MIDI-to-CV converters don't come much cheaper - or more flexible - than this one. Tim Goodyer tests the latest addition to Tantek's ever-expanding rack.
IN A VALIANT effort to reconcile pre- and post-MIDI technologies, some bright spark conceived the idea of a "black box" whose purpose in life it would be to translate MIDI information into good, old-fashioned control voltages and gates - the MIDI-to-CV converter. And the idea caught on. Roland have one, the MPU 101; Jellinghaus have one, the CG-X; and now Tantek have one.
First of all, it's worth mentioning that the Tantek MIDIverter won't work as a stand-alone unit. It's been designed as part of Tantek's Tanrak system, a 4U-high, 19" rack-mounting frame that houses effects like DDLs, gates, modulation oscillators, and so on.
MIDI data is input from the controlling MIDI keyboard via a MIDI In socket on the front panel, and is made available at a MIDI Thru below, allowing chaining for control over further synths, synth modules, or Tantek's own Digital Sampler module.
In addition to the MIDI sockets, the simple front panel offers Velocity Shape and Trim controls, a couple of LEDs, and a Channel button. There are also a few trimpots for setting up, but most of that is done on trimpots and switches on the circuit board inside.
The MIDIverter makes available a surprising number of setup options, covering everything from note priority and triggering polarity to MIDI default channel and polyphonic chaining.
Calibration of the MIDIverter to your chosen CV/Gate synth is a fairly simple but essential preliminary to use, because analogue synths vary so much from unit to unit. A small screwdriver applied to the trimpot marked "V/oct' easily settles any differences of opinion.
The MIDIverter will operate on all 16 MIDI channels, and selection is made by pressing the Channel button and inputting data on the desired MIDI channel. The unit then searches for an active MIDI channel and locks onto it, though there's no indication of which channel it has selected. Pressing one note also selects Mono, while pressing more than one note gives you Poly mode.
A single MIDIverter module will extract two sets of CV/Gate information from an incoming MIDI data stream. In addition to these, it derives a second control voltage from key velocity information for control, for example, over VCF cutoff frequency or VCA level. All the control outputs are on five rear-panel jacks, CV2 and Gate2 being derived from CV1 and Gate1. The Gate is a straight duplication, but CV2 is proportional to CV1, variable between 0-100%. As the users' manual suggests, these can be used for synths not tracking at 1V/octave to eliminate compatibility problems, or as a straight duplicate output for tracking a synth line in unison. The pot resolution is finer at the 100% end - to make accurate adjustment easy - and coarser lower down the scale where it is more likely to be used as a "special effect". The section can also usefully be routed to the VCF Cutoff Frequency for keyboard tracking purposes, and even though a keyboard tracking at 62% of the 1V/oct standard will give you a pretty weird scale, it will at least provide you with an answer when your next-door neighbour gets an updated DX7 with microtonal tuning...
Key velocity information appears at only one output of the MIDIverter, and is processed first by the Velocity Shape pot: this governs the CV response to lower velocity values. At its most active extreme, the CV output completely cuts off at low velocity values, while at the other extreme, the velocity is made to appear constantly at maximum. If you can't find a satisfactory setting between these two values, you're probably playing with your feet.
Assuming you're using more standard methods of creating music - a sequencer or even your fingers - the MIDIverter performs well. Should your analogue synth not provide you with access to VCF cutoff frequency or VCA level, you can route velocity information to another of Tantek's toys, the Fader-Panner. This can be configured to give, among more dramatic effects, a straight volume response to playing dynamics.
A bonus feature of the MIDIverter is its ability to "clean up" MIDI data. The notorious cumulative MIDI Thru delay is not usually a delay as such, but rather a progressive degradation of MIDI data. To alleviate this, regeneration circuitry has been incorporated into the MIDIverter's design. Although this necessarily does involve a delay, this should only amount to 300 microseconds per MIDIverter unit, so the feature could prove useful if you have to use a long MIDI chain.
Prices MIDIverter £169.95 (assembled); Mother unit £99.95 (assembled), £79.95 (kit); all including VAT