Digital Multi-effects Processor
Article from Music Technology, April 1989
Following the success of their Midiverbs and Microverbs, Alesis have developed a unit capable of providing no less than four audio treatments simultaneously. Ian Waugh practices his four-play.
The heat is on to produce a cost-effective, programmable multi-effects processor - Alesis' history of winning budget designs makes the QuadraVerb one to watch.
ON THE OUTSIDE the QuadraVerb has two knobs to control input and output signals, four LEDs to indicate input level, a by-now-standard l6x2 LCD display, two buttons to access pages during editing, two buttons to alter values and 12 buttons to select the effects and various edit functions. These 12 buttons have central LEDs so you're never in any doubt about what you're doing.
The buttons are solid plastic and the harder you press them the faster the display scrolls. This works well for most parameters (as long as the unit is securely mounted) but altering some of the EQ settings is a real chore. For example, the Hi EQ Frequency setting in the threeband parametric (more on EQ shortly) can range from 2000-18,000Hz. That can give you a pretty sore pinky. You can go directly to any program number by holding the Prog button and pressing the other buttons (they're numbered). A similar punch-in facility would have been useful for other parameters - especially the EQ.
Inside, the QuadraVerb has a quoted frequency response of 16Hz-2OKhz and a dynamic range of 85dB. It contains a custom-designed VLSI chip with 16-bit resolution and 24-bit processing. What all this means is the effects are pretty smooth and the background noise is fairly low.
On the back are left and right audio input jacks. They're high impedance and ideally suited for use with instruments and line level signals. Although microphones can be connected directly you may get better results routing them through a mixer.
The unit is powered by an external power supply which plugs into the back. Other sockets include MIDI In and MIDI Thru, a bypass jack to bypass the effects and a program jack to let you step through a range of programs.
Whereas the Midiverbs deal in preset programs, QuadraVerb is fully programmable and you can alter virtually all the effects' parameters. The order in which the signal passes though QuadraVerb's four effects is largely determined by the Configuration. We'll get down to Configurations in a moment but first let's look at the basic effects. Sorry, basic is definitely the wrong word - the effects are comprehensive in the extreme as you will see. We'll begin with reverb.
THERE ARE FIVE Reverb types: Plate, Room, Chamber, Hall and Reverse. If you thought that creating your own reverb was simply a matter of twiddling a few knobs then think again. Alesis have really done some homework and endowed the QuadraVerb with 13 reverb parameters.
Pre-Delay delays the onset of the actual reverb, Decay determines how long the reverb takes to die away (an easy one), Diffusion controls the spaces between the reflections which make up the reverb, Density determines how quickly the reverb appears after the First Reflection and Low and High Frequency Decay help set the tonal quality and the damping effect of the environment. Between them, these should allow you to simulate just about any kind of natural environment - and artificial ones. Psychoacousticians start salivating now.
There are also four parameters which are used to create Gated Reverb - Gate On/Off, Gate Hold, Gate Release and Release level. You can gate all Reverb types except Reverse.
To make for even further flexibility (and complexity and confusion if you're not giving the QuadraVerb 100% of your attention), there are two inputs to the reverb section. Don't confuse these with external inputs; they determine from which positions in the chain the reverb takes its signals.
Input one can choose from Pre-EQ, Post-EQ, Pitch Output or Delay Mix. The first three are fairly obvious. Delay Mix, however, provides a signal which is a composite of the outputs from the Pitch and EQ sections as determined by the Delay input selection. You've really got to take that on trust until you get to the Delay section.
Input two can choose ether Pitch or Delay (no strings this time) as its source. Reverb Input Mix lets you balance
"Whereas the Midiverbs deal in preset programs, QuadraVerb is fully programmable and you can alter virtually all the effects' parameters."
the two inputs or select only one as the reverb source. Well, it's nothing if not comprehensive.
The quality of the reverb is superb. It's very difficult to attribute a character to it as you can make it bright, harsh, dull or whatever by altering the vast number of parameters. In comparison with some other effects units, however, I'd call it "warm".
THERE ARE THREE types of Delay: Ping-Pong, which bounces the signal from one side of the stereo field to the other; Stereo, which consists of two separate delays which can be individually varied; and Mono. The maximum stereo delay times are 400ms and 750ms depending upon the Configuration. The mono delay is twice as long - 800ms and I500ms.
A feedback parameter determines the number of repeats. Even on maximum the delays are crystal clear and show no sign of signal degradation. As with reverb (and, again, depending upon the Configuration) there is a choice of inputs from various positions in the signal chain.
THERE ARE SIX types of Pitch Change effect: Mono and Stereo Chorus, Mono and Stereo Flange. Phase Shifter and Detune. Those Pitch Change effects which are produced with an LFO (Low Frequency Oscillator) let you choose a triangle or square wave. There are speed, depth and feedback controls, too. Input to the Pitch section can be Pre- or Post-EQ.
Detune has a range of around plus or minus half a semitone. An octave range would have been useful for playing harmonies or just thickening sounds by adding a sub-octave but considering all the other goodies it would be churlish to gripe.
THERE ARE THREE types of EQ: three-band and five:end parametric and Il-band graphic. The type available is dependent upon the selected Configuration (coming up soon, honest).
Parametric EQ lets you "dial' the frequency which you want to alter. Mixers, for example, tend to have rotary parametric EQ controls labelled Treble, Mid and Bass.
Graphic equalisers offer a preset range of frequencies which can be cut or boost. On a hardware unit the control settings form a graph of the frequency spectrum, hence its name. On the QuadraVerb the LCD shows a frequency graph which you alter with the Value buttons. This is a neat idea although the display is only capable of showing a seven-step resolution and you have to press the value button twice to move the display one step. Cut and boost on all EQ sections is +/- 14dB.
The degree of control offered by the EQ section is nothing short of amazing; it's better than some dedicated EQ units. Someone once said you can't have too many equalisers in your studio and that's probably true.
OK, NOW WE'LL look at Configurations. These are really the heart of the QuadraVerb's operation. Five Configurations determine the order in which the effects are placed in the audio chain. The signal generally passes through the effects in series, although input can sometimes be selected from an effect earlier in the chain or from a mix of two outputs - as you'll recall from our look at the reverb section.
The first Configuration is known as QuadMode and allows all four effects to be used simultaneously in this order: Three-band EQ>Pitch >Delay> Reverb. This is the most sophisticated of the Configurations and the number of possible arrangements of effects must be legion.
The second Configuration makes special use of pitch and EQ to produce a Leslie effect: Leslie>DI>Reverb. It simulates the famous Leslie speaker sound without which no Hammond organ is complete. It gives you control over the stereo separation and the motor speed (off, slow or fast). You can also cut or boost the level of the upper horns.
It's quite difficult to simulate a Leslie electronically (as organ manufacturers know), but the QuadraVerb does the job incredibly well. In fact, this was one of my favourite effects. By adding just a splash of reverb it turned a flat and uninteresting DX organ into a sound I'm sure Jimmy Smith would have been happy to play. When you alter the speed you can hear the rotors speed up or slow down - not unprecedented but in my book, absolutely brilliant.
The third mode has this arrangement: 11-band Graphic EQ> Delay. The bands range from 16Hz-16KHz.
The fourth Configuration is Five-band EQ>Pitch> Delay. No reverb on this one which is rather a shame - it's amazing how quickly you miss it when it's not there. The manual suggests it's a good setting for guitarists - or indeed anyone who needs extra EQ facilities.
The final Configuration is Three-band EQ>Reverb. Use this if reverb is the primary effect you require. Although not shown on the Configuration display, stereo chorus is also available via the Pitch control. The Reverb types here are different to the others (they have the suffix 2 instead of 1) and have a slightly different tone.
"Mix Edit lets you mix together not only the direct and treated signals but it also lets you program the output levels of the individual effects."
Alesis are keen to point out that there is no deterioration in the signal no matter how the effects are arranged - and my ears would be hard pressed to disagree. However, if you crank the unit up you can hear whispers of noise as you flick through the settings. Heavy reverb, flanging and some pitch effects are the worst culprits, but if you're sensible about levels there is little that would cause any problems.
THAT'S A FAIRLY impressive list of functions but hang about, 'cause there's more. The QuadraVerb lets you alter effects parameters in real time via MIDI. This is something of a rarity in effects units, but it's likely to become increasingly popular (and it's one reason for the quick release of ART's Multi Verb II).
The QuadraVerb lets you control up to eight parameters simultaneously using from one to eight MIDI controllers. These include pitch-bend and modulation wheels, aftertouch, a note on command (but you can't specify which note), note velocity or any one of the 28 MIDI controllers.
A total of 50 parameters can be controlled in this way, although their availability is determined by the Configuration. Most of the reverb, delay and EQ parameters are controllable and you can alter the Leslie parameters, too, which means you can set up a controller to switch between chorale and tremolo speaker effects (yep, I really do like this one).
Got a digital synth? Assign the EQ to a pitch-bend wheel for instant filter sweeps. Or assign velocity to EQ to make a sound brighter or more dull depending upon how hard you play. You have to be careful here, however, as quick severe alterations can cause a few clicks.
If you're really into creative processing, how about setting up a few control tracks on your sequencer to modulate these parameters?
And talking of MIDI, the QuadraVerb can be set to Omni mode or it can transmit and receive on any MIDI channel. With Program Change On, it responds to patch change information by selecting the corresponding program number. For example, sending patch change 10 will select program 10. In Table mode, incoming patch numbers can be assigned to any program number. The MIDI functions are global and are not stored with individual programs.
You can toggle the MIDI Thru socket between Out and Thru functions and you can dump any or all of the programs via a System Exclusive MIDI data dump - very handy indeed if your sequencer supports this.
The QuadraVerb has 100 program memories and 90 are filled with factory settings. You can overwrite all of these with programs of your own but you can recall the factory settings at any time as they are also stored in ROM. 100 memories may seem generous but the range of effects available made me wish for 100 more.
One of the first things I noticed about the Quadra Verb - apart from its sleek lines and its handsome, debonair, man-about-town exterior - was its lack of a Mix control to adjust the balance between the direct and treated signal levels. Instead, a separate mix is produced for each program using the Mix Edit function. This lets you mix together not only the direct and treated signals but it also lets you program the output levels of the individual effects.
It's far more versatile than any simple wet/dry control could be, although I still reckon an external control would be useful.
The Bypass button (and Bypass Jack) bypasses the QuadraVerb's effects and channels the Direct Signal Level to the outputs. If the Direct Signal Level is set to zero in the mix (as it is in the Leslie programs) you won't hear anything. I can see the logic behind this but I think I'd rather be able to hear what the complete original signal sounds like. Still, it's no big deal.
The manual is reasonably helpful and full of diagrams of the LCD, although its style is rather stilted. It explains the reverb parameters and EQ sections very well although a short tutorial section would not go amiss.
WHILE THE QUADRAVERB is not difficult to program once you've assimilated the manual - it does bring a certain amount of multiple-button pushing to the effects processor. I wonder if it would be possible to write an editing program for it.
Although it's not too difficult to work out what most of the preset programs are about (use your ears), a description of their construction and some applications would have been really useful. And what about a reference card like that supplied with the Midiverb II? It could contain a list of the factory presets with a space next to them in which to write any new programs of your own.
The QuadraVerb is just crying out for an applications book, too. Yamaha produce one for the REX50 and two for the SPX90 - and they're free! Not all musicians are well-versed in the gentle art of psychoacoustics and such a book, I'm sure, would prove invaluable and greatly enhance the usefulness of the unit.
Any niggles about the QuadraVerb are of a decidedly minor nature. Make no mistake: this is a goody.
At a RRP only £20 more than the price at which the Midiverb II originally hit the streets, the QuadraVerb continues Alesis' "more sounds for your pounds" policy (if that's not their policy it ought to be). It's an excellent piece of equipment, well worth the readies and it will prove irresistible to home recording enthusiasts and studios alike. Now, where's my cheque book?
Price £449 including VAT.
Review by Ian Waugh
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