Kenton Electronics Pro 4

To get the most out of your pre‑MIDI synths, you need to bring them into the MIDI age. Kenton's long‑awaited Pro 4 provides a host of interfacing possibilities and is capable of controlling up to an astounding 10 different devices simultaneously. Derek Johnson connects up.

For better or worse, vapourware is a fact of life in the musical instrument industry: notable recent examples include the Waldorf Wave and Oberheim OBMx, both of which have taken years to go from concept to production. You could add to the list Kenton's rack‑mounting Pro 4 multi‑channel MIDI‑CV interface. This product has been in development since the company's original Pro 2 two‑channel MIDI‑CV interface (reviewed SOS August 1992) was launched.

But to be fair to Kenton, they have spent a lot of time making sure that what is actually implemented on the Pro 4 is what musicians want. Originally, the new interface was simply going to be two Pro 2s in a box — an attractive concept in itself. However, the company kept tabs on their feedback from Pro 2 customers and found that it wasn't too much trouble to implement some of the more popular suggestions. This attention to detail and customer requirements has resulted in the delay in releasing this unit — and let's say right away that it certainly has been worth the wait.

Panel Games

The front panel of the Pro 4 isn't as cryptic as the Pro 2's. Editing is undertaken through the use of four buttons, a data entry knob and a two‑line by 20‑character backlit LCD. The Pro 2, with its row of LEDs and two‑digit LED display, was never that difficult to programme, but the Pro 4's LCD makes light work of customising the new machine. Activity LEDs are provided for the four main MIDI‑CV channels (labelled A, B, C and D), MIDI data input and MIDI clock. As with the Pro 2, each MIDI‑CV channel is provided with mini pots, accessible through holes in the front panel, for adjusting the tuning and octave scaling of the Pro 4 to your synths.

Inside Story

The most important point to understand when operating the Pro 4 is that, although it is nominally a 4‑channel interface, it actually offers far more than this: it's divided into eight independent sections, labelled A to H, each individually addressable on separate MIDI channels. Yes, you read that correctly: four MIDI‑CV channels, plus four 'special' channels — more on these later. The Pro 4 also provides a Sync 24 output, a programmable sync socket, eight auxiliary CV outputs and four programmable LFOs. Let's run through the facilities.

• Channels A‑D, the basic MIDI/CV channels, offer:

1. A control voltage output: this is based on the common Volts per octave pitch scaling system — it will work out of the box with your SH101, Moog Rogue, Sequential Pro 1, and so on. If you need to control synths working on the Hertz per Volt principle (Korg MS20 and Yamaha CS40M, for example), then you will need the optional Hz/V board. Adding this board is simply a matter of removing the lid and plugging it in. Contact Kenton for details; it will cost around £80, but offers four Hz/V outputs.

2. A +15V gate (or trigger) socket.

3. An additional Trigger out socket, providing seven further trigger/gate options; which you use depends on your synth. The options are: three varieties of S‑trigger (used by Moog, Korg and Yamaha CS‑series synths), three varieties of V‑trigger (could be used to trigger EGs, for example on the ARP 2600, or to trigger analogue drum modules or sequencers).

Each channel also features portamento functions, pitchbend range, transpose value and LFO parameters.

• Channel E: Wasp port.

Controls an EDP Wasp or Gnat synth; limitations of the Wasp mean that it only responds to a three‑octave range and doesn't recognise pitch bend or any controllers except sustain pedal.

• Channel F: MIDI channel filter.

This is not strictly a MIDI‑to‑antique‑synth channel. It allows you to re‑channelise data on one MIDI channel to any other, which is sent via the Pro 4's MIDI Out (but not the Thru). This allows keyboards with primitive MIDI specs to transmit on any MIDI channel (great for Yamaha's DX7, for example, which can normally only transmit on channel 1) or to receive on just one MIDI channel (could be used with Roland's Jupiter 6, which is normally always in Omni mode).

• Channel G: DCB port.

Roland's Digital Communications Bus (DCB) was a pre‑MIDI polyphonic digital communication protocol that appeared on a few instruments (the Juno 60 and some late Jupiter 8s, for example). Only notes are transmitted, although Jupiter 8s will respond to programme changes.

• Channel H: KADI port.

The KADI (Kenton Auxiliary Digital Interface) can at present be used to trigger individual sounds on a Kenton‑modified Roland TR808 or TR606. You'll also need the correct lead. This port should be the focus of future options.

Also available are eight auxiliary control voltage outputs. Each CV can be controlled from virtually any MIDI controller — pitchbend, velocity, aftertouch and controllers 1‑120 — and all are freely assignable. For example, all eight could be assigned to one CV/Gate channel, or each CV/Gate channel could have two auxiliary CVs each. Providing your synth has the right inputs (labelled VCF In, VCF fcM, Filter Ext In and so on), velocity or aftertouch could be used to alter a synth's filter cutoff in real time. Given the right connections, these extra CVs offer unprecedented MIDI control over your analogue gear.

The extensive control facilities don't end there: Kenton have provided the Pro 4 with four independent, assignable, MIDI‑clockable LFOs. Each LFO has its own speed, waveform and MIDI clock sync value. LFO Waveforms available include triangle, sawtooth up and down, square, pulse 10%, 20%, 30% or 40% and sample & hold. I could complain that the pulse width isn't fully variable, but that would be churlish, wouldn't it? The LFOs can be assigned to the four CV channels and/or auxiliary outputs 1‑4, and add a fluctuation to the voltage, resulting in pitch variations when used with a control voltage routed to pitch, or timbral variations when an auxiliary CV is routed to a filter cutoff input. This is an unexpected and unique facility that adds to the general usefulness of the Pro 4. Which other MIDI‑CV interfaces actually add to the sonic capabilities of the connected synths?

I wouldn't expect you to be surprised if I told you that there are still more facilities. A Sync 24 DIN socket, for driving Roland MC4s, TB303s, TR808s and the like, is at the rear, as is a programmable clock pulse output. This provides a +5V clock pulse for clocking arpeggiators and some sequencers and drum machines; it can transmit any value between a quarter note and a 32nd note triplet. The only option missing here is the 48ppqn DIN sync used by Korg on just a few instruments — the DDM110 and DDM220 drum machines, for example. This could, however, be upgraded in software if there was demand.

Connectors

The Pro 4 is one of those rare devices where the back panel is as interesting as the front. Nearly all connections are on mini‑jacks (20 in all); there are also MIDI In, Out and Thru sockets, the Sync 24 DIN socket, and a pair of 15‑pin D‑type sockets that provide the outputs for the Wasp/DCB and KADI channels. The only other connector is a three‑pin mains socket for the internal PSU.

To be honest, mini‑jacks are a bit of a pain, but I can see that using quarter‑inch jack sockets would have added to the unit's cost, as well as making it more untidy and crowded at the rear. However, once it's plumbed in, the fiddliness of mini‑jacks ceases to be an issue — some users may like to wire up a dedicated patchbay.

How It Works

Programming the Pro 4 couldn't be easier: to select a parameter, press the Parameter button, and scroll through the options with the data entry knob. Parameter values are altered by pressing the Value button, and using the knob to change the value. Simple. The only irritation for some may be the large number of parameters that have to be scrolled through, although the superior‑quality stepped data knob makes this easier. The other two buttons on the front panel store and recall user settings, internally and over MIDI.

There are actually eight user settings (memories) in all; that may not seem like a lot, but in the average situation the various parameters will be set up once only. Those with more complicated, modular synth systems may require a little more flexibility and want to do more repatching. If this minority finds eight memories to be restricting, it's easy enough to do a system exclusive dump of the Pro 4's memory contents over MIDI. In addition, the Pro 4 has a comprehensive MIDI spec, and the SysEx info sheet supplied provides all the data required for setting up a profile in a generic editor, in order to control the unit externally.

Conclusions

I found the Pro 4 a doddle to use — the data knob and clear LCD make for straightforward programming. The calibration pots were a bit fiddly for me, but the Pro 4 probably isn't going to be recalibrated every day. If you use a Wasp and a DCB‑equipped synth, you'll need to shell out for a splitter lead (both channels share a socket due to space considerations), and Hz/V‑equipped synth users will need the optional board, but that's about the limit of my operational complaints.

I don't have a Wasp or a DCB‑equipped synth, so I couldn't test out every corner of the Pro 4. I could, however, have it chucking out notes on two channels along with Sync 24 and an arpeggiator clock; it didn't fall over, and added no discernible delays. Even though the machine we reviewed was a beta test model, I had no problems. Pre‑production models often have incomplete software or bugs and the like, but not the Pro 4. Everything worked as expected, and the only major change to software in the production units should be the implementation of a poly mode for the four CV outputs — ideal for users of Oberheim's aged 4‑voice synth.

It's hard to fault the Pro 4: the flexibility and stability of the final product is testament to the thought that has gone into development. Pre‑MIDI synths are still enormously popular, which virtually assures the market for the Pro 4. Had it simply been a four‑channel MIDI to CV/Gate convertor, it would have offered good, if not stunning value. In actuality, it is a really excellent buy: Kenton have gone overboard on facilities, some of which simply aren't available elsewhere. The Pro 4 can control up to eight synths directly, on separate MIDI channels, as well as synchronising a further two drum machines or sequencers to MIDI. Beat that for under £450 — it works out at less than £45 an instrument. A wide range of triggering options, auxiliary CVs and four LFOs make Kenton's Pro 4 a virtually unmissable piece of hardware — only certain MIDI internal retrofits would come anywhere near the facilities on offer here, and that could be rather an expensive alternative. If you have more than a couple of vintage synths or drum machines, and want to interface with the MIDI '90s, then you can't afford to be without a Pro 4.