MIDI - CV
If you have one of those oldie but goodie type synths that were pre MIDI fear not you can now link it into your existing MIDI system thanks to Groove Electronics
Get into the Groove with the MIDI-2-CV and John Renwick
If you pay any attention at all to the pop charts, you'll realise that practitioners of the House and Acid styles have gone for old-fashioned analogue synthesizer sounds in a big way. With the development of polyphonic, digital, MIDI synths such as the Yamaha DX-7, monophonic, analogue, voltage-controlled synths like the Moog Minimoog, Roland monosynths and ARP Oddysey, became obsolete overnight. But, now that digital and sampled sounds have become familiar, the warm, dirty sounds of those analogue synths are back in fashion, especially for playing basslines and melodies, where lack of polyphony doesn't really matter.
In fact, you can do things with voltage-controlled analogue synths which are almost impossible with modern MIDI synths - like twiddling the sound settings as you play, transposing sequences from the keyboard and so on. Of course, to make analogue monosynths part of a MIDI system, you need a MIDI-to-Control Voltage convertor, and Groove Electronics have now come up with the most powerful and inexpensive model seen so far.
Groove's clever little box is the latest in a series of products which help you to make the most of non-MIDI synths; the company also manufactures MIDI retrofits for several old synths and Yamaha electronic pianos. MIDI-to-Control Voltage conversion isn't a new idea; companies including Vesta, UMI and Roland have tried it, but all their products are now discontinued. The basic idea, of taking digital MIDI data and turning it into analogue control voltages, is simple; but because there are so many control methods the problem becomes complicated.
The MIDI-2-CV is powerful, because it has a huge range of control options and complete programmability; and inexpensive, because you only have to pay for the facilities you need for your particular monosynth. It's a mains-powered black box with a confusing system diagram, eight squishy buttons and a row of status LEDs on the front panel. On the back is a bewildering array of input and output sockets, the number and function depending on what options you have paid for.
Obviously there's a MIDI IN, for data from your computer, sequencer or MIDI keyboard and a MIDI THRU. You also get mini jack sockets for Control Voltage Out, which sets the synth's pitch, Gate Out to actually trigger the notes and Level Out, to control the filter cut off level.
Programming the MIDI-2-CV to work with your particular synth can be a nightmare. There are eight control buttons, marked A-H, but the only indication you have of the editing mode and parameter set, is the status of the eight LEDs whether they're dark, lit, flashing slowly or flashing quickly. One of the optional extras, at £20, is a memories section which stores up to sixteen settings once you've figured them out - I heartily recommend it!
The range of parameters available for each program is huge. You can transpose pitch up or down three octaves, choose whether you have High, Low or New note priority, set any MIDI channel (though there's no OMNI mode, for fairly obvious reasons), choose whether breath control, aftertouch, mod wheel or velocity data is routed to the Level output for the synth's filter cut off and lots more. Some of which you're unlikely ever to need. To give you a decent range of pitches, MIDI-2-CV produces a bi-polar voltage output from -3 to +4 volts. Because some old synths won't respond to negative voltages, you may have to use the Transpose function to get them to work below Middle C.
There are many different operation standards for controlling analogue monosynths, MIDI-2-CV tries to cope with all of them, but it's intended mainly for those using the 1-volt-per-octave standard. As for actually triggering the notes, you can select Positive Going, Negative Going or Ground Trigger types; for Moog synths you can have S-Trigger fitted as an optional extra, or if you'e handy with a soldering iron Groove will give you instructions for converting the S-Trigger on your Moog to a more conventional type. If you don't have a manual for your antique synth, it's going to take you some time to get the system working by trial and error.
Even if you know exactly what you're doing, analogue synths normally need constant retuning to get good results. On the side of the MIDI-2-CV are calibration screws for the pitch-scaling, tuning and MIDI pitch-bend response of the synth; these should be adjusted after your synth's warm-up period.
The most attractive aspect of the MIDI-2-CV is its expandability. When you order, you can specify various options such as a complete second MIDI-to-CV channel (£25), another independent channel designed to operate the EDP Wasp/Gnat synths, which use a pre-MIDI digital keyboard scanning technique (£20), DIN-Sync, allowing you to run Roland pre-MIDI drum machines like the TR-808 from a MIDI clock and Arp Clock, which triggers arpeggiators such as that found on the Roland Jupiter 4 (£20).
If your analogue synth is one of the Korg or Yamaha types which uses the hertz/octave system, don't despair, there are two ways to convert MIDI-2-CV. You can either buy an external convertor box for £35, or have it permanently fitted for £15, and there are some exotic options, such as one which turns MIDI-2-CV into a six-channel trigger unit for Simmons-type drum modules.
Groove's plans for the future include MIDI-4-CV, a direct replacement for Roland's discontinued MPU-101 four-channel MIDI-to-Control Voltage convertor, a MIDI retrofit for the E-Mu Drumulator drum machine and other exotic items like a CV conversion for the Roland TB-303 Bassline, a MIDI-controlled lighting system, and a MIDI-controlled speech synthesizer. At the moment I'm still working through the possibilities of the marvellous MIDI-2-CV, but I can't wait!
Price: £95 + optional extras (see text)
Supplier: Groove Electronics, (Contact Details)
Review by Chris Jenkins writing as John Renwick
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