Programmable MIDI Reverb
In the first of two appraisals of digital reverb units that offer real-time control of parameters via MIDI, Rick Davies analyses Korg's affordable approach...
There was a time when the only thing MIDI allowed you to do on a signal-processor was change programs. But now all that is changing — and fast.
AS WITH SYNTHESISERS, digital reverb units are going through a visible evolution as MIDI makes its way into the hands of an ever-increasing number of musicians and engineers. But perhaps most surprising is the sophistication of MIDI implementations in digital signal processors, which have benefited from as many innovations as keyboards have.
Starting with programmability, the logical first step was to make program changes possible over MIDI, followed quickly by assignable program changes by which one incoming program number could select another program number, as the user's circumstances demanded. This last point was very encouraging, since there has never been any guarantee that program 23 on a given synthesiser will sound good with program 23 on a MIDI-equipped reverb. Then there's the matter of the organisation of programs: some instruments organise programs in banks of eight, others in banks of ten; some starting at 00, others at 11, and so on. And then you have to bear in mind that some keyboards (notably the Casio CZ101) have a limited number of programs, which could be less than the number of reverb programs available - hence some reverb programs won't be accessible over MIDI at all.
The last year has seen many developments on the keyboard market in the area of MIDI controllers and System Exclusive dumps; new types of controllers, computer-based and stand-alone, generic System Exclusive patches or sequence filers, with other new angles on the way. It was only a matter of time before these made their way into signal processors.
Perhaps this is why the DRV2000, one of Korg's latest digital signal-processors, may not come as that much of a surprise, though it only takes a look beneath the superficial layer of its specification to see a gem of a reverb at what seems to be a reasonable price. Still, the market's always in gear and going new places, so the question before us is, "does the DRV2000 go where the rest of the market is going?"
HOUSED IN A 1U-high, 19" rack-mount chassis, the DRV2000 offers a selection of 96 programmed effects settings, 80 of which are user-programmable. Korg provide 16 basic reverb, delay, and combination effects as starting points, each with its own set of adjustable parameters, leaving the user with plenty of programming options without requiring a thorough understanding of reverb to get useful results. These basic programs are permanently stored in program numbers 1 through 16, and cover an assortment of hall, room, plate, and gated reverbs, stereo delay programs including flanging, chorus, and pan effects, and combinations of reverb and delay effects. These programs provide between four and ten adjustable parameters for the user, and the manual goes into a suitable level of detail to guide the first-time programmer through each program's parameters.
The DRV2000 is a mono in/stereo out machine employing 16-bit digital processing (which provides a respectable sound quality - something which is becoming more common lately). The unit relies on just a handful of front panel controls to access all of its functions, but Korg have done an admirable job in taking advantage of MIDI to make life considerably easier in almost every respect - from program selections to real-time parameter control.
This is not to say that Korg have cut corners where they couldn't afford to: ¼" phone sockets are provided for the audio input and outputs, and a Gain switch on the rear panel selects either +4dB or -20dB signal levels, while the front panel Input control and its corresponding LED bar graph help avoid overdriving the input. The Mix control performs the usual duty of setting the dry/effect blend.
Like many other budget signal processors, the DRV2000 relies on serial access for program selection, having no numeric keypad or set of dedicated program select switches. This means a fair amount of time spent scrolling through the programs to get from one program to another at first, but once you've had a chance to hook the DRV2000 to a MIDI controller, you'll find yourself spending less time working the DRV's front panel controls, and more time operating it from the controller.
A large LED display shows the selected program number, while a back-lit LCD shows the selected program's title along with one of its parameter values. For example, a "vocal plate" program might display the reverb time value, whereas a "gated reverb" program might display the predelay value. This flexibility is particularly useful in situations where quick edits are required; after working with the DRV for only a short while, it becomes apparent which parameters are most often adjusted in the different types of effects.
"If you happen to have a keyboard with assignable MIDI controllers, it would be easy to customise the DRV so that each program's main parameters could be adjusted without ever coming near the unit."
The 16 different basic programs allow for a good variety of effects, including reversed gated reverbs, ping-ponging stereo echoes, stereo chorus, and dynamic panning. In the latter category, the DRV offers some variety to stereo imaging by producing left-to-right and right-to-left continuous panning with variable "phase" for control over the apparent depth of motion. This effect is most dramatic when heard without the dry signal, so the DRV's bandwidth limitations (20-12kHz) are unfortunately more noticeable with this program than with the reverb programs, for which this bandwidth is quite acceptable. For this reason the DRV is probably best suited for use as an auxiliary effect, a situation which would also allow independent equalisation of the dry and effect signals.
THE DRV OFFERS the type of control format that has become standard on most budget synthesisers and signal processors. The controls include several mode switches (Program, Parameter, and Utility), a Write switch for storing edited programs, and increment and decrement switches for stepping through programs, parameters, or values, depending on the selected mode. As mentioned earlier, the specific parameters available for editing depend on the current program's type of effect. For example, a stereo chorus program has fewer parameters to control than, say, a reverb/echo combination program.
It would be easy to get by with these basic programming functions, editing one or two parameters, changing the program title, and writing the new program to other program locations, but the more adventurous programmer won't be able to ignore the multi-modulation feature offered for external MIDI control. Each effect type has certain parameters which may be adjusted under MIDI control, but the choice of specific controller affecting each parameter is left up to you, and can vary from one program to the next.
In fact, each program can have any combination of two eligible parameters controlled by any two of 70 possible MIDI control sources - hence the "multi-modulation" tag.
Possible modulation sources include MIDI key numbers, key velocity, aftertouch, pitch-bend, and any of 64 continuous controllers.
Needless to say, if you happen to have a keyboard with assignable MIDI controllers, it would be easy to customise the DRV's programs so that each program's main parameters could be adjusted without ever coming near the DRV, which could then rest undisturbed in a rack off to the side somewhere.
To test this feature, I used a Yamaha DX7IIFD, assigning its two sliders (CS1 and CS2) to continuous controllers 11 and 12. I then programmed the DRV2000's "Comet" program (a reverb/chorus combination) to assign controllers 11 and 12 to the reverb time and chorus modulation amount respectively. The DRV's multi-modulation section lets you establish positive or negative modulation amounts for each source individually, so there's no need to adjust any of the program's other parameters to accommodate the controller range. This proved to be quite effective; while playing the DX through the DRV, one slider set the length of the tail of the reverb, while the other slider controlled the depth of chorus applied to the reverb. The only problem I came across was that a few of the parameters which the manual indicates can be multi-modulated could not. Being a synthesist, I'd prefer it if everything could be modulated by everything else, but that's not to say that I lost any sleep over this temporary setback; on the whole, this is a very clever implementation.
"The DRV can be set to interpret MIDI note numbers as program selectors - interesting, but I'm not sure how you'd go about playing the controller without selecting a different DRV program with each note."
Now all that's needed is a way of calling up DRV2000 programs corresponding to programs on a MIDI master keyboard (or other controller) without having to juggle programs around inside either the DRV or the controller. Some keyboards already incorporate features for this very application, and there are even stand-alone devices, such as the Voyce LX4 and LX9, which essentially enable simpler controllers to have similar control. But the DRV2000 also has this power. Using the Utilities switch, you can access a "switch program change" display. From there you simply enter an incoming program change number, followed by the number of the program you want it to select on the DRV when it is received. Simple, elegantly implemented, and the sort of thing that should, in a perfect world, cause other manufacturers to follow suit. Mind you, on the last point, things could get confusing if every piece of MIDI equipment had different program-change assignments going on at the same time.
In fact, this brings up an odd detail which I stumbled across just before testing the DRV's System Exclusive dump feature: the unit transmits a program change whenever it receives one at its MIDI input. While this might be useful for passing along program selections to other instruments in a MIDI chain, this is usually what MIDI Thru sockets are for. I had the keyboard and DRV2000 in a closed loop, and after selecting program 13 on the keyboard, the DRV changed to program 96 (as it had been programmed to). But this caused the DRV to transmit another program change which, in turn, changed the program on the keyboard! Although I'm willing to avoid running the DRV's MIDI output into other instruments to prevent this from happening, such evasive action shouldn't be necessary. After all, the DRV's MIDI output can be switched to operate as a MIDI Thru at any time.
On the subject of MIDI program selections, the DRV can also be set to interpret MIDI note numbers as program selectors. Now, while this is very interesting, I'm not sure how anyone would go about playing the controller without selecting a different DRV program with each note. There is an Enable/Disable toggle, but since this feature is intended for remote control, I remain unconvinced that dedicating one keyboard to program changes is a viable alternative to conventional program selections from instruments' front panels, especially given the DRV's rather slick features in that department.
However, considering how the MIDI keyboard controller is becoming standard fare these days, Korg's general approach to central control over effects from musical instruments should earn them a few points with musicians in both live and studio environments. After working with the DRV for a while, I wondered how soon it will be before MIDI effects controllers become as popular as keyboard controllers. The Voyce LX4 and LX9 do fine for program selections and MIDI mapping, but as far as MIDI continuous controllers are concerned, the Yamaha MCS2 is the only device which springs to mind...
The DRV can store its programs over MIDI using a System Exclusive dump. If you don't happen to have a SysEx program for the Atari ST or another generic program librarian (and let's face it, most UK musicians don't), Korg recommend using their MEX8000 Memory Expander. If you don't have access to either of these, despair not: first of all, the DRV's program memory is non-volatile (naturally), so it remains intact after switching power off; second, program variables are so few, it really wouldn't take too long to keep hard copies (you remember pieces of paper, don't you?) of parameter values for custom programs.
The DRV2000 dedicates its attention to reverb and delay effects, and performs well. The factory programs are a good selection and, thanks to Korg's clever MIDI implementation, you couldn't ask for a better way of reaching them.
Price £499 including VAT
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Review by Rick Davies
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