Doepfer Drehbank

There are now quite a few MIDI control surfaces on the market, yet the knob‑laden Drehbank, which offers interesting possibilities for interconnection between vintage CV synths and modern MIDI gear, is sure to excite much interest. Paul Nagle turns on and tunes in.

Just over a year ago, when reviewing the Clavia Nord Modular synth (SOS April and May 1998), I suggested that the world (or at least my small corner of it) was now ready for a "100‑knob MIDI control box". It seems that the genie who serves German synth company Doepfer was listening that day. He was in a good mood too, because my wish has been granted — well, almost. The Drehbank is a compact, programmable MIDI controller that doesn't actually have 100 rotary knobs, but since the 64 it does have are effectively doubled by two onboard memory banks, it'd be churlish to complain. Incidentally, anyone offended by excessive use of the word 'knob' should stop reading right now.

The Knob Box

The German word 'drehbank' means 'turning lathe', indicating the obvious difference between its knobby surface and other, slider‑based, MIDI controllers such as Doepfer's own Regelwerk (reviewed SOS February 1999) and Peavey's PC1600X (reviewed SOS March 1999). The Drehbank's panel is a tasteful gunmetal grey, bearing knobs of pale grey plastic. These are each 10mm wide (flaring to 15mm at the base) and are closely packed together at 25mm intervals. If, like me, your fingers are the slender products of years tapping at a computer keyboard, this won't be a problem. Anyone who has a little more girth in the digit department, however, may have difficulty making fine adjustments without disturbing adjacent knobs.

The panel is laid out in four rows of 16 knobs. Next to each knob is a number and a small white square on which to write a label relevant to its function. At the left‑hand side of the unit, three small buttons with red LEDs are used to switch between the two banks of knob definitions and to transmit a snapshot of the Drehbank's current values via the MIDI Out socket. This latter facility is particularly handy if you're using the Drehbank as a synth editor and want to begin with knob positions that match the synth's settings. It took me a little time to suss out that sending a snapshot involves holding down the relevant button for about three seconds, releasing it, then pushing it again straight away. It's designed like this to prevent a snapshot being sent by accident.

The rear panel of the Drehbank is a little more interesting than I'd expected: along with the MIDI In and Out sockets and ubiquitous (and slightly wobbly) external power connector, there are no less than eight quarter‑inch jack sockets labelled 'External Inputs'. Their function is to translate incoming control voltages (such as those produced by old analogue synths) to MIDI events, and we'll look at why this might be a fun thing to do later.

There really isn't much else to say about the physical side of the Drehbank, other than that it can be used as either a desktop module or rackmounted using the supplied rack ears. When it's racked the connectors are at the top, so a blanking panel is supplied for those who'd prefer to hide the cables from view. Including the blanking panel, the Drehbank occupies a total of four 19‑inch rack spaces.

The Software

Since the Drehbank has no built‑in display, it is configured using an external editor program. This software is PC‑only and will run on Windows 3.11, Windows 95 and above. It ran with no problems on my Windows 98 system and the restriction to Windows 3.11 short file names was of little consequence. More significantly, I suspect users of other computers will feel shunned and generally grumpy, but since this software will run on practically any PC, and PCs are common, perhaps borrowing one might be an option to initially tailor the Drehbank. OK, I'm not going to convince any Mac owners with that argument...

Resident in ROM, four Factory presets may be loaded without permanently erasing either of the two user banks. This is achieved by holding down different combinations of the three buttons at power‑up, temporarily loading presets into memory. The presets provide a GM mixer, send MIDI controllers 0‑127 and take control of Steinberg's Rebirth microcomposer software or Yamaha's RM1x hardware groove sequencer.

Here I should point out that there is currently no English manual (though it's claimed that one is on the way), nor is the on‑line help for the editor software in English. Fortunately, the program is refreshingly simple to use, consisting of a graphical view of the Drehbank and all its rotary pots plus a 'library' window underneath. Drehbank presets are accessed from the File or Library menus: the former opens completed knob assignments and layouts; the latter places all the controls into a list from which you can drag items to the knob of your choice.

To edit the function of any knob, double‑click on it. A window appears, in which the user can set the type of message the knob will send, plus its range and resolution, and input a text label. To swap the position of a knob or copy it elsewhere, simply drag it with the mouse. I found this method a vast improvement on setting up either a Peavey PC1600 or Doepfer's Regelwerk.

So what kind of information can the Drehbank send? Actually, just about any MIDI message you can think of, including MIDI notes, controllers, program changes, pitch‑bend and aftertouch, MIDI Machine Control commands, lengthy system exclusive strings (if I've worked it out correctly from the manual, these may be up to 113 bytes long) and MIDI real‑time information such as MIDI clock.

Once you've defined what each knob will do, the data can be saved to disk or transmitted to the Drehbank with a click on either the Send or the Store button. Choosing the Store option means that your setup will remain in memory after power‑off. The data may also be exported as a SysEx file or as a text file. Perhaps the latter is intended as a handy way of getting the layout into a spreadsheet or labelling program?

By adding the means to generate MIDI data from external voltage sources, Doepfer offer a degree of interconnection between old and new gear which simply begs to be used creatively.

A particularly nice feature of the editor is its implementation of 'Table' files. These are essentially text files created for a specific device, containing actual MIDI data and a description of what it does. Thus, when I created an editor for my Waldorf Pulse synth, I began with a Table file listing all the synth's functions, copied straight from the manual (which just happens to be available on‑line). With an embarassing lack of effort, I then allocated each Drehbank knob using familiar names (Cutoff, Noise Level, Oscillator 3 Waveform, and so on) and the job was done. I discovered a few handy tricks, such as dividing the Pulse's tuning into octaves (by 'quantising' the semitone knobs to steps of 12), and was able to limit the range of the Pulse's modulation sources to just those options I use most. However, some aspects of the Pulse's facilities didn't translate that well to rotary control — particularly any kind of selector or on/off event. I feel a notched control to switch, for example, between oscillator waveforms or modulation sources will always be superior to a knob. Similarly, it seems unnatural to use a knob as an on/off switch, especially when 99 percent of its travel sets the 'on' status and only a full rotation to the right sets it to 'off'. I noticed that transmission of values was slightly uneven: the mid‑point of the data being transmitted did not quite correspond to the mid‑point of the knob's travel. Perhaps when the English manual appears it will explain whether knobs can be recalibrated, although it seems unlikely.

Other Editor facilities include Bank Copy and Initialise, plus the management of a MIDI merge function where incoming data is combined with the data generated by the onboard controls. The Options menu sets which types of incoming events are passed through to the MIDI Out, with a choice of 'normal' MIDI events, real‑time information (MIDI clock, for example) and System Exclusive.

Voltage Control

Possibly the most exciting and unusual feature of the Drehbank is one that might not be immediately obvious. I mentioned earlier that there are eight Control Voltage inputs at the rear, which are mapped directly to the rightmost two columns of knobs. Why is this exciting? Well, those eight incoming voltages (I believe four are optimised for foot pedals) become the source for data generated by the Drehbank's knobs. A typical scenario might involve connecting the output of a modular synth's LFO and using this to sweep the filter of a MIDI synth, or to perform more bizarre actions such as generating a stream of MIDI notes based on the modular synth's envelope output. Ownerof the Doepfer Regelwerk could connect its CV outputs to the Drehbank and have the voltages translated into MIDI controllers, perhaps to perform sequenced timbral changes, as on Quasimidi's Polymorph. The possibilities are fascinating.

Conclusion

I can think of no direct competitor for the Drehbank — nothing which offers quite so many programmable controls, anyway. Inevitably, some compromises have been made: yes, the knobs are tightly packed together and yes, with no display it can be hard to make accurate adjustments with them. The editor software is currently PC‑only and because there is no English manual there may be features I have missed. That said, the Drehbank is a box full of potential — potential that requires some work to exploit. There aren't many preset templates currently available, so you might have to dig out those manuals, roll up your sleeves and devise your own.

If you need something to act as a simple MIDI mixer or to perform tweaks of filter parameters or envelopes, simpler devices are available to do the job. If, however, you have designs on building a complete synthesizer programming panel or a 16‑channel XG mixer with volume, pan, effects, and so on, the Drehbank might turn out to be just the ticket. By adding the means to generate MIDI data from external voltage sources, Doepfer offer a degree of interconnection between old and new gear which simply begs to be used creatively.

At the start of the review period, I felt the Drehbank fell into the 'quite useful' category, but as I worked with it more, I started to dream up increasingly elaborate things it could do and it's now rapidly approaching 'essential' status. As Julian Clary might have said: "Think not what you can do for 64 knobs. Think rather what 64 knobs can do for you!"