Is the use of 20-bit technology in effects units a real advance or a marketing ploy? Paul White gets motoring with Yamaha's latest outboard and finds out.

During the mid to late '80s, the market was flooded with low-cost digital reverb and multi-effects processors from Japan and the USA which brought a new level of sophistication to both live and recorded sound. There's no denying the excellent value these units represented, nor the impact they had on the home recording market, but in this age of affordable DAT digital mastering and now digital multitrack, most of them let the side down rather badly in terms of noise and overall fidelity. What's needed now isn't simply new effects, but rather a new level of quality and professionalism so that effects units are no longer the weak link in the chain.

Yamaha have a huge advantage in this new quality conscious marketplace because they are one of the few music manufacturers large enough to make their own custom chips on a large scale, and their work on 20-bit professional audio systems has obviously paid dividends in enabling them to apply similar technology to their lower-priced products. For example, the product currently under review has 20-bit input and output conversion at a 44.1kHz sampling rate, which translates into a 20Hz-20kHz frequency response with a dynamic range of typically 106dB — 10dB better than an ideal 16-bit system. Not only does this ensure that the effects unit is more than quiet enough to use with 16-bit digital recorders, it also allows the user to reserve a respectable amount of operating headroom to prevent distortion occurring during signal peaks.

The SPX990 follows the original SPX tradition of providing a variety of effects from which to choose; an effects program can contain up to three effects, designated as Pre-Effect, Main Effect and Post Effect. This may seem limited considering that some units claim a dozen or more simultaneous effects, but Yamaha appear to have used their available processing power for quality, not quantity. There are four possible Pre-Effects, 36 Main Effects (some of which are really combination effects) and three Post Effects.

As is now customary, the unit's memory is divided into presets and user editable locations with a further memory area reserved for an optional memory card. Preset Memories 1-80 hold factory patches which may be recalled and used but not edited. User Memories 00-99 are user-editable locations which come filled with duplicates of the factory presets, and a further 100 user patches can be stored on an optional memory card which is loaded in via a card slot on the front panel of the unit.

HARDWARE

Packaged in the familiar black, 1U case, the SPX990 looks deceptively simple. The front panel button arrangement doesn't look vastly different to that found on its predecessors, but a data entry knob has joined the familiar increment/decrement buttons that characterised the early SPX units. The display comprises a backlit LCD window and a separate two-digit LED window which shows the currently selected patch.

Yamaha have clearly tried to cover both professional and semi-pro markets with this machine, as it comes fitted with both balanced XLR and balanced jack audio in/outs, the latter being switchable between -20dBv and +4dBu sensitivity. The sensitivity may be switched independently for both the input and output connectors, and the jacks are equally happy working with balanced or unbalanced plugs. However, I still feel mildly irritated that there is no -10dBv setting — the most common operating level in semi-pro and home studios. In addition to the two audio ins and the two audio outs, there's a MIDI In and a further MIDI socket which may be switched from Out to Thru. The most flexible degree of control is via MIDI, but two footswitch sockets are provided for those with simpler needs. These may be configured to operate as Bypass, Memory Inc/Dec and Trigger. Power is direct from the mains with no awkward mains adaptor to worry about.

PRE-EFFECTS

Though the 990 is relatively straightforward to operate, there are a great many effects parameters to which the user has access, the actual parameters depending on the effect selected for editing. To detail each one here would be to rewrite the manual, but there are some details worthy of particular note:

PRE EFFECT: This is always Parametric EQ, Compressor, Harmonic Drive, or Distortion.

EQ: This is a two-channel device (independently adjustable for left and right channels) and is a fully parametric, three-band affair with additional 12dB per octave low and high pass variable frequency filters, making it impressively versatile.

COMPRESSOR: The compressor option is also stereo and has parameters corresponding to a typical hardware, hard ratio compressor, including a built-in gate to minimise noise. My main reservation concerning digital compressors of this type is that there is insufficient metering of the compressor action. At the very least, there should be a gain reduction meter.

HARMONIC DRIVER: This effect is a digital implementation of a harmonic exciter and has Drive, Frequency and Mix controls, just like the real thing. The idea is that the frequencies below the frequency set by the user are unchanged, while the ones above it are used as the basis for creating musically related overtones which are then added back to the dry signal. This increases the overall sense of brightness and detail in a way that's quite different from conventional EQ.

DISTORTION: The Distortion Program actually includes compression and EQ, so could be considered as a multi-effect in its own right. It would appear that the input is compressed before the overdrive circuit and then EQ'd last of all so that any undesirable overdrive harmonics can be filtered out before further effects are added. The EQ is reduced to a two-band parametric in this configuration and the shelving filters are omitted.

MAIN EFFECTS

The list of Main Effects is huge (see box for a full listing of all 36 options). Most of these may be categorised as reverb, early reflection programs, delays, modulation effects, pitch-shift effects and pans, with some combination effects being provided in the Multi-Effects section. There's also a Freeze option, which can be used as a simple sampler. In the reverb section, there are rather more basic options than the usual choice of rooms, halls and plates, while the gated and reverse settings are included in the Early reflections section. All are editable in great depth, with reverb time, pre-delay, density, diffusion and damping being just a few of the available adjustments; even the conventional reverbs have in-built gate settings, allowing them to be used for setting up traditional gated room effects.

The delays include single and multitapped types, with various feedback options giving a whole range of delay and echo effects. The multitap program features six independently adjustable delay taps, the maximum delay time in this mode being 1480mS. A tap input front-panel (or footswitch) switch facility is featured, so you can set delay time to match the tempo of a particular piece of music, though tempo delays can also be set up using manual time entry, can be linked to the incoming MIDI clock rate, or set using MIDI control change information.

Moving onto the modulation effects, most of these fall under the phasing, flanging, chorus and vibrato blanket, though there are one or two specials, including Yamaha's classic Symphonic chorus patches, combining pitch modulation with amplitude modulation. All these effects may be used in stereo, including phasing, which emulates the sound of early phasing pedals.

"The plates sound bright and articulate, while the concert halls are deep and rolling with none of the metallic overtones that characterised some earlier Yamaha reverb units."

No multi-effects unit would be complete without pitch shifting, and the SPX990 offers a choice of traditional or intelligent shifting, the latter option being capable of tracking the notes being played and adding a harmony in real time.

You simply program the unit with the key of the piece of music and the type of musical scale being used. Seven of the most popular scale types are included as presets, though there is the option to create a further two user scales. Most pitch shifters can provide two different shifts at the same time, but the Triple Change patch produces three shifted notes in addition to the original, making it possible to play large chords from a single note. Alternatively, the intelligent option may be switched on to create four-part harmonies — serious butcher's shop quartet stuff! User scales may be programmed with the help of a MIDI keyboard, which may be easier than trying to accomplish the same thing entirely via pushbuttons.

I have to admit to being a big fan of pan effects, especially those that can be triggered from MIDI. In the case of the SPX990, Pans may be initiated manually or via MIDI and the attack and release time of the pan sweep may be set by the user. There's also a free-running pan which includes Yamaha's Round Panning algorithm — designed to make the sound appear as though it is moving in a circle rather than along a straight line between the speakers. This can be a useful treatment for pad keyboard sounds, though I would have liked to be able to trigger this type of pan over MIDI too. As it is, it's simply free running, though you do have control over speed, direction and depth.

Last on the list is Freeze, which amounts to simple, monophonic sampling. A maximum of 1350mS of sound may be stored, though this is lost when the unit is powered down or whenever a new program is selected. Recordings may be made manually by arming an auto-trigger function, and it is possible to overdub a new sound on top of that already in memory. The sound may then be trimmed to fine tune the start and end points, and played back on a one-shot basis or looped to form a continuous sound, such as a rhythm loop. The pitch of the replayed sound may be changed manually over a four-octave range or via MIDI, where middle C corresponds to no pitch shift, the maximum control range being C1 to C6.

Post Effects offer essentially the same choice as the Pre-effects, with the exception of Distortion, which is omitted. MIDI may be used to call up programs from the patch assignment table and also to load or dump the contents of the SPX990's memory via SysEx. Additionally, two effects parameters per patch may be assigned to realtime MIDI control using any control change message. Furthermore, MIDI gating is possible, as is MIDI pitch control when using one of the Freeze sampling patches. Likewise, the pitch shifting programs may be controlled from a MIDI keyboard or sequencer.

THE NITTY GRITTY

I must say that the manual appears to have been translated in haste from its native Japanese, but it still manages to convey all the necessary information in a more or less logical manner, even if some of the spelling and grammar is distractingly amusing. The user interface of this particular machine is reassuringly friendly, something which even Yamaha must agree can't be said of every product they've ever built. I like the way the relative novice (or lazy old timer) can simply pick out a preset and then edit it to fit the job in hand.

In this respect, the factory presets might more properly be considered as editable effect algorithms. But when it comes down to it, neither the effects on offer nor the user interface is in any way unique — what really matters here is the technical quality of the sound, the subjective quality of the effects and how those two variables equate to the asking price.

I was never a great fan of Yamaha reverb algorithms, but over the past year or two, they really seem to have taken great strides in this department and the reverb treatments on offer here are first class. Gone are the hard and nasty metallic rooms; instead we have bright, airy reverbs which are shimmering with character and warmth. There's lots of variety too, with stone rooms, bamboo rooms and even concrete rooms augmenting the more usual fare. The plates sound bright and articulate, while the concert halls are deep and rolling with none of the metallic overtones that characterised some earlier Yamaha reverb units. In short, I like both the character and variety of the reverbs provided here.

The modulation effects are rich and dynamic with plenty of width, though that's not so surprising; this is one area Yamaha got right a long time ago. Similarly the delays are squeaky clean, no doubt benefiting from the 20-bit conversion system, and the stereo multitapped delays are very flexible, especially when combined with a little EQ. My only gripe with the delays is that setting long delay times using the data entry wheel can involve a lot of turning — I was tempted to use my power screwdriver just to hurry things along! I also found the data wheel jumping to the wrong preset on occasions when I was changing programs. This may have been a one-off fault (either with the unit or me), but it's worth checking just the same!

I said earlier that the effects are quiet and well-behaved; in fact the distortion and Harmonic Drive programs tended to be a little hissy, but the vast majority of programs were excellent in this respect. It must also be appreciated that any program using overdrive, compression, harmonic drive or EQ boost will exaggerate any noise present in the input signal.

While focusing on dislikes, I'm afraid that budget pitch shifting still hasn't progressed far enough in the past half decade. Small shifts sound wonderful for detuning and thickening, but move the pitch by whole musical intervals and the shifted sound needs to be kept well down in the mix to disguise the metallic, rather discordant sound. This rather reduces the usefulness of the otherwise competent intelligent pitch shifting system, which doesn't come close to the Digitech Intelliverb for subjective smoothness.

Of the other effects, I found the distortion effect fine for keyboard work — as long as it is used in moderation — but it doesn't work well on guitar. The rotary pan effect is interesting, and I can envisage several applications for that, while the parametric EQ is both powerful and decent sounding if you have the patience to work at the settings. The Freeze sampler is nice and clean, and has a long enough storage time for small sampling jobs, but the fact that it is monophonic and that there is no simple way to store samples after use means that, although it's handy for trying out loops, it doesn't really offer an alternative to a conventional sampler, even a very basic one. Still, the unit wouldn't have been any cheaper to build had they left it out — so welcome aboard!

The time taken to change from one effect to another is creditably small, but you still have to time the changeover to coincide with a gap in the music if it isn't to be noticed. There's no glitch as such, but the effect level drops away rather suddenly and there's a moment of silence before the new effect comes in.

Rather than consider this as an all-singing, all-dancing multi-effects unit, I feel it might be better to view it as a superb reverb and delay unit (including modulation effects) with the additional effects thrown in as icing on the cake. Used properly, the reverb and delay effects are very nice indeed and they're also wonderfully quiet. Having EQ at the front or back end of the chain only adds to the versatility of the unit, but I'm afraid the compressor, harmonic enhancement, overdrive and pitch shifting effects just aren't in the same league. Being fair, the pitch shifting is about as good as you get in this price range, but the sound doesn't stand up to even casual scrutiny. Should you be in the market for a first rate reverb unit that can turn its hand to most routine and one or two not so routine jobs in between times, then the SPX990 has to considered as one of the leaders in its price range. It's also very easy to use, sensibly priced and it looks the business. Could this signal the end for 16-bit effects units?

Further Information

SPX990 £769 inc VAT.

Yamaha-Kemble, (Contact Details).