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Yamaha SPX90

£600 (almost) buys you this boxful of MIDI-controlled digital effects processors. But can they be good quality? Ian Gilby dragged himself out of the studio long enough to give us his opinions.

If you've read the advanced spec, you might well be thinking that the SPX90 packs the same sonic power as a whole rackful of effects. Well does it? Ian Gilby took it into the studio to find out.

Bearing in mind Yamaha's past achievements, their 'milestones in music technology' slogan seems so appropriate - they've proved it time and again with products like the CP70 electric grand, DX7, CX5, R1000 and REV-7 digital reverbs (though sometimes the milestone is too many miles ahead of its market - the now extinct D1500 MIDI-controlled delay being a case in point!).

Well prepare yourself for another milestone in the shape of the SPX90 Digital Multi-Effect Processor. This unassuming 1U high black box can provide its user with every signal processing effect imaginable bar one: aural excitement - though that's not to say that the SPX90 won't delight your ears as well as your wallet!

As on the REV-7, you are provided with 30 preset effects which you can call up, modify, then store your handywork in any of the 60 user memories (31-90). Every programmable parameter of an effect, apart from the input level, can be stored in the non-volatile memory and recalled manually yourself from the front panel, or remotely with the aid of an additional remote control unit similar to that for the REV-7, or alternatively by use of a MIDI program change command sent from a controlling MIDI keyboard or sequencer.

Before launching into a marathon rundown of the myriad functions of the SPX90, it's worth briefly discussing the machine's tech spec. For those of you wanting to know whether this unit is an even cheaper version of the REV-7 digital reverb, the answer is 'yes' and 'no'. A quick perusal of the manuals tells you that both the REV-7 and SPX90 share common specifications - but in limited areas only. Both machines are 16-bit and both use the same sampling rate (31.25kHz) for the digital conversion process which manifests itself as a 20Hz-12kHz effect bandwidth - respectable enough as far as reverb is concerned. The reverb side of the SPX90 is simply not as sophisticated as the REV-7 though, having no user control over diffusion characteristics, a reduced initial delay time of 50 milliseconds maximum (99.9ms on the REV-7) and a slightly more inferior dynamic range. In its defence though, it does have a much longer reverb decay time - from 0.3ms up to 99 seconds!

The non-reverb factory presets of the REV-7 like delay, stereo flanging, phasing etc, have been adapted for the SPX90 and improved upon in terms of flexibility. What Yamaha have also done is incorporate new effects on the SPX90 such as a compressor, panner, noise gate and pitch changer whilst integrating the non-programmable parametric equalisation section of the REV-7 as a separate programmable effect in its own right. All effects can be selected via MIDI, though MIDI control is not limited purely to that operation as you shall discover later.


As you can see from our photograph, the front panel of the unit isn't exactly crammed with features. On the contrary it is almost bare in comparison to the REV-7, the reason being that nearly all hardware functions are now performed by the software. A green liquid crystal display now supplies the necessary information on individual control settings with a red LED window indicating the selected memory location. The main front panel controls that exist come in the form of paired increment/decrement pushbuttons along with separate buttons governing the store/recall functions and control parameter selection. These all have multiple functions depending on the effect you've selected.

The SPX90 always powers up with the last memory location that you had displayed before the unit was switched off. To alter this, you step through the memory locations using the far right increment/decrement buttons until you reach the number you require. The memory display flashes until you press Recall whereupon the selected preset program becomes active. You can then edit this if you wish by selecting the various parameters that make up the effect one after another and changing their respective values. This is achieved easily by pressing the Parameter button, reading the display to see which parameter it is you've selected, then stepping the value up or down. You then press the Parameter button again to move on to the next parameter and repeat the edit process. This can all be done live so you can hear the effect your modifications have on the input signal but the altered program settings will be erased if you call up another memory unless you first store them, of course. You can't store modified versions of the presets in any of the first thirty memories, so what you do is recall a preset, edit it, change the memory location number for one between 31 and 90, then simply press Store and your program will be written into that location and remembered even when the power is off.

Adjacent to the parameter value buttons is a function button called 'Balance'. This allows you to programme the percentage mix between the dry and effected signals. Pressing the button again changes its function to that of an output level control.

Of the remaining front panel buttons, the most important one is 'Utility' which accesses certain modes that permit you to do such interesting things like edit the program title in the display and construct a new name for each effect using the stored alphanumeric characters (which include Japanese symbols!).

Pressing 'Utility' a second and third time accesses the MIDI control and MIDI program change functions of the SPX90. As with Yamaha's D1500, you can assign a particular memory to be selected automatically when a specific voice is chosen on a connected MIDI synth, for instance. Program voice numbers between 1 and 128 on the synth can be married up to individual memories of your choice and you can set individual Bank MIDI receive channels too. For, in fact, the SPX90 allows four Banks of program/memory combinations to be set up altogether, meaning that any one synth voice can call one of four different memories depending on which Bank is selected. And as this selection process can be programmed and recalled, it can be done in advance of a gig or session.

The final Utility mode sets the memory recall range for selection via a footswitch that plugs into the front panel jack socket. What you do is define the first and last memory number that you wish the footswitch to step between eg. 27 and 33. Successive depressions of the footswitch will then increment the memories sequentially from 27 to 33 then back to 27 and so on. By setting the highest number first you can even make the footswitch step through the selections in reverse order ie. from 33 down to 27. This function should prove invaluable on stage.


The 30 preset effects in the SPX90 cover variations of the following basic program types: Reverb, Early Reflections, Delay, Echo, Modulation Effects (stereo flange, chorus, stereo phasing, tremolo and symphonic), Pitch Change, Freeze, Pan, Vibrato and Parametric EQ. As I said earlier, a rackful of effects in a single box - and all for a mere £599.

Each effect has its own combination of related parameters which are all different and a detailed description of what every single one does is best left to the SPX90's user manual. For now I'll merely outline them whilst pointing out deficiencies where they occur.


Four very natural-sounding reverb programs are provided: Hall, Room, Vocal and Plate. As expected control parameters are supplied that govern the overall reverb time (0.3ms 99sec); the absorption ratio of high frequencies (0.1-1.0) - to simulate the sound absorbing qualities of various room surfaces; the initial time delay between hearing the original sound source and the reverb (0.1-50ms) - which effectively defines the room size. In addition, the low and high frequency content of the reverb can be moderated using the variable High-pass (32Hz-1kHz) and Low-pass (1kHz-11 kHz) filters. The cut-off points of these filters can even be modified in real-time whilst the reverb is functioning to create some unusual swept filter effects on the reverb tail.

Early Reflections

These provide two groups of four reverb simulations: Hall, Random, Plate and Reverse. The differences are in the density or close-spacing of the sound reflections that form the reverb. The Reverse setting recreates that ethereal effect of backwards echo/reverb. With these presets you also have control of the room size from 0.1 cubic metres (a small box) up to a staggering 100 million cubic metres (a massive cavern); the acoustic liveness of the room; the initial delay (0.1-400ms); and the high frequency content - again using a Low-pass filter.

Echo & Delay

These share the same number and type of variable parameters, the difference is in the maximum available delay range: 0.1-500 milliseconds (half a second) for Delay and only 0.1-250ms for Echo. Not very long times really. The saving grace is that both are stereo and allow independent setting of both delay time and feedback for each channel so you can generate some excellent double and triple-tracking effects for thickening up vocals and synths. There's also a High parameter which rolls off the top-end signal to simulate natural echo or old-fashioned analogue tape echoes.


Presets 9 to 15 cover the range of modulated delay effects like stereo flanging, chorus, phasing, tremolo and what is deemed 'symphonic'. This latter effect is a subtle variation between chorus and flanging without feedback. The parameter variables are common to all of them and range from Modulation Frequency (speed) - 0.1-20Hz, Depth, Delay Time - 0.1-100ms, and Feedback Gain. They function in an identical manner to every other flange/chorus device.


The SPX90 offers a comprehensive single channel noise gate program which allows the gate to be triggered externally from a MIDI keyboard. However, this gate has also been combined on several presets to create the archetypal 'gated reverb' effect much-heard on modern drum recordings. There's also a 'reverb with gate' program which gives you control over the gate function for creating a more varied selection of effects.

But back to the gate itself. The all-important threshold is set by the Trigger Level parameter whilst Trigger Delay permits you to offset the opening of the gate after a trigger has been received by any amount up to 100ms - best used on reverbed drums. A clever Trigger Mask feature prevents the gate from being re-triggered within the set time which can be anything from 5ms to 32 seconds! Further parameters are provided covering the Attack, Decay, Hold and Release times of the gate - also programmable up to 32 seconds. The level at which the gate remains open once triggered can also be set individually.

The exact same functions are made available on the Compressor.

Pitch Change

This is the most interesting section of the SPX90 as it is responsible for the creation of some highly usable stereo harmonising effects that are not plagued by glitching problems. Course pitch shifts of one octave above and below the original input are possible incremented in semitone steps. Fine tuning adjustments can then be made in one cent (one hundredth of a semitone) steps. On two of the four available pitch presets you can utilise the Delay control to produce echoes (up to 400ms) then feed the shifted signal back on itself to create unusual echo treatments that rise or lower in pitch on successive repeats. Set at a suitable pitch interval, this facility can generate fake arpeggios from a single note.

The problem with automatic pitch shift devices generally is that once an interval has been chosen, you're stuck with it and it's not always applicable to the music. That is unless you can vary the pitch shift in accordance with the input signal. Previous manufacturers of such harmonising devices have used a keyboard to perform this function, which is what the SPX90 does except it relies on a suitable MIDI keyboard. You need only set the 'base key' parameter to tell it where you wish the two octave span to fall on the keyboard. If the base key is C4 (Middle C), say, then pressing key C5 would produce a harmony note one octave higher.


Two freeze modes are possible which allow you to record, or should I say 'sample', a 500ms long signal into the SPX90. Recording can be set to start manually or automatically once a signal above a threshold level has been received. The program variations suit different functions. The first let's you sample a sound and then edit it by varying the start and end points but doesn't give you any control over the playback pitch. This is ideal for one-shot samples that you may want to trigger from a sequencer or drum machine. The second variation omits the editing control but automatically loops the 500ms sample and places the pitch under control of a MIDI keyboard if you wish, providing you with a monophonic keyboard sampler (albeit a very limited one).

Pan & Vibrato

It's interesting to see the inclusion of a panning device on the SPX90. Most of this unit's potential customers are unlikely to already own a panner or be thinking of buying one I'm sure - it's not exactly a vital piece of studio gear is it? But it's provided for that special occasion when the need arises.

Both auto-panning and comprehensive triggered panning (via MIDI if required) are provided on this preset with control selection of pan speed (0.1-20Hz), depth, and direction of pan: left-right, right-left or both simultaneously.

The vibrato program is comprehensive too but I can't really see a situation where you'd wish to use a 32 second delayed vibrato effect. This can be triggered from a note-on signal transmitted by a MIDI keyboard if so desired.

Parametric EQ

Preset 30 offers a two band, fully variable, true parametric equaliser section which has an enormous range of possible applications in both recording and live contexts. Its live application is further enhanced by the inclusion also of High and Low-pass 6dB/octave filters which can remove rumble and top-end hiss on a PA system, for instance.

I referred to this parametric as being 'true' for it actually provides control of the signal bandwidth or 'Q' as it's called. I must level criticism at Yamaha though for only providing two frequency bands: High sweeps between 800Hz and 8kHz whilst Mid encompasses 315Hz to 4kHz. But what about the all-important bass-end? It's exactly in this frequency region that a parametric is of immense benefit, especially for corrective use on drums. Why not rectify the matter and issue a software update immediately that includes a Low frequency band sweepable between, say, 30Hz and 500Hz?


When a manufacturer tries to combine several signal processing effects in a single unit, he's always in danger of compromising some of the features with the end result that only one or two effects are of real practical use anyway. Well I am glad to be able to report that this is definitely not the situation with Yamaha's SPX90. All of the preset effects, with the possible exception of delayed vibrato, are good quality and highly usable, though one or two fall below par in comparison with equivalent dedicated devices. MIDI control is always a welcome inclusion on any signal processor in my book and the SPX90 applies that control in some well-conceived areas such as for triggering the gate and harmony note selection.

There are some obvious and slightly incomprehensible limitations nevertheless. Restricting the maximum available delay time to 500ms is one - the extra memory required to produce a longer delay wouldn't add a fortune to the existing price. I don't understand why Yamaha deleted the rather excellent D1500 delay line, if this is all they intend to replace it with. Perhaps there's a successor to that unit already on it's way? If there isn't, there should be because they are presently losing sales to Korg and Roland who both produce good MIDI-controlled delays.

The same 500ms delay time is necessarily an equal limitation in freeze mode too. It restricts sampling to short duration material only.

Strange too is the provision of bandwidth controls on the parametric equaliser when the frequency range covered by the two bands goes no lower than 315Hz. A fixed bandwidth with extended low frequency coverage would have been infinitely more practical.

The reverb programs are what will attract the majority of customers to this device. After all, apart from the new Alesis MIDIVERB, there isn't another product that can compete with its reverb facilities in this price range.

To conclude, contrary to popular opinion, I believe the SPX90 will actually help stimulate interest in more sophisticated dedicated signal processors amongst its many users rather than prevent them from buying. There are still many people unaware of the role a compressor or gate plays in the recording process simply because they can't afford one having splashed out on a good quality reverb or delay. The SPX90 should therefore be of enormous educational benefittothem.

To genuinely criticise Yamaha for the few deficiencies in this product would be unfair; after all, there was nothing on the market previous to its arrival that came close to offering the flexibility and variety of functions provided by the SPX90. It is unquestionably destined to become the standard piece of processing gear in many different types of studio/home set-up. Another milestone? Absolutely.

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Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Apr 1986

Donated & scanned by: Bill Blackledge

Gear in this article:

Studio FX > Yamaha > SPX90

Gear Tags:

Digital FX

Review by Ian Gilby

Previous article in this issue:

> Slap 'n' Tickle

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> Beat Box

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