EMS Vocoder 2000
Sixteen bands of British analysis and synthesis, and the ability to make an organ talk.
Overview
The EMS Vocoder 2000 is not a synthesizer in the usual sense. It is a signal processor with two inputs, a "speech" signal and an "excitation" signal, and one output. The output carries a proportion of the harmonic structure of the excitation combined with the formant structure, or articulation, of the speech. Patch speech and an organ together and you get a talking organ. Patch speech and a guitar and the guitar starts to form words. Tim Orr designed it for Electronic Music Studios of England, and the service documentation he wrote for it is dated May 1977.
The core is an analyzing and synthesizing filter bank built from two mirror-image sets of 16 band-pass filters with identical center-frequency tunings. Speech is analyzed into 16 frequency bands covering the audio spectrum, and an envelope follower pulls out the time-varying energy level in each channel. The synthesis side uses 16 voltage-controlled multipliers. The time-varying spectrum of the speech is imposed on the excitation, so the excitation is filtered in a way entirely prescribed by the speech signal. That is the whole trick, and it is a good one.
EMS built the Vocoder 2000 as professional studio equipment, and the market treated it that way. It shows up alongside large-format consoles rather than bedroom synthesizers, and dealers listed it at $53,950 in 1978. Recording Engineer (October 1978, p.119) carried the dealer listing at that price. That money buys serious analysis and synthesis hardware.
Two internal excitation sources are built in: a noise source and a 0-1 kHz pulse-wave oscillator. Recording Engineer (February 1978, p.86) noted that unvoiced sound can be restored through the internal noise source. That is the practical answer to sibilance, the 's' and 'sh' sounds that carry so much of speech intelligibility. The machine also has a voiced/unvoiced detector, a low-pass filter, and a range of modulation options, plus controls for slew freeze and pause stuffing.
Key Features
16-Band Analyzing and Synthesizing Filter Bank
Sixteen channels of vocoding, confirmed across multiple sources. The analysis section splits the speech signal into 16 frequency bands spanning the audio spectrum, and the synthesis section applies those band energies as control voltages to the excitation. The two halves use mirror-image filter sets with matched center frequencies, which lets the spectral envelope of the speech transfer cleanly to whatever you feed in as excitation. The filter bank runs on the CA3080, an RCA transconductance amplifier with no direct equivalent. Anyone who has to keep one of these running today cares about that part a great deal.
Each analysis channel has a variable slew rate envelope follower, and the synthesis side uses voltage-controlled multipliers. The slew is not a fixed time constant. It is adjustable, and it is one of the reasons the Vocoder 2000 has a reputation for sounding smoother than simpler vocoders of the period.
Dual Input Architecture: Speech and Excitation
Two inputs, one output. The speech input accepts mic or line level and has a Speech Level control, with pre-emphasis applied to lift the top end before analysis. The excitation input takes whatever you want to make talk: organ, guitar, synth, another voice. A switch routes the internal VU meter to either the speech or the excitation signal, so levels can be set without guessing. The machine never makes sound on its own through this path. It only imposes one signal's articulation onto another.
Internal Noise Source and 0–1 kHz Pulse Oscillator
The Vocoder 2000 carries its own excitation sources, so it does not strictly need an external carrier. The noise source is generated by a zener diode and can run continuously, be gated on by the unvoiced decision, or be switched off entirely. The oscillator produces a pulse waveform that can run continuously, be gated on by the voiced decision, or be switched off. Pitch can be set manually or varied by a control voltage generated from the filter bank analysis. A voiced/unvoiced detector watches the speech signal and decides whether a given moment is voiced (derived from vocal cord vibration) or unvoiced ('s' sounds), and those decisions drive the internal sources. There is also an 'S' generator switch that alters the external excitation signal to make it more sibilant.
Slew Freeze and Pause Stuffer
The slew freeze section controls the synthesis filter bank directly. Freeze the control voltages and the formant structure stops moving, so the vocoder holds a fixed vowel shape. Slew the control voltages heavily and the output turns smeared and reverberant, because the information in the filter bank is being time-blurred. Two smearing modes are available: symmetrical, where a sound takes as long to build as it does to decay, and asymmetrical, where the filter bank loads immediately and then decays slowly. These are not subtle effects.
The pause stuffer addresses a practical problem. When you vocode orchestral music, the amplitude dynamics of the speech create big gaps in the output. The pause stuffer fills those silences by fading up the music signal and fading it back down the moment the vocoder output returns. Speech or excitation can trigger the stuffing, and there is a choice of fade-in times. The output mixer selects between the vocoder output, the speech signal, or the external excitation, and any of these can be controlled by an external swell pedal.
Historical Context
The Vocoder 2000 was developed from the earlier EMS Vocoder 5000, which reached the market in 1975. The 2000 followed in the late 1970s, with one source dating it from 1977, the same year as the Tim Orr service manual. EMS built it in England alongside the VCS3. The company is best known for that synthesizer, but the vocoder was a different kind of product aimed at a different buyer.
The machine's most famous public appearance is in the original Battlestar Galactica, where the Cylon Centurions' voices were produced with an EMS vocoder. A 16-band vocoder with a pulse oscillator and a noise source does that metallic, imposing delivery well. Mark 1 units were built in discrete component form, the very first model in the line, and at least a handful of units left the factory with Mk1 faceplates and VU meters paired with upgraded circuitry to improve performance. Variants exist, including a black edition, and units turn up set for both 110V and 240V depending on where they originally lived.
Collectibility & Value
The Vocoder 2000 is rare. One dealer describes it as a very rare EMS 2000 Vocoder, and the same source notes it as one of a handful of units made by EMS. Market activity is thin: the instrument changes hands only about three times a year, so most surviving units are probably sitting in studios and collections. A Soundgas listing priced one at £5,250 including VAT, or £6,300 with VAT. For historical comparison, one owner reported acquiring theirs in 2002 for around 2,300 euros, describing it as a big luxury even then. Synth-DB and Vintage Synth Explorer both call it an excellent voice synthesizer comparable to the Roland SVC-350, and owners use words like legendary without much prompting.
Servicing is the practical concern. Tantalum and electrolytic capacitors are the known weak point. At least two dealers report replacing them as routine preventative work, and one unit was described as having all tantalum and electrolytic capacitors replaced during a recent service. Another had its power supply capacitors swapped preemptively. One unit was checked over and calibrated by EMS Cornwall and given a clean bill of health. The CA3080 at the center of the filter bank has no equivalent, so anyone buying one should confirm the filter bank is fully functional before committing. The Tim Orr service manual exists and is the reference document for keeping these alive.
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