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Hands On: Yamaha SPX90

Article from Sound On Sound, December 1991

David Mellor offers advice to the studio newcomer on the original multi-effects unit.

Even though the Yamaha SPX90 is almost as old as Sound On Sound magazine, it can still lay claim to being one of the most popular effects units around. I have an SPX90 in the effects rack of my personal studio, and SPX90s are to be found in virtually every studio up and down the country and across the world, it has been that popular. In its day, it was considered little short of a miracle that so much power could be packed into such a small space. Even now, the sound quality of the SPX stands up to scrutiny, making it one of the most desirable pieces of equipment on the secondhand market. The SPX90 was discontinued some time ago, but it has a latter-day descendent in the form of the SPX900, which as you might guess is a revised and more up-to-date version of the original.

This latest installment in the Hands On series is aimed at the studio newcomer who wants to know what a multi-effects unit can do, how to operate it at its best, and how to bluff one's way into being thought of as an expert in the use of effects! Experienced studio engineers will know all this already, but hang on a minute... I bet you haven't used the SPX recently, what with the spate of multi-effects units that have come on the market since its launch. Give it a try and remind yourself of the simplicity of operation (for a digital unit) and the perhaps not astounding, but basically very good audio quality. You may be surprised, and find yourself turning to the SPX more often than more recent multi-effects devices.

The history of digital effects units is not a long one. The first of the modern generation of effects was the Yamaha D1500, a digital delay which originally sold for about £600. I picked one up at the end of the run for half that, and I use it still. The key feature of the D1500 was that it sported a trio of the now ubiquitous MIDI sockets. "MIDI on an effects unit?", people asked at the time. It was only for program change, and only a choice of 16 programs at that, but it was a start, and now we expect MIDI controlled everything on our effects units. The SPX90 came along shortly afterwards and it caused amazement in the industry. A good reverb unit, with delay, chorus, flanging, and sampling and pitch changing on top of that. For the price (£600-ish, which was really cheap in effects unit terms at the time) it was totally brilliant.

Of course at that stage, units which could perform more than one trick at a time were not available — although the SPX90 can produce several quite different effects, it can't produce them simultaneously. I remember that at the launch of the SPX, a studio representative asked when Yamaha were going to make such a unit. The reply was that you could have a device which would produce three different effects simultaneously for a mere £1,800 — three SPX90s!


As with all pieces of equipment, there are some things the SPX90 does well, but not all of its functions will find everyday use. For instance if you want a compression effect, which is available on the SPX, you would actually be a lot better off using a dedicated compressor. The specification of the unit shows where the problem lies: although the resolution of the digital encoding is 16-bit, the sampling rate is a mere 31,25kHz which gives an audio bandwidth of 12kHz. This causes a noticeable dulling of high frequencies and makes some effects unusable — or at least you wouldn't use them if you had alternative means to hand. Having pointed out that one deficiency, I can report that the noise and distortion performance is good.

Let's first list all the effects that the SPX90 is good at: Reverb; Early reflections; Delay; Chorus; Flanging; Pitch change; Vibrato; Autopan. And now the ones that are not so good: Compression; Gating; Equalisation. That leaves out one effect — sampling. When it first came out, the sampling function on the SPX was useful as decent samplers were pretty thin on the ground. But since virtually every studio has a proper sampler these days, it's unlikely that you would want to sample with an SPX. I will therefore leave this feature out of my Hands On guide, but if you want to experiment you can have some good fun with the two 'Freeze' programs.

The SPX90 has 30 preset programs which are selected with the right hand up/down keys and loaded with the Recall button. There are a further 60 user program memories, but I tend not to use these as it is incredibly easy to erase them by accident — just press Store instead of Recall! A lot of hard work can go down the drain that way, and anyway I prefer to tailor my effects to the material I'm working on rather than develop standard effects programs. So now you know all there is about selecting programs, let's get right into the interesting stuff...


There are four preset reverb programs on the SPX90: Hall, Room, Vocal and Plate. These are not the best reverb programs in existence, but when you're using your main reverb on something else, they can come in very handy. Of course this may just be my personal preference showing here. I was talking to a well-respected engineer a while ago, working at one of the country's largest studios. I asked him what reverb he was using on the mix of a 48-track digital master tape. "SPX90", he replied — the good old SPX must having something going for it!

The four preset programs are all subtly different, and obviously the Room program gives a 'smaller' reverb than the Hall, but the only way to decide which is best for your purpose is to try them out on their standard settings. Once you have picked the most appropriate, it's time to start editing it to taste. To edit on the SPX you select the parameter you want to adjust with the Parameter button (surprise, surprise), and change its value with the familiar up/down buttons. Pressing Parameter repeatedly on the Reverb programs will cycle the parameters through Rev Time, High, Delay, HPF and LPF. Let's see what these do.

Rev Time is simply the time it takes for the reverberation to die away by 60 decibels — this is the standard definition of reverberation time. The longest time available, 99 seconds, is unlikely to find much use. I find times around two seconds suitable for general reverb purposes. On any other reverb unit I would often be inclined to use a very short reverb on individual instruments that need a little 'extra'. But when you dial in a very short reverb on the SPX, it tends to sound a bit like a hard tiled bathroom with a very bright flutter echo. That may be nice when you want it, but it's not for general use.

The next parameter, High, governs the amount of high frequency reverberation (though it doesn't cure the problem mentioned above). In a real room, surfaces may be hard or soft. Hard surfaces reflect most of the sound that falls upon them, soft surfaces such as carpets or curtains absorb high frequencies but allow low frequencies through to be reflected by the structural floor, walls and ceiling. Since reverberation consists of a multitude of reflections, each of which bounces many times off the various surfaces, it follows that in a room with soft surfaces, the reverb time at high frequencies will be shorter than at low frequencies. This is often referred to as high frequency damping.

If you will permit me, I will give a different explanation of the next parameter, Delay, than is usually offered. You can probably look up the other one in a book, but I think I'm more correct! As explained above, reverb consists of a mass of reflections of the original sound, which is digitally simulated by a large number of delays. Used as an effect in recording, reverb can enhance a sound, but will sometimes reduce the clarity too much. The answer is to delay the reverb slightly so that the original sound comes through first, followed 50 to 100 milliseconds later by the reverb. This trick works particularly well on vocals, and is handy on drums too, but expect to listen carefully to the sound you are achieving. To get good results from an effects unit, you don't just slap in a preset and hope for the best, you fine tune the effect very carefully indeed.

The other two parameters are simply high and low pass filters. You don't need really to bother about these if you EQ the reverb on the mixing console. Whatever reverb settings you use, you will need to balance the direct sound with the reverb signal. The SPX90 has a Balance control, but don't use it! Balance the reverb using the aux sends and returns on the console; if you balance internally in the SPX you will unnecessarily degrade the direct sound to a 12kHz bandwidth.

Related to reverb are the two Early Reflection programs. These simulate the first few reflections of sound in a real room, but not the mass of reverberations that occur later. Early reflections really give life and sparkle to dull sounds. You wouldn't want to use these programs at a noticeable level, but subliminally so that the effect doesn't become too obvious. The two Early Reflection programs are very similar, except that Early Reflection 2 has a higher density of echoes. Both have the same parameters: Type; Room Size; Liveness; Delay; Low Pass Filter.

The 'Type' of early reflection sets the pattern of delays and intensities of the echoes. You can only judge them subjectively by trying out the four alternatives of Hall, Random, Plate and Reverse. The Room Size parameter is fairly self-explanatory: it increases or decreases the time between reflections to simulate larger or smaller rooms. Also self-explanatory is the Liveness parameter, which controls the simulated softness or hardness of the room's surfaces. The final two parameters, Delay and Low Pass Filter are similar to their equivalents in the Reverb programs.

Programs 5 and 6 are called respectively Delay L, R and Stereo Echo. As far as I can work out, they are exactly the same apart from different parameter settings and a total delay time of 500ms per channel in the former and 250ms per channel in the latter. The conclusion is that you can totally ignore program 6 because Delay L, R will give you all you need with the unit's maximum delay time of 500ms, which is quite enough for most purposes. Of course, you wouldn't expect the delay program to be quite as comprehensive as those found on the up-to-the-minute Sony DPS-D7 (reviewed last month) but the basics are there alright. As well as variable delay time (which can be different in the two channels) you have control over feedback, which produces multiple echoes varying from just a few to an almost infinite number, and high frequency damping which cuts off a bit of top each time the echo goes round, creating a more 'natural' sound.

Also coming under my heading of Reverb and Delay come programs 16, 17 and 20, a little way off from where they should have been located (among the other reverbs). Program 16 is a gated reverb, ideal for the Phil Collins sound that was trendy when the SPX90 first came out. Program 17 is a Reverse Gate which turns the natural envelope of reverb the other way round so that the reverb increases in level before cutting off sharply, rather than decreases. Program 20 is another gated reverb, but with a slightly different sound to Program 16. This program, of the programs I consider to be usable, has the honour of being included amongst those with no fewer than nine adjustable parameters, which are: Reverb time; High frequency damping; Delay; High pass filter; Low pass filter; Trigger level; Hold; Release; MIDI trigger.

The last four parameters are concerned with setting the level at which the gate will open and allow the reverb to pass. Thankfully, the standard settings work nearly always. The MIDI trigger is an added bonus, but I bet you never use it!


Once upon a time we had nasty noisy analogue phasers, chorusers and flangers, and we used them all the time because there was no alternative. Now we have modern digital equivalents, and we don't use them because they don't sound so good as the old timers. The phase type effects on many digital effects processors are a bit 'thin' compared to the real (analogue) thing. But the transistorised versions really were noisy and difficult to work with, and a digital box like the SPX gives a good, easy-to-use effect. There are six programs I can put under this heading: Stereo Flange A; Stereo Flange B; Chorus A; Chorus B; Stereo Phasing; Tremolo; Symphonic. Of these, I particularly like Flange A, basically because I don't have to alter the default parameters very much to get the sound I like. Flange B is a very similar basic effect (it may be identical) with the parameters at different settings. As with other flangers those parameters are: Frequency; Depth; Delay; Feedback. The frequency parameter obviously sets the rate at which the flange effect 'wobbles', and the depth by how much it wobbles up and down. The delay time sets the frequency range over which the flange operates (flanging causes peaks and dips in a signal's frequency response). A short delay creates flanging at high frequencies, a longer delay lowers the frequency at which the effect is heard. Feedback simply sends a portion of the output signal back to the input to be effected again. If you turn this up to a high value, you will hear a tone drifting up and down in pitch.

The flanging effect is used to 'enrich' a sound. Chorusing attempts to multiply the number of instruments playing by, in this case, splitting the input signal into three and panning the three signals to left, centre and right. Each signal is delayed and the delay time modulated up and down. The Symphonic program (Program 15) sounds like an 'ultra' chorus, with a very strong effect. You don't get many parameters to play with though, just modulation speed and depth. By the way, the Tremolo effect isn't what you would expect, ie. modulation of the amplitude of the signal. It is similar to Chorus, but with wider ranging parameters.


When the SPX90 arrived on the studio scene, the wonder of it was that at a mere £600 or so it had pitch changing as one of its functions. In fact, the quality of the pitch change can be considered to be pretty good even now. Of the four preset pitch change programs, I mostly use Pitch Change A and Pitch Change C. The A version has one pitch changer with coarse and fine controls to shift the tuning up or down up to an octave. There is also a delay, which you would use if you were adding a pitch changed effect signal to an original for the purpose of thickening it up. Actually, I don't usually like delayed pitch change so I set it to the smallest value possible. Pitch Change C is similar to A, apart from not having one of A's parameters which I haven't mentioned yet, and it produces two pitch changed outputs. This is a vocal fixer without compare. Put an 'iffy' vocalist through this with the left channel set to +8 cents (1 cent = 1/100th semitone) and the right to -8 cents, mix in equal proportions with the original signal, and any slight out-of-tuneness is covered up completely. You wouldn't want to treat a good vocalist in this way, but when you don't have the choice it's an excellent way out of a sticky situation. I have also used the pitch changer on a vocalist who was good but who hit the occasional sharp or flat note. All you do is cycle the tape around the offending section, find the degree of pitch change that corrects the tuning fault, and then simply drop the correction into the track! (Actually it's best to do it on a copy of the vocal track in case you slip up).

For admirers of the weird and wonderful. Pitch Change A has another trick courtesy of that extra parameter I mentioned — feedback. Set the pitch change to +4 semitones, the delay (which now finds its true function) to around 100ms and the feedback to 80% and hear an amazing upwardly spiralling pitch changed echo effect. Best not to over use it perhaps.

At the (original) new and current secondhand prices I can't overpraise the pitch changing effect on the SPX90. (That's just put the secondhand price up by 20% — sorry). As if all these excellent effects weren't enough, the SPX90 has a couple more decent tricks up its sleeve. Autopan is a great effect when you're at the stage of thinking "What can I do to make this track more interesting?". The standard settings are not what you would typically want so may I suggest a speed of 0.7Hz (unchanged), a direction of L<>R and depth of 100%. This will swing the signal back and forth between the two outputs and make the people who listen to your final mix on headphones seasick. If you only use one output, setting the speed to 5Hz and the depth to 60%, you've got yourself a great tremolo too. A real one this time.

The Delayed Vibrato is another great effect, but the standard settings are all up the spout. Try these settings as your starting point: Trigger level, 100; Delay, 1ms; Rise time, 5ms; Frequency, 3.5Hz; Depth, 10%.

What you'll get is a smooth cyclic pitch change which will enhance just about anything you care to put through it. All it takes is knowing that the effect is there in the rack, waiting for you to use it.


1 Reverb 1 Hall 16 Gate Reverb
2 Reverb 2 Room 17 Reverse Gate
3 Reverb 3 Vocal 18 ADR Noise Gate
4 Reverb 4 Plate 19 Compressor
5 Early Reflection 1 20 Reverb & Gate
6 Early Reflection 2 21 Pitch Change A
7 Delay L, R 22 Pitch Change B
8 Stereo Echo 23 Pitch Change C
9 Stereo Flange A 24 Pitch Change D
10 Stereo Flange B 25 Freeze A
11 Chorus A 26 Freeze B
12 Chorus B 27 Auto Pan
13 Stereo Phasing 28 Triggered Pan
14 Tremolo 29 Delay Vibrato
15 Symphonic 30 Parametric EQ


I'm all for making life simple, so when you find yourself confronted with a Yamaha SPX90, it'll help if you know which programs are good, and which you can safely ignore until you want to experiment. So here is my opinion on the subject. I've indicated in brackets whether you need to add the effect via aux sends and returns or as a straight through effect, probably in the console's channel insert point.

Reverb (aux)
Early Reflection (aux)
Stereo Echo (aux)
Stereo Flange (insert)
Chorus (insert)
Stereo Phasing (insert)
Reverb and Gate (aux)
Pitch Change (either)
Auto Pan (insert)
Delay Vibrato (insert)

Symphonic (insert)
Tremolo (insert)
Gate Reverb (aux)
Reverse Gate (aux)
Freeze (aux send/return to channel)
Triggered Pan (insert)

Noise Gate (insert)
Compressor (insert)
Parametric EQ (insert)

Don't take this as a warning not to use certain effects. It's just that I think you would be better off using specialised units for dynamics and EQ. In conclusion, I can say that the Yamaha SPX90 is still an excellent unit to have in the effects rack. I certainly won't be selling mine (unless it becomes a valuable antique one day) and you need not look for SPX cast offs from any studio where the engineers know a good thing when they see one. But if you cast your eyes down the secondhand columns of this magazine, or check any of the other well known sources of used equipment, you might just see an SPX90 that has been abandoned by an owner who has forgotten just how good it still is. Snap it up!


Shortly after the introduction of the SPX90, Yamaha introduced a revised version of the unit known as the SPX90II. The MkII version was identical to the original, apart from the fact that the maximum delay increased from half a second to two seconds, and the range of some of the parameter values expanded (but they were already adequate for most purposes). Unless you particularly want to use it for the Freeze (sampling) programs, I can't see a lot of benefit, and paying a higher secondhand price for a Mark II wouldn't really be justified.

The SPX900, however, is a totally new machine. The sampling rate has been increased to accommodate a full 20kHz bandwidth, and up to five effects can be used simultaneously. The increased quality and versatility place it a cut above the SPX90 and SPX90II, but of course you will have to expect to pay more for it (not least because it's a more recent product). It's a good unit, but the original SPX90 has to be the classic model.

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

The current copyright owner/s of this content may differ from the originally published copyright notice.
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Sound On Sound - Dec 1991

Donated by: Bert Jansch / Adam Jansch


Effects Processing

Gear in this article:

Studio/Rack FX > Yamaha > SPX90

Gear Tags:

Digital FX

Feature by David Mellor

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> Born In The USA

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