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Fade away and radiate

Article from The Mix, May 1995

Bob Dormon's effects tutorials conclude with a look at multi-effects units

Multi-effects devices are usually next on the list after buying your first multi-track. It's hard to imagine recording without them, yet they've only been around for about ten years. Bob Dormon sheds some light on these small objects of desire...

The passing of time certainly offers new developments, but in some cases you can't beat a great idea, only refine it. Yamaha's SPX 90 was, and still is a great idea. When it was first unveiled, the industry found it hard to believe that a 1u rack unit was capable of doing so much, and for only £629. These days, its successor the SPX 900 certainly isn't alone in its field, but the original SPX 90 still gives you an idea of what to look for when shopping around for a second-hand multi-effects device.

I chose this now discontinued golden oldie to be fair to other manufacturers, who provide a magnificent range to match every budget. However, if anyone does think that to spotlight a nine year old effects device is unfair competition, then all I can say is you've had plenty of time to catch up!

Welcome to the machine

Why might you need a multi-effects device? Well, usually that question is answered by two things:-

i) your recording needs.
ii) how much money you have to spend.

Simply, a multi-effects device offers more 'bang per buck' as our colonial cousins might say. While more expensive dedicated effects devices such as delays and reverbs offer classy textures and a sonic purity that is beyond the grasp of many budget devices, what a multi-effects device can provide is a complete paintbox, enabling you to tint your sounds with a variety of colours, rather than being stuck with just charcoal or pencil.

To hear first hand what this means, then check out this month's Re:Mix CD Effects Tutorial, part II. All the sounds were in some way 'effected', by an SPX 90 effects program. In essence, what a multi-effects device should offer is not only a number of reverb programs (or algorithms), but delay effects, plus chorus flanging and phasing. Also pitch change (or harmoniser) and panning treatments. Frequently, a compressor and a noise gate are among the available algorithms, while some devices offer distortion effects for guitars, aural exciters, equalisation and basic sampling. Today's models offer further sophistication, in that you can feed a number of effects into each other. For example, with say a guitar, you can add chorus, then some echo, and finish off with a dab of distortion, all within the same box. Thus the device becomes a true multi-effects unit, in that it can create a number of effects simultaneously, rather than just having a number of individual effects to choose from.

Parameters pay

Part one of this series of effects tutorials, back in the February issue, included methods of creating effects using a simple digital delay. Sometimes, no matter how much tweaking you do, the sound you're after escapes you. It may be due to inexperience or certain limitations of the equipment you're using. With a multi-effects unit, you're given the opportunity to just prod and play, as all the work has been done beforehand.

You want chorus? Then select your chorus program. Fancy a stereo echo? Well, it's there too, the only thing you have to remember is that some adjustment may be necessary to get the echo timing right. The same goes for reverbs. They sometimes need modifications to the decay times or room size, but it's simple enough once you start. That's usually the biggest hurdle for anyone new to this type of technology. Making your own adjustments is precisely what you need to do, to knock these treatments into shape so that they complement your music. Preset programs are a great first step, but if you don't personalise them, they can often draw attention to your music in an undesirable way, simply because it sounds weird not wonderful.

On the more versatile effects devices, the functions you need to adjust are frequently found under the 'parameters', or 'edit', headings. Indeed, what you alter are the parameters, namely particular stages in the effects program or algorithm that can be adjusted. What keeps the bashful from investigating further into the workings of effects units, is the concern that they'll bugger it up and lose their favourite preset program.

The SPX 90 — like many of its current contemporaries — has all its preset programs stored on a ROM chip. This is a permanent record of the factory program settings, which can't be erased. What you can do is use the preset programs as a template, and then store your adjustments in the user memory locations. Whatever you do, the original preset programs can't be lost, and will always be there in the morning... provided you haven't been burgled.

Bob Dormon would like to thank Phil Strongman for wearing tape op's hat during the preparation of this month's effects tutorial.

Modulation Effects

What made so many of the SPX 90's effects so popular was that they were stereo. With some of the modulation effects, the modulation frequency determines the rate at which the effect's stereo image shifts from left to right and back again. It doesn't matter if the effect is mono either, because a properly set modulation frequency will still give pleasing results. Actually having the modulation frequency parameter specified in Hertz (Hz) allows you to accurately program the panning or LFO effect so that it beats in time with your music. Here's what to do:-

i. Calculate your delay time. You do this by dividing 60 by the bpm (beats per minute). If you don't know the tempo, then just count the beats over fifteen seconds and then multiply by four, and you'll have an approximate bpm.

e.g. 60 (secs) = 0.5 secs or 500 mS
120 bpm

ii. Calculate the frequency for that tempo by dividing 1 by your delay time figure.
e.g. 1 = 2Hz

iii. Enter the result as the modulation frequency parameter for the effects program.

This works for panning programs too. If the panning is too rapid, then divide the figure by two until you get the desired effect. If you want to create a shimmering chorus or flange effect for a guitar, you may want to double up this frequency figure a few times, so that it pulses nicely with the beat.

Flange, Chorus and Phasing effects have many control parameters in common. Modulation depth and delay modulation depth work in a similar manner, by varying the delay times by small amounts, producing slight detuning effects. Modulation delay time found on the flanger and phaser are identical to the delay or pre-delay effect used on reverbs, as they simply delay the time it takes before the actual effect kicks in. However, with these modulation effects, the times needed are very short. For example, 1 mS will affect the high frequencies more, while something around 3mS works on lower frequencies. With the SPX 90 Chorus program, you also get amplitude modulation. This parameter changes the level of the signal, so that it oscillates in time with the modulation frequency, producing audible variations in volume.

Parameters please

Pitch Change A-D

Pitch Change programs involve some pretty intensive calculations, in order to perform the task in hand. Before the SPX 90, this was the domain of the Eventide Harmoniser or the AMS dmx 15-80. Furthermore, the SPX 90 offers four pitch change algorithms, each with their own unique set of functions.

They all share the same pitch change range of ±12 semi-tones (coarse) and ±100th of a semitone in one cent intervals (fine). You can also set a delay time of up to 400mS (A,B,D) or 200mS on C. For programs A and D, a feedback parameter means you can vary the repeats, but with a difference. Each following repeat changes pitch by the interval originally set, producing some very interesting pitch-climbing effects. Pitch Change B and C allow you to set up two independent pitch changes. With B they come out of both outputs, but with C they are processed separately, with one appearing at the left output, and the other the right. Pitch change C has to be one of the most creative features of the SPX 90, because you can set a different delay for each channel too. I frequently use it to liven up percussion parts, so that mono bongos, tambourines or shakers can be delayed, pitched very slightly and then panned left and right. This produces a cascade of rhythm that has feel provided by the delay, and the new pitching plus the movement of the panning facility provided by separate outputs.

MIDI also plays a part in the function of Pitch Change A and D. You can externally control the pitching from a keyboard by setting up a 'base key', on these programs. If your base key was C3, then playing C2 on the keyboard would produce a pitch change down an octave. More adept musicians could then harmonise their vocals by playing the incidental keys required. Alternatively, if you wanted to take more time, you could control the pitch changes from a sequencer, so that you could accurately track every phrase from a brass line or sax solo.


Admittedly, sampling on an effects device would appear to be a very limited affair. The SPX 90's specifications are comprehensive enough, even if the result is, sonically, left wanting. This is, after all 1986 sample technology in a 1u rack! Freeze A can make quite a difference to a mix. If your drum machine doesn't have a shaker or tambourine, you can sample one into the SPX 90 and trigger it via MIDI, a footpedal or the front panel. Once you've sampled say a tambourine, you can also make it respond to incoming audio. Feeding in a snare from an auxiliary send will instantly trigger the tambourine sample, for that Peter Gabriel 'Sledgehammer' drum sound.

Freeze B can also be played back via MIDI, and you can pitch the samples too. The sampling allows overdubbing, so that you can stack backing vocal oohs and aahs. On the CD, I used Freeze B to make a vocal pad, by singing in individual notes to make up a chord that I then played back over MIDI. Freeze B automatically loops the sampled signal, so it's best to try and sample a sustained sound rather than the initial attack, otherwise things get a bit lumpy.

Compressor and ADR noise gate

Both the compressor and noise gate are fairly unremarkable in themselves, yet the MIDI applications are quite appealing. For both effects, MIDI note on and off will activate and de-activate their respective actions. So if your keyboard hums or buzzes, you can perform your own edits by having the beastie gated out until you begin to play. MIDI control of the compressor might have its best application in selectively compressing a track, by controlling the effect from a sequencer.

Each of these effects has fairly familiar parameters, with the exception of Trigger Mask. This is similar to the Hold Time, but actually makes it impossible to retrigger the effect until the trigger mask time has elapsed. As this timing range goes up to 32 seconds, you could set a gate or compressor to work over a whole verse or chorus.


As you can see from the program listing, there's even more to this box of delights. The gear that's around today should offer both cleaner and cooler sounds for even less money. Nevertheless, they'll always be a space in my rack for an SPX 90.

Factory Favourites

Although a variety of effects parameters were explained in February's effects tutorial, here's some of the more esoteric ones featured on the SPX 90, plus a brief guide to the typical settings found on the more common effects. What is appealing about Yamaha's layout of the effects parameters is the detail. Often manufacturers just give arbitrary figures, ranging from 0-100 or 0-127, rather than distinct measurements. Scrolling through specific figures can save a lot of time, when you know you want a 2 second reverb or a 250mS delay. Unless you're happy taking the time to do things by ear, non-specific values can be a trial of time and patience. Nevertheless, regardless of the yardstick used, the nomenclature of multi-effects devices is almost universal.

Reverbs 1-4
You couldn't really have a multi-effects device without including a few reverbs. The SPX 90 has five parameters that are used to simulate the four different factory presets (see list/box II), which appear as standard. As with all the effects, you can edit these, rename them and then store them in the user memory locations.

1. Reverb Time. (Range: 0.3-99.0 secs)
The manual studiously explains reverb time as, '... the length of time it takes for the level of reverberation at 1 kHz to decrease by 60dB — virtually to silence.' Basically, it's how long the reverb effect lasts before it fades away.

2. High (High Frequency Reverb Time Ratio. Range: 0.1-1.0)
This is a very useful, much misunderstood and overlooked parameter. High acts as a high frequency damper, enabling you to wind down the reverberation time of the high frequencies, without affecting the mid and low ranges. The range is a ratio, so if set to 1, the high frequencies last the same length of time as the other frequencies. But if set below 1, then the high frequency timing is shortened proportionately. Using this setting allows you to simulate different environments more accurately, from churches to carpeted cubicles.

3. Delay (Range: 0.1-50msecs)
This function is often referred to as pre-delay, and creates a time delay between the direct sound of the instrument and the actual reverberation effect. Changing this setting can help instruments to breathe a little, before the reverb kicks in.

4. HPF (High Pass Filter. Range: THRU, 32Hz-1kHz)
The HPF allows you to wind off the low frequency content of the reverb, and is very useful in helping contain unwieldy bass sounds. For instance, if your keyboard pad drones too much in the low frequencies when reverb is added, you can use this parameter to control those low frequency resonances. The THRU setting turns this filter off.

5. LPF (Low Pass Filter. Range: 1kHz-11kHz, THRU)
The LPF acts in a similar, but opposite way to the HPF. You use this setting to attenuate the high frequency content of the reverb. This isn't the same as High, because that changes the timing. LPF allows you to cut off a specific frequency range. Among other things this can be applied to reverbs, on vocals that sound too cold, or acoustic guitars that are too brittle and need warming up.

SPX 90 Program listing

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

On the RE:MIX CD

Bob's multi-effects tutorial features the combined talents of Yamaha's SPX90 (an overnight sensation when it first appeared in 1986) and his Irish wolfhound mongrel Si Si (never less than sensational).

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Dream sequences

Publisher: The Mix - Music Maker Publications (UK), Future Publishing.

The current copyright owner/s of this content may differ from the originally published copyright notice.
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The Mix - May 1995

Donated by: Colin Potter

Coverdisc: Nathan Ramsden

Sound Advice


Effects Processing

Gear in this article:

Studio/Rack FX > Yamaha > SPX90

Gear Tags:

Digital FX

Re:Mix #11 Tracklisting:

10 Multi-effects with Bob Dormon

This disk has been archived in full and disk images and further downloads are available at - Re:Mix #11.

Feature by Bob Dormon

Previous article in this issue:

> Mixed media

Next article in this issue:

> Dream sequences

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