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Yamaha REX50

Digital Signal Processor

Article from Music Technology, October 1987

The latest signal processor from Yamaha may be aimed primarily at guitarists but the small studio owner might prefer to look at it as an adaptation of the SPX90. Rick Davies finds out it has a few new twists as well as a slimline price tag.

Now that digital multi-effects have broken the £400 barrier Yamaha have brought distortion and programmability into the game with the REX50.

UNASSUMING THOUGH IT may appear, a rack-mount chassis adds more to the cost of a musical device than you might imagine. Whether this has anything to do with Yamaha's decision to package their latest digital effect device, the REX50, in an attractive non-rack chassis remains to be seen.

At first sight, the REX50's sleek profile gives the impression that it might be at home on the floor alongside a set of guitarists' stomp boxes, but a closer look puts a swift end to that. The location of the LCD and LED windows and the small rectangular controls make it obvious that feet are not welcome on this front panel. The REX actually makes a nice "table-top" effect, space permitting. Weighing in at under four pounds, it's just the sort of unit to stick into a gig bag and haul along to a session. And that's not the sort of thing you do with an effects rack.


IN TRUE GUITAR effects fashion, the REX50 provides ¼" audio inputs and outputs on the back panel. This brings us straight to something which needs to be clarified - although the REX50 provides left and right inputs and outputs and stereo effects are possible, the inputs are not processed separately. Instead, they are summed and then processed together to produce stereo effects, after which you can mix the dry input signals with the effect. This makes the inputs suitable for running the REX50 as an inline effect for instruments (typically synths) with stereo outputs. For in-line guitar processing, plugging into only the left input sets up the REX50 for monophonic operation; though the dry input signal appears at both outputs.

Since inexpensive mixers or multitrackers tend to have limited effects send facilities, monophonic operation would seem to be most suitable for low-budget recording setups. There is no monophonic output option, and though it might seem like a waste not to take advantage of the stereo processing at every turn, a mono output would come in handy when there's a shortage of mixer inputs (for in-line operation or auxiliary returns), though there are only a handful of effects where this is a problem (as will become evident).

Completing the back panel are two ¼" footswitch inputs, which cater for effect bypassing and program selection; an input level trim pot - an improvement over the original SPX90 which only had an input level switch; a Stereo Mix toggle button for switching the dry input signal (s) in and out of the stereo outputs; and a single MIDI In port. The Stereo Mix button is only really effective if the effect/dry Balance parameter is set lower than 100% (which it isn't in any of the factory presets, by the way), but it does provide a simple way to go from in-line to auxiliary operation without having to reprogram the REX. The omission of other MIDI ports ceases to be a shortcoming when you notice how tidy Yamaha have been in packing the rear panel. To add more inputs or outputs surely would have required a larger chassis, and consequently a higher cost, so this isn't likely to spoil the picnic.

Like other Yamaha pro audio gear, and unlike so many of their musical instruments, the REX50 connects directly to power outlets rather than relying on a detachable power adaptor - a pleasant surprise from such a low-cost device.

Program Selection

THE CONTROL PANEL is tiny, with a mere eight switches handling program selection, editing, storing and bypassing functions. On power-up the REX50 is in preset mode, and any of the 90 effects programs can be easily recalled by adjusting the program number in the LED window using the up and down arrow switches, and then pressing Recall. This is a reasonable alternative to having a keypad for random access to programs, and certainly delivers the goods with minimal controls. As each program number is displayed, the LCD window shows the program name ("Rev Reverb & Gate", "Distortion + Rev Plate" or whatever).

There are two alternatives to this method of program selection. One is to use MIDI Program Change command; the REX accommodates these with four separate lookup tables, each with a corresponding MIDI channel, so it can respond differently to four MIDI sources. Not exactly a mainstream application, but it's there. Yamaha's MFC1 MIDI foot controller is an obvious candidate for this function, though the £225 tag might not make it a first choice for program selection if the REX50 is the only MIDI device getting the benefit of its versatility. The REX50's Memory footswitch input provides the second alternative; it's an easy way to step through a programmable series of effects and a cost-effective way around the non-MIDI blues.

Having got past the control side of program selection, how do the programs sound when you get to them? Well, the first impression the REX50 gives is that it is an SPX90-type programmable signal processor with guitar effects thrown in. This is pretty much the case, but there have been, of course, some compromises made to keep the REX50 at its £365 price level, and its controls familiar to guitarists. There are 30 basic effects which are permanently stored in programs 1-30. These basic programs do a good job of showing off the REX's basic features, but after working with it for a couple of hours, I found the need to store variations on these in the user-programmable memories, 31-90 - which are initially programmed with duplicates of the factory programs.

The REX50 generates its digital effects by digitising incoming audio into 16-bit words at a 31kHz sample rate, with a resultant 12kHz effects bandwidth. Since natural reverberation has little harmonic content over 10kHz, this limitation is not very drastic in the case of most of the REX50's effects, and in the cases where the effect bandwidth might be expected to be higher, such as the delay and modulation effects, the limitation can be masked to some degree by the dry signal.

What does all this mean? The REX50 sounds great. I tried it out both as an in-line effect with a couple of guitars, and as a stereo send on a portable four-track. In the case of one of the guitars, I found that turning the input trim pot up full did not provide enough gain to get the best signal-to-noise ratio, and "breathing" was detectable most of the time. Putting a preamp before the REX did away with this problem. On other guitars, I had no problem at all, and as an auxiliary send, it performed marvellously.

The Effects

THE SIX BASIC reverb types (hall, plate, vocal, room, early reflections, and gated) all sounded smooth when tested with guitars, drum machines and synths. I think that because the REX50 is designed with guitarists in mind, Yamaha have done a great job of making a wide variety of ambiences possible with very few variable parameters. The hall, room, vocal and plate programs provide variable reverb time, pre-delay, high frequency damping and high- and low-pass filter cutoff frequencies, and these did as good a job as you might expect for tailoring basic reverb effects.

"Given the option, I'd say that the R£X50's programmability is worth every extra penny, especially when it comes to delays and pitch shifts."

Not being a big fan of buckets of reverb on guitars, I found the Early Reflections and Gate reverb programs particularly useful for enhancing the guitar tone without being overpowering. Playing with the Room Size and Type parameters proved to be most effective.

Two basic stereo delay effects are included. The Stereo Echo effect produces two discrete delays with independent delay times and feedback settings. The Delay L&R effect is similar to the Stereo Echo in its controls, but the two delay signals are summed with the input for feedback, thus producing interactive delays. For example, a short left delay can be imposed on a long right delay, something which I found worked very well when combined with volume pedal work. In the case of the Stereo Echo program, I found the lack of a monophonic output a limitation, but the L&R configuration went some way towards compensating for this.

The flange, chorus, phasing, and now-famous Symphonic effects are enough in themselves to make the REX a desirable package. They sound clean and add a reliable shimmer to just about anything you put through them. Great stuff.

Like most low-cost pitch shifters, the REX50 has its glitches, but given the option, it earns its keep when shifting small intervals for thickening effects. As with the SPX90, MIDI Note On messages can perform real-time control of the two separate pitch shifts, making it fair game for sequencer control.

The distortion effect on its own is very usable, and provides control over the distortion amount, midrange frequency and boost, treble boost, trigger level and release time. These last two controls help keep the REX50 quiet; when you're not playing. The EQ controls, however, are a real pleasure to have on hand. Distortion can also be combined with reverb, delay or modulation effects, but control is reduced to just the distortion amount.

The unit also has compression, gate and panning effects which perform well, but given the 12kHz bandwidth, these are not really the sort of effects that would compare to their analogue equivalents. It's nice to have around in any case. Owners of SPX90s might point out that the REX50 has no Freeze, Parametric EQ, or Delayed Vibrato effects, and they'd be right. But given the choice, I'd pick the distortion effect over these for guitar applications, so it's no real loss.

The one problem I had with the REX50 was in trying to get it to do everything. Not that it couldn't perform each task individually, but when I started using a volume pedal, I found myself wishing I could insert it between the distortion and reverb in order to get better signal-to-noise performance. But this is a digital signal processor, and there is no way to insert the analogue world between these two points. I suppose the obvious thing to do is use two REX50's - such a purchase would come out to little more than a single SPX90II. Something to think about...


I BELIEVE THAT in live performance situations a good number of guitarists will do just fine with the REX50 as the main effects device in their setup. In small recording setups, the REX50 could work wonders as an inexpensive jack of all trades, laying down good sounds on tape initially, and also spicing them up in the mixdown.

I know that non-programmable digital signal processors have offered a good selection of effects for relatively, small money but given the option, I'd say that programmability is worth every extra penny - especially when it comes to delays and pitch shifts. The REX50 lets you get in there and tweak to your heart's content with a mere handful of parameters. Even if it had no distortion effects, it would be worth the money, but it does, it sounds good, and I'll bet guitar effects will never be the same again.

Price £365

More from Yamaha, (Contact Details)

Also featuring gear in this article

Yamaha REX50
(SOS Feb 88)

Browse category: Studio/Rack FX > Yamaha

Previous Article in this issue

Black Magic

Next article in this issue

MIDI Basics

Publisher: Music Technology - 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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Music Technology - Oct 1987

Donated & scanned by: Mike Gorman

Gear in this article:

Studio/Rack FX > Yamaha > REX50

Gear Tags:

Digital FX

Review by Rick Davies

Previous article in this issue:

> Black Magic

Next article in this issue:

> MIDI Basics

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