjusted progressively through what Publison called Potentiometer Mode, in which the keypad’s plus and minus controls acted as a variable parameter control.
An integrated electronic user guide was displayed automatically after power-up and could also be called at any time from the front panel. The guide presented operating instructions and a table of available functions directly on the machine’s display, reducing the need to consult the printed manual while programming. This was particularly useful because the Publison Infernal Machine 90 contained numerous functions, parameters and operational modes that extended far beyond those of a conventional effects processor.
Delay and echo processing
The standard Publison Infernal Machine 90 provided delay times from 0.02ms to approximately 5,242ms. Delay values could be entered numerically with fine resolution, allowing the machine to be used for everything from very short phase and modulation effects to extended rhythmic delays.
The separate echo function added digital feedback adjustable from 0 to 99 per cent. Delay time and feedback could be set independently, making it possible to create conventional echoes, closely spaced repeating effects, long recirculating delays and effects approaching continuous regeneration.
Because channels A and B could be configured separately, different delay times or effects could be applied to two signals at once. The four-output arrangement also supported processing configurations in which each channel generated a stereo output.
Pitch-shifting and time manipulation
Pitch-shifting was one of the central functions of the Publison Infernal Machine 90. Two independent pitch-processing channels provided a range extending from two octaves below the original pitch to one octave above it. Publison supplied different processing algorithms intended for complex sounds, human voices, strings and other programme material.
Pitch ratio and additional delay could be adjusted independently, allowing the Publison Infernal Machine 90 to create harmonies, double-tracking effects, detuning, octave processing and delayed pitch-shifted repeats. The availability of two independent channels made it possible to produce two-part harmonies or combine different pitch intervals and delay times.
Later operating software added functions including evolving vibrato and automatic arpeggiation. Evolving vibrato provided control over modulation frequency, depth, delay and operating mode. Automatic arpeggiation combined pitch alteration with recirculating delay, producing successions of transposed notes from a single incoming sound.
The Publison Infernal Machine 90 could also alter pitch independently of duration. This allowed recorded material to be shortened or lengthened without producing the corresponding change in pitch associated with conventional variable-speed playback. Conversely, pitch could be altered without proportionally changing the duration of the sampled sound.
Reverberation
The Publison Infernal Machine 90 incorporated two independent stereo reverberation processors. Users could select from 52 factory reverberation programmes or construct effects through the parametric reverberation function.
The parametric reverberation system provided control over simulated room size, reverberation time, predelay, attenuation, frequency-dependent decay and primary reflections. Room size could be selected from 1m³ to 1,000,000m³ across 13 steps, while decay time extended from 0.1 to 200 seconds.
Predelay was adjustable from 1 to 999ms in 1ms increments. Separate low-frequency and high-frequency decay coefficients allowed the decay characteristics of different parts of the frequency spectrum to be modified independently, with each coefficient adjustable from 0.25 to 4.00.
Three primary reflections could be programmed individually. Each reflection had its own delay setting from 1 to 999ms and attenuation from 0 to 99dB. These parameters allowed the initial reflection pattern to be shaped separately from the later reverberant decay.
Sampling and sound memory
The sound-memory section turned the Publison Infernal Machine 90 into a programmable digital sampler. Its standard memory configuration provided approximately 5.24 seconds of recording time for each of its two channels at a 20kHz frequency response. An expanded configuration increased this to approximately 20.96 seconds per channel.
Sampling could be initiated from the front panel, MIDI or an incoming audio signal. The Publison Infernal Machine 90 supported triggered recording, multisampling, looping and the assignment of different samples across a MIDI keyboard. Samples could be organised into chromatic stacks, allowing recordings to be selected and transposed from incoming MIDI notes.
Sample start and end points could be edited, while loop boundaries allowed selected portions of a recording to repeat. Playback could run forwards or in reverse, and controls were provided for pitch ratio, playback speed and attack time. Pitch and duration could also be adjusted independently through the time-compression and time-expansion functions.
The sampling system was not limited to playing a single recording at different pitches. Its multisampling facilities allowed several recordings to be stored and assigned to different MIDI note ranges, reducing the amount of transposition required from any individual sample.
Memory and programme storage
The standard Publison Infernal Machine 90 contained 150 non-volatile function memory locations for storing combinations of functions and parameter settings. An optional expansion increased this capacity to as many as 700 locations.
Stored programmes allowed complete processing configurations to be recalled without manually re-entering every value. This was particularly important in professional recording and post-production environments where complex delay, pitch, reverberation and sampling arrangements might need to be reproduced at a later session.
Publison continued to expand the sound-memory capacity throughout the production life of the Publison Infernal Machine 90. Early options provided approximately 20.96 seconds per channel, while later solid-state memory boards offered approximately 83 seconds per channel or 166 seconds when configured as a single channel, while retaining 16-bit operation and a 20kHz frequency response.
Hard disk recording and digital editing
By 1988, the Publison Infernal Machine 90 could be fitted with an internal hard disk board providing up to 14 minutes of digital audio recording. The hard disk could store the machine’s sampling memories and their associated parameters, record stereo audio directly and support digital editing.
An external digital cassette unit could be connected through the SCSI interface to back up the contents of the internal hard disk. This gave studios a removable method of archiving sampled and edited sounds while allowing the hard disk to be reused for other projects.
These additions moved the Publison Infernal Machine 90 beyond the role of a conventional effects processor. Equipped with expanded memory, hard disk recording and digital editing, it could function as a compact digital audio production system for sampling, processing, editing and synchronised playback.
MIDI, synchronisation and remote control
MIDI formed part of the Publison Infernal Machine 90’s control and sampling architecture. It could be used to trigger samples, select recordings, control chromatic multisample arrangements and integrate the machine with keyboards, sequencers and other MIDI equipment.
An optional SMPTE/EBU interface provided synchronisation with audio and video equipment. The synchronisation system also supported automatic pitch tracking on two completely separate processing channels, allowing pitch operations to follow externally controlled production events.
Machines fitted with the appropriate hardware could also support RS-232 computer control and optional digital audio inputs and outputs. These interfaces reflected the modular construction of the Publison Infernal Machine 90, which was designed to accept new boards and operating software as additional functions became available.
An optional dedicated remote controller reproduced the machine’s displays and numerical controls away from the main rack. It also incorporated an endless optically encoded parameter control, providing a more direct method of changing values than repeated keypad operation.
Construction and continuing development
The Publison Infernal Machine 90 used a modular internal design with circuit boards mounted on guides. This construction allowed boards to be replaced, serviced or upgraded as Publison introduced new memory, interface and processing options.
Its capabilities changed substantially during its production life. New software introduced additional sampling, pitch, modulation and synchronisation functions, while new hardware increased programme storage and audio recording capacity. Publison promoted an upgrade service that allowed earlier machines to receive later boards and operating software rather than becoming fixed at their original specification.
This continuing development makes it important to distinguish between the standard Publison Infernal Machine 90 and machines equipped with later options. Sampling time, programme capacity, computer control, digital interfacing, SMPTE synchronisation and hard disk recording depended upon the installed hardware and software revision.
Legacy
The Publison Infernal Machine 90 became associated with high-end recording studios and productions requiring detailed pitch manipulation, unusual vocal processing, reverberation, extended delay and flexible sample playback. It was used during the era in which sampling was becoming a central production technique, but before large-memory samplers and computer-based digital audio workstations became widely accessible.
The Publison Infernal Machine 90 has been connected with recordings including Madonna’s Like a Virgin, Joe Jackson’s Big World, Rick Astley’s Never Gonna Give You Up, Chris Isaak’s Wicked Game and Cher’s If I Could Turn Back Time. It also remained part of the equipment collection at AIR Studios in London.
Its combination of independent dual-channel effects, programmable reverberation, pitch-shifting, time compression and expansion, multisampling, MIDI operation and later hard disk recording placed the Publison Infernal Machine 90 among the most extensively configurable digital audio processors of its period.
Features
- Two separately configurable digital audio processing channels
- Independent delay, echo, pitch-shifting, reverberation and sampling functions
- 16-bit linear analogue-to-digital and digital-to-analogue conversion
- Two independent stereo reverberation processors with 52 factory programmes
- Two-channel pitch-shifting from two octaves down to one octave up
- Multisampling with MIDI triggering, looping and keyboard sample assignment
- Independent control of sample pitch and duration
- 150 standard non-volatile programme locations, expandable to 700
- Expandable solid-state memory and optional 14-minute hard disk recording
- Optional SMPTE/EBU synchronisation, digital audio interfaces and remote control
