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The Design Laboratories Prologue

Article from The Mix, June 1995

MIDI-CV converter and retro synth

The Prologue MIDI to CV converter from The Design Laboratories is a cost effective way of hooking up those analogue classics. Roger Brown scans the free ads in search of history waiting to be contemporised...

I had never heard of The Design Laboratories when this little black box landed on my desk, but I've a feeling we're going to be hearing more from them. As far as I know, the Prologue and Prologue 2 are the first products from this design team, but they certainly have produced a useful tool with this pair.

The Prologue is a four channel MIDI-to-CV converter with another four channels you can program to transmit pitch bend, modulation and even Roland 24 sync. Coming in at £250, it certainly represents a bargain. For only another £100, the Prologue 2 features an analogue filter section.

First impressions

Two mini jack sockets are provided for you to send sounds into the 'Retro Synth', and send them back out and into your desk. For originality this earns TDL top marks, and if they had provided 1/4 inch jacks instead of those fiddly mini jacks, I would recommend it without reservation.

As it is, there is something a little fiddly about everything on the Prologue. Programming the unit is accomplished easily enough, via a telephone-style keypad with its half-size LED display. At first, I thought I was going to have to add it to the Prologue's cons list, but it turned out to be pretty user-friendly, and I was soon happily programming the unit without too many oaths flying about.

On power up, the LEDs flash up PROLOGUE in the display, indicating an active parameter. Usually, this is the prompt for you to start adjusting values, using the 8 and 0 buttons to increase or decrease values respectively. In this case though, we are still in the top level of the Prologue's directory structure, and we use the 7 and 9 buttons, which double as left and right cursors.

Pushing 9 once moves us over to GLOBAL controls, and if we now press Enter, indicated by a # sign, we enter the edit menu for those particular settings. Here we can set MIDI receive channels; Keying, or note priority and pitch allocation; the LEO rate; the clock rate, which can be set independently for each of the Prologue's four channels; the Glissando or 'slide' rate, and finally the number of notes allocated to each of the four processors.

The Prologue has up to 16 notes, and these may be divided between the four processors in three ways, first as four four-note processors, alternatively as two eight-note processors, or finally as one 16-note processor. You may already be thinking the Prologue is very versatile in terms of its set, and you'd be right. Its only drawback is that for some, the stripped-down controls and editing facilities might prove a little difficult to fathom. I certainly found myself referring to the manual many times during the first week the Prologue was added to my setup.

Programming up varying voltage outputs (from the last four outputs), to sync a Roland unit, certainly involved some headscratching, not to mention the nightmare of constructing a special lead to run the signal out from the Prologue's mini jack outputs to a five-pin DIN. For the enthusiast though, this is all grist to the mill, and the satisfaction of running four analogue synths and two Roland synced units far outweighs the perspiration involved.

"my only complaint was that I only had two analogue synths to hook up to the Prologue"

Back to the main menu, and the next editable parameter is for the Gate outputs. Pressing # to enter this menu, we can now set the output jacks (from 1 to 8), and their source signal (which can be a MIDI controller, a MIDI clock or one of the four Gates), and which of the four processors is to process this signal. Selecting the Destination option allows you to set the the voltage level from 0 to 5V. If you require any other voltage setting, it is necessary to return to the main menu and select the next parameter, the CV outputs.

Here, we can once again select the output jack and the source signal. In the latter case we have a wider choice, and can choose from Clock, Gate, MIDI controllers, Envelope 1, LEO, Velocity, Aftertouch, Pitch Bend and one of 4 Linear or 4 Logarithmic CVs. In the last two cases, a Linear CV denotes a volt per octave, whilst the Logarithmic CV conforms to a Volt per Hz relationship. Linear outputs may be scaled and offset within a ±12 volt range, while the Logarithmic outputs can be offset to accomodate differences in voltage offsets.

Finally, if you have a Prologue 2, the main menu contains an entry called 'Retro Synth'. Pushing the Enter button at this stage provides a flashing LED, requesting that you choose number 1-5 to enter the five sub-menus, which relate to the various filter settings available.

Funky filters

First up is the Filter Envelope. Here we can set the speed of the Attack, amount of Decay and Sustain, and the filter release time, with 0 being the fastest and 199 the slowest. The manual with the review model was a little sparse at this point, and I fumbled around in the dark, before realising a filter attack rate of 199 was the slowest attack rate. That little anomaly sorted out, the filter section proved to be extremely effective. I had a series of frozen CZ101 samples in my E-mu E-IV, which I was able to run through the Retro Synth and re-invest with life and movement.

Sub-menu 2 in the Retro Synth is for Filter Frequency, Resonance, Amount and Key Track, for that classic analogue effect. If you set your modulation wheel to one of the controllers, it is possible to use this to open and close the filter in real time, for the ultimate, sequencer-friendly analogue sweep. This facility can also be used to enter values, which is also handy for more intuitive programming.

Sub-menu 3 allows you to set one of 16 filter modes, from low-pass to high-pass, with several notched settings inbetween. From here, you also set the filters' Velocity and responsiveness to Pressure. There is an Amplitude envelope for boosting your signal, and sub-menu 4 allows you to set the Attack rate, Envelope Decay, Sustain and Release. Sub-menu 5, finally, is for setting the filters' Input Sensitivity, Amplitude Velocity and Pressure.

Being able to map your master keyboard modulation wheel to these editable parameters, allows for both real-time playing of the filter and easy editing. I found the Retro Synth to be an enjoyable added feature to the Prologue, which is worth a lot more than the £100 supplement. If I had any gripes here, it was that old chestnut of having to program up the filter section digitally, using the keypad, instead of a series of twiddle-able knobs. Discovering the mappable modulation wheel feature compensated for that, however, and the Prologue proved to be a welcome addition to my studio.


Less 'user-friendly' than Kenton's Pro2 and Pro4 MIDI-CV units, the Prologue is not for the fainthearted, and many will not like its fiddly editing, or the fact that it does require more than a little knowledge of synthesis and electronics to extract the most from it. Enthusiasts will love it, and the savings made when compared to the Pro4 are enough to go out and buy another crusty analogue synth, to hook up to one of its 4 outputs.

Aside from those horrible mini-jacks which, TDL assure me, have been replaced with 1/4 inch ones on the latest models, my only complaint was that I only had two analogue synths to hook up to the Prologue. Those extra outputs proved an irresistible temptation to add some more classics to my collection!

The essentials...

Price inc VAT: £250 (Prologue), £350 (Prologue 2)
More from: The Design Laboratories, (Contact Details)

Spec check

Inputs MIDI In
External In (Prologue 2)
Outputs CV x 8 mini-jacks
Gate x 8 mini-jacks
Sound Out (Prologue 2)
Dimensions (in mm) 292 x 14 x 50 (W x D x H)

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Publisher: The Mix - Music Maker Publications (UK), Future Publishing.

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The Mix - Jun 1995

Donated by: Colin Potter

Coverdisc: Mike Gorman

Control Room

Review by Roger Brown

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