As we enter the second decade of the MIDI age, there are plenty of non-MIDI analogue synths still giving sterling service in studios and keyboard rigs up and down the country. The sound, the accessibility, and their current hipness are all factors in the present popularity of analogue synths. Me? I'm still into the flashing lights.

For some time now, it has been left to smaller companies to address the market for MIDI-to-CV convertors, and Kenton are well known for their high-quality retrofits to a wide range of mono and polysynths. The Pro 2 is their new stand-alone convertor, a 2-channel unit which provides enough facilities to cope with most of the analogue machines you might come across.

The Pro 2's solid case and high build quality both inspire confidence, and you won't be disappointed when you turn the unit on; the 2-digit LED display is bright and clear, and the bargraph display that indicates what parameter is being edited is just fine. I won't bore you with details; suffice to say that whilst no interface that uses a mere three buttons (Inc, Dec, and Select Option) and a simple bargraph display can be totally intuitive, you will get the hang of this very quickly.

So what does the Pro 2 do? As a dual channel unit, it will take two channels of MIDI data, and produce two sets of analogue control signals, each of which can control an SH101/Pro-1/MiniMoog, etc. Each channel has both gate and S-trigger outputs, to trigger the notes, and a CV output to control pitch. Whilst most analogue synths accept a gate control signal, Moog synths, plus others such as the Korg MS-series, require an S-trigger instead; full marks to Kenton for providing both outputs on both channels. There is an optional Hz/V output for channel 1, to enable compatibility with certain synths that do not use the 1 V/octave CV standard. The Yamaha CS and Korg MS series both use this linear voltage control system, in which the oscillator frequency is directly proportional to the control voltage.

Beyond simple note on/off and pitch control, each channel has Aux 1 and Aux 2 control outputs. These can be controlled by any MIDI controller. You'll most probably use Aux 1 to modulate your synth's filter cutoff. A second control input is less common, but where it is available you might be able to control note volume via the VCA.

Two analogue sync outputs are provided: an Arpeggio Clock output, and a Sync 24 output. The former produces a +5 volt pulse to advance analogue arpeggiators or sequencers, and you can set its 'rate' between 1 and 12 pulses per quarter note. The Sync 24 output allows connection to much vintage Roland gear, including the TB303 Bassline, TR606 Drumatix, TR808, etc. All outputs are on quarter-inch mini-jacks, apart from the 5-pin DIN socket for Sync 24, and rear panel connections are completed by In and Thru MIDI sockets.

It's in the nature of MIDI-to-CV conversion that there will always be a certain amount of 'customising' to be done to ensure that your synth responds just as you want it to; the Pro 2 has both hardware and software controls to take care of this. The hardware consists of 10 trimmer pots — five per channel — that take care of assorted calibration functions, and the software controls consist of several parameters for each channel.

We'll look at the software controls first, which are identical for the independent channels A and B. All parameters can be stored in the Pro 2's non-volatile memory, so you don't have to re-programme every time you switch it on. You can choose a MIDI channel, and any continuous control source (continuous controller, aftertouch, pitch bend, mod wheel) for Aux 1 and Aux 2, and also specify Offsets for Aux 1 and Aux 2; this is a default level, between 0 and 127, to which Aux 1 and 2 return when a Reset All Controllers message is received, or when the Pro 2 is switched on. Note Priority and Trig/Retrig let you determine how new notes affect old ones. Priority can be set to low, high, or new (new is generally best, though it can be a lot of fun to select high, then play a series of notes an octave or two up from a sustained bass note), and Trig/Retrig determines whether or not a new note will retrigger the gate when a new note comes along. Switching this off can allow for more expressive soloing, as you can play a melody in the decay and sustain segments of a sound; with each successive note, you can decide whether to trigger the attack, or 'bend' the current note to the new pitch.

The final Pro 2 parameters are Arpeggio Clock Divide, which sets the number of MIDI clocks that the Pro 2 needs to hear before sending out its next pulse from the Arp Clock output, and Continue = Start. This latter, on/off, parameter sets whether an incoming MIDI continue message will be ignored or will be treated as a start message for the Sync 24 and Arp Clock outputs.

The trimmers are all accessible via small holes in the front panel — you'll need a mini cross-head screwdriver. You can adjust CV Init (the basic CV level), to change the absolute tune of a slaved synth, and the CV Scale, to adjust relative tuning up the keyboard. The Pitchbend trimmer sets how much the CV output is modulated by MIDI pitch bend messages, and Aux 1 and Aux 2 set the range of control voltage (maximum of 4 to 14 volts) available at their respective outputs.

Internal retrofits for analogue synths have a lot to recommend them — notably the fact that you may get considerably more scope to control sound parameters in real time via MIDI — but the Pro 2 does everything you could reasonably ask of a stand-alone MIDI-to-CV convertor; the option of the Hz/V output is a welcome bonus. I found it easy to use, totally reliable, and reassuringly solid. If you're looking for a stand-alone convertor, you couldn't do better than invest in a Pro 2.

Further information

Kenton Electronics Pro 2 £176.25 inc VAT.
Pro 2/Hz (with Hz/V output) £205.63 inc VAT.

Kenton Electronics, (Contact Details).