![]() Two versions of the keyboard mechanism were used early production units had "J-wire" key contacts, while later ones had membrane switches under the keys. ![]() The wood case solved the case structural issues, and looked a lot nicer too. ![]() At one time, an elegant solution to the case flex problems existed in the form of an aftermarket wood case, to which the synth's guts could be transplanted. Over the years, a number of modifications have been offered most common ones are CPU replacements which provide capabilities such as expanding the sequencer memory, and MIDI retrofits. And, oddly, none were ever produced with MIDI, despite the production run overlapping with the introduction of MIDI. Patch memory was omitted, even though the Pro One was sufficiently complex that it could have used it (and it was a CPU-controlled synth). The plastic shafts of the pots sometimes broke if the knobs were manipulated aggressively, and the power supply transformers tended to break away from the circuit board if the unit was handled roughly. Unlike the more expensive Prophet, the Pro One was enclosed in a plastic case the panel board was fastened directly to the underside of the case, and could be damaged by flexing of the panel face. A "drone" switch held the gate inputs to the envelope generators in the "on" state, such that the EGs would remain in the "sustain" phase indefinitely, until switched off.Īt the time it was released, the Pro One received some criticisms for some of its cost-saving measures. The gate could be controlled by the LFO, so as to retrigger the envelope generators at the LFO rate. The synth could be controlled by a pair of CV/Gate external inputs the external control voltage was added to any inputs from the keyboard or pitch wheel. The Pro One provided several alternate control modes. There was no way to edit or save a sequence. Note recording was by step entry only, and the duration of all notes was controlled by the LFO rate (or an external clock input). The sequencer was very simplistic it stored two sequences containing a total of 40 notes shared between the two. The arpeggiator could be "latched" in this mode, it would continue to play the current arpeggiation after the performer removed his/her hands from the keyboard, until switched off. The arpeggiator had two patterns: "up" and "up/down" (alternating). ![]() If no destination was connected to the mod wheel bus, the mod wheel did nothing.Īn arpeggiator and sequencer were provided. Each of these could be driven by the mod-wheel bus, the non-mod-wheel bus, or neither. Five destinations were available: the VCO A and B frequency modulation inputs, the VCO A and B pulse width modulation inputs, and the filter cutoff frequency modulation input. It allowed three signal sources - the LFO, the filter envelope generator, and the output of oscillator B (which was switchable to an LFO range) to each be routed to one of two modulation busses, one of whose overall level was controlled by the mod wheel, and one of which bypassed the wheel. One important difference was the "modulation matrix" section, which took the place of the Prophet's "poly mod" section, but served a similar purpose. The Pro One was packaged in a smaller case than the Prophet, with a three-octave, C-to-C keyboard and conventional pitch and mod wheels. The circuitry used the same Curtis IC's as the Rev 3 Prophet-5, and most of the controls were the same. Sequential tried to make the Pro One smaller, lighter and less expensive to build, while retaining the voice architecture and the basic sound of the Prophet-5, which was in demand at the time.Īccordingly, the Pro One's voice architecture was basically that of one voice of a Prophet-5, with two VCOs, a four- pole, low pass VCF, a VCA, two ADSR envelope generators to control the VCF and VCA, and an LFO. This was one of several efforts Sequential made to try to reach a market at a lower price point than that of the Prophet-5, which was quite expensive in its day. Sequential Circuits Pro One, courtesy of Ī monophonic, analogue synth produced by Sequential Circuits in the early 1980s. ![]()
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