by Mike Perkowitz

Every electronic musician these days is familiar with MIDI, the digital interface standard that allows remote control, synchronization, and data transfer between all sorts of synths, drum machines, samplers, sequencers, computers, and so on. MIDI has been around for about 12-15 years now, but before MIDI there were a number of other ways of doing some of these tasks. This article discusses some of these pre-MIDI control methods, from CV/Gate to DIN sync to DCB.

An outline of the article:

• CV/Gate
• DIN Sync
• Triggers
• Other Proprietary Interfaces

There were a number of variations on the basic CV/gate interface. Probably the most widely-used was the standard used by Roland. Roland CV was an exponential voltage signal of 1v/octave -- adding another volt to the signal raised the pitch an octave. The Roland gate is a positive going signal, called a voltage trigger (or v-trigger) that is usually low and goes high as long as the note is held down. Roland synths such as the SH line (except the SH-3), the TB-303, and the MC-202 and MC-4 all used this standard. Oberheim also followed this standard in their analogue synths, including the Xpander (which had MIDI as well as CV inputs) and their SEMs, which can be modified to take CV inputs. Some later Korg analogues were also compatible -- the Mono/Poly, for example, uses 1v/octave CV and has a gate switchable between v-trigger and s-trigger. Both Sequential and Arp also followed this standard.

Though they used 1v/octave CV, Moog synths, instead of a v-trigger, used s-trigger -- a gate which is, approximately, an upside-down v-trigger. And instead of the more typical 1/4" or 1/8" jacks, Moog tended to use a Cinch-Jones connector for CV/gate. Earlier Korg equipment used the s-trigger as well, but with linear CV which was incompatible with almost everybody else.

Other variations existed. The EML 101, for example, used 1.2v/octave and v-trigger. The Roland SH-3 (which has no CV/gate inputs but can be modified) used approximately 1.2v/octave and s-trigger.

If you have a synth that takes CV/gate inputs, you have two basic options for how to control it: you can use a CV sequencer, or you can use a MIDI->CV convertor. CV sequencers include the MC-202 and the MC-4 from Roland. The Korg SQ-10 was designed to go with their MS-10, MS-20, and MS-50. Arp produced a sequencer which quantizes its output to proper semitone values. The latest version of Doepfer's MAQ 16/3 has CV and MIDI outputs.

Many MIDI->CV convertors have been made over the years. Roland once produced the MPU-101, which provides four channels of CV/gate output. Paia used to make an inexpensive kit, and are putting out a new one. Kenton, well known for MIDI retrofits, produce the Pro-4, Pro-2, and Pro-Solo -- all MIDI->CV convertors with plenty of functionality. Several recent analogue synths, such as the Novation BassStation Rack, the Paia Fatman kit, and the Syntecno T-303 feature built-in MIDI->CV convertors as well.

DIN Sync

Roland and Korg both used an interface known as DIN Sync for synchronizing drum machines and sequencers. DIN Sync is named for the 5-pin DIN connector used; it's the same connector used for MIDI, but DIN Sync is an entirely analogue interface and, of course, is not at all compatible with MIDI. DIN Sync provided a basic 24 or 48 pulse-per-quarter-note (ppqn) signal, as well as start/stop controls. Roland's DIN Sync machines used a 24ppqn clock, and include the TB-303 (input only), TR-606, TR-808, CR-8000, MC-202, and TR-909 (input only). Korg equipment such as the DDM-110, DDM-220, and KPR-77, however, used a 48ppqn clock. If you sync Korg and Roland together, the Korg will run at half speed.

A number of machines exist that can convert between MIDI clocks and DIN Sync clock. The Korg KMS-30 has MIDI in/out, Sync in/out, and tape in/out. Any of the three can be the master clock, and the Sync connections are all switchable between 24ppqn and 48ppqn. The Roland MSQ-100 and MSQ-700, though both intended primarily as sequencers, can both convert between MIDI and Sync clock. The Roland SBX-10 and SBX-80 are both intended as dedicated sync boxes and offer more features. Kenton's Pro-4 also outputs DIN Sync clocks from a MIDI signal. Garfield also made dedicated sync boxes; the Masterbeat, for example, offers a bewildering variety of sync options.

Triggers

Another means of synchronizing synths, drum machines, and sequencers was the humble trigger. A trigger is much like a gate, except that it was typically a momentary pulse instead of being held. Synthesizers with arpeggiators often have a clock input for the arpeggio notes; every time it gets a trigger, it plays the next arpeggio note. Really ancient drum machines can often be modified to take trigger inputs for their sounds or to clock to an external trigger. A trigger can also be sent to the gate input of a synth. Many old drum machines and sequencers put out trigger signals (some of them programmable, some simply on every 8th or 16th note). Sometimes an audio signal (like a short, loud drum hit) can also serve as a trigger.

As with gate, triggers come in v-trigger and s-trigger. Most equipment uses a v-trigger, but occasional triggers (the arpeggio input on the Korg Mono/Poly, and the trigger output on the Korg DDM-110, for example) are s-trigger.

Other Proprietary Interfaces

Shortly before the appearance of MIDI, Roland came up with their own digital, polyphonic control system, known as DCB. DCB only appeared on two synths (the Juno-60 and Jupiter-8), a sequencer (the MSQ-700), and a MIDI->DCB convertor (the MD-8). DCB provides basic note on/off control similar to MIDI. Although the MSQ-700 can do MIDI and DCB sequencing, it cannot do both at once, and it cannot sync to MIDI while sending DCB (but it can sync to DIN Sync). Kenton's Pro-4 also converts from MIDI to DCB.

Oberheim used some control system of their own for a while as well. The OB-8, OB-X, OB-Xa, DSX, and DMX all used it. In fact, you can only enter sequences into the DSX sequencer via this interface using an OB-8, OB-X or OB-Xa.