QuadraVerb: an Early Review

Date: (around February 1989) Posted to rec.music.synth, I think.

My long-awaited QuadraVerb showed up over the weekend. Here's some initial impressions, I only played with it for a few hours. I don't work for Alesis, etc, I'm just a regular guy. Feel free to repost this elsewhere if you feel it's worthwhile, but don't take what I say for granted -- I might be wrong. Finally, my dealer said he didn't think he'd see more units for about a month.

Executive Summary: Fantastic. Alesis has done it again.

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I'm not sure where to start. OK, how about an overview:

The Alesis QuadraVerb is a 16Hz-20kHz bandwidth stereo programmable effects box with four digital effects (EQ, Pitch Change, Delay, Reverb). The effects can be used in parallel or in serial (or a combination). Specs say the dynamic range is 85dB, less than .1% distortion. Processor speed is 24 MIPS (no Z80 in this baby!). Conversion scheme is 16-bit linear PCM. It's fully MIDI-fied.

In the following description, 'program' could mean 'patch'. I would say 'effect' but there are multiple effects in a program...

Some features:

Touch sensitive (multi-speed!) programming buttons. Many have integral LED so you know what mode you're in. If you press harder you move the parameter faster.
2x16 character LCD display.
Stores 100 programs. Comes with 90 (in ROM) that you can overlay into the RAM. At any time you can recall one or all the ROM programs into RAM.
Real-time control of 8 simultaneous parameters via MIDI (you pick the controller type and the parameter it controls).
All functions, parameters and volume levels are programmable per program.
Stereo In/Out (via four 1/4 inch jacks).
Effect bypass jack on the back (as well as a button on the front).
You can name your programs (up to 14 characters).

Initial observations:

The QuadraVerb comes in a 1U rack mount enclosure, about 5" deep. It's a metal case, painted black. Phillips screws hold the case together.
The power supply is detached from the unit, so it's one of those 'transformer on the wall' kind. Reduces noise and hum maybe, but it's a pain too. It's bigger than the HR-16/MMT-8 power supply.
Alesis doesn't supply audio cords with the unit, so you'll need to pick up four if you want to do stereo in/out.
I picked up the unit and there was a rattle. It sounded like something heavy, not like a piece of paper. Opening the case showed a spare screw and nut. I looked hard but could not determine where these should have gone, so I removed them. (that's a hell of a way to pack spares :-) I checked to make sure nothing was scratched or otherwise messed up by the bouncing parts. Everything looked OK. [note: if Alesis says this voids my warranty, think of how much more it would have cost them had I plugged it in [under warranty] while the nut shorted three pins on an IC]
The ROM was under an RF shield (at least I think it was an RF shield, but it was only a flat piece of unpainted metal, no sides at all). There was a sticker that said '15-JAN-89' on it. I forgot to check to see if the ROM was socketed.
The PC board had several (about six) 'goofs' where jumps had to be made by hand, including some piggybacked resistors and the like. Generally the PCB looked clean. Mine was labelled Rev C.
The user manual is 68 pages, and not too bad. You really should leave your studio and read it (the manual) fast once, then go back to the studio and read the Theory section again while you play with the unit. I would have presented the material differently, but I'm picking nits. If you've suffered with most manuals for musical equipment, you'll love this one. My manual came with a one-page insert that covers two items not covered in the manual.
The front panel is clean (well laid out) and easy to use.
85 of the 90 ROM programs are 'musical' unlike some programs you get from many vendors. The last 5 are 'demo' programs so you can hear differences between five 'configurations' (explained later).
Parameters can be varied over a generous range. Delay times can be specified in 1ms increments for example, percentages are by 1%. The input mix levels are between -100 and +100 in steps of 1, etc.
There is a footswitch jack on the back to step through programs, and a range parameter you can adjust. You could use it to step through programs 50-62 for example, or backwards through 28-14.
While editing programs, you can flip between the 'original' and the edited versions of the program, to compare the two, without having to store the 'edited' version first.
At any time, pressing the two value buttons (up and down) together sets the parameter to a 'default' value.

Here's the basic signal diagram:

	dry signal --> EQ  --> Pitch --> Delay --> Reverb --> output

I'm not going to draw in all the possible signal routes, so I'll tell you: Each output can be routed to just about any input. For Pitch input, you can select either Pre- or Post-EQ. Any amount of Pitch output can be fed back into its input. For Delay input, you can select select either Pre- or Post-EQ, and mix it with as much or as little of the Pitch output as you want. Any amount of Delay output can be fed back into its input. There are two Reverb inputs: One is switchable: Pre-EQ, Post-EQ, Post-Pitch or Pre-Delay (the Pre-Delay is after the Delay Mix). The second Reverb input is either the Post-Delay or the Post-Pitch. These two inputs can be mixed before being sent to the reverb.

The unit has five preset 'Configurations' which are variations on the above theme. They are:

Config 1: QuadMode(tm): 3-bandEQ->Pitch->Delay->Reverb
Config 2: Leslie->Delay->Reverb
Config 3: GraphicEQ->Delay
Config 4: 5-bandEQ->Pitch->Delay
Config 5: 5-bandEQ->Reverb

You don't really need to grok configurations to understand the rest of this description, and these five configurations don't make the QuadraVerb as limited as it might look at first glance.

Each effect is impressive by itself. All are full bandwidth. A rundown:

EQ - Usually an (almost) three-band parametric. The low and high bands are modified shelf-type EQs (you can't adjust the bandwidth, just the frequency) while the mid-band EQ is truly parametric (bandwidth adjustable from .2 to 2.55 octaves). Everything is +/-14db.

You can also get a five-band parametric. In config 4, you lose the Reverb but almost double the Delay time. In config 5 you lose the Delay but you can still get a chorus out of the Pitch section. Again, the low and high bands don't have bandwidth controls, but the middle three do. All are frequency adjustable, like the 3-band EQ.

You can also get an 11-band graphic EQ with delay (you lose Pitch and Reverb, however, the delay time is just about doubled from 'normal' operation). The EQ really is graphic! They use 11 line segments that can each move up and down on the LCD.

PITCH - The pitch can be either a Mono/Stereo Chorus, Mono/Stereo Flange, Pitch Detune or a Phase Shifter. You can vary the depth, speed and waveshape (triangle or square) of the LFO. The waveshape is only available in Chorus mode. You can also adjust the feedback, except in detune mode. It is possible to retrigger the flange at every new input signal event; good for drums and other percussive input sources.

DELAY - Usually 800ms delay in mono. In stereo, it's 400ms each channel. If you use the 5-band or graphic EQ you get 1500ms/750ms mono/stereo. There's also a ping-pong delay, where the delay bounces between the left and right channels.

REVERB - In addition to the two mixed inputs I already discussed, you can set and mix the amount of pre-delay - you can hear some of the reverb before the loudest part of the reverb. You can also adjust the decay time, as well as the separate controls for the low and high frequency decay (for shaping the reverb envelope). There are controls for adjusting the reverb diffusion and density (the manual has some nice graphs to show what these do). Finally, you can have the reverb gated and adjust the gate's hold rate, release rate and release level.

LESLIE - a Leslie simulator is built in. If you use it, you lose EQ and pitch controls, but keep delay and reverb. You can control stereo separation, motor control (on/off), speed (slow/fast), and the level of the high rotor in case you want the treble a little louder/softer than the bass. If you shut the motor off, the Leslie slows down until it stops!

MIX - each effect has its own level control, and there are Effects & Direct (dry) level controls, all programmable from 0-99, per program. This is in addition to the potentiometer on the front panel, which is not programmable.

MODULATION - as I said before, you can control just about everything via real-time MIDI controllers. Up to eight params can be controlled per program. For example, you can control LFO depth via aftertouch, Reverb High Decay via pitch bend, Mid EQ Bandwidth via note number, Leslie speed by an on/off switch, etc. You get the idea.

MIDI - you can assign channel (1-16 or omni, in omni mode it transmits on channel 1), turn program change on/off, SysEx on/off, start bulk or individual dump, etc. The usual stuff. In addition it has a program table, so you can map any of the 128 possible MIDI program numbers to any of the 100 available programs. Possible use would be to leave 0-99 alone and map 100-127 to various programs.

There are MIDI IN and MIDI THRU jacks. If you disable the MIDI THRU jack, it acts as a MIDI OUT only. Like the HR-16, The MIDI THRU never passes SysEx info.

And the sound? Wondferful. Clean. Relatively free of digital aliasing. Studio quality stuff here, folks.

Some minor complaints or wishes:

The user manual doesn't have the SysEx programming info, nor the bulk data dump format.
the LCD display is meant to be looked at at eye level or below. It just so happens that when sitting at my computer, I have the unit above my eye level. I can still see the characters, but they're not as defined. For most folks this will not be a problem.
I wish I could pass SysEx info through the MIDI THRU.
I'd like to be able to use the program advance table to point to the MIDI program table, rather than the 'hard' program numbers.
I'd like to be able to have control over what MIDI channel each real-time modulator listens to.

Finally, I saw no reason ten mode buttons were also numbered 0-9 in addition to their regular functions. I discovered that by holding the PROGRAM button in you can select the program number by direct entry. Much better than stepping through! I couldn't find this in the manual; maybe they took it for granted that people would know?

Anyway, I'm glad I waited. I already love this unit. The sound is fantastic. This thing is as versatile as a synthesizer, and it's one of those units you have to 'get to know' to exploit the power beyond the factory programs.

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