Mark Jenkins reports on the latest addition to the popular Boss Micro Rack series of budget signal processors - the RPS-10 Digital Pitch Shifter/Delay.

As property becomes more and more expensive, investors find it increasingly difficult to afford large studio premises, and so smaller installations become the norm. Studio designers exert themselves to fit more and more equipment into smaller and smaller spaces, and prospective engineers over five feet in height find it difficult to get work. Eventually, the breed of tall engineers dies out, and by natural selection the studio engineer becomes a midget, capable of sliding into the smallest spaces, with two or more pairs of hands in order to adjust several controls at the same time. It is for this race of super-midget engineers that the Boss Micro Rack Series was designed.

Well, that's one theory. Another (and possibly the more likely) is that compact circuit board design has made it possible to fit effects into half a 19-inch unit, a format which is becoming increasingly more popular (viz Alesis MIDIVERB), particularly for smaller home-based studios. With the use of digital design, there's no loss of quality either - in fact, the Boss series out-performs much bulkier units designed only a couple of years ago.

You probably all know by now what the basic layout of a Micro Rack unit looks like. Just under nine inches wide, the units have grey metal bodies, controls on the front panel, and input/output sockets on the rear. They take an external 9-volt power supply but feature a Power Output socket so that one Boss power adaptor (such as the RPW-7) can be shared by several units.

There are also two alternative input sockets to be found on most models in the range - a jack and a phono - which make the Micro Rack units ideal for use either with Fostex and Portastudio designs (phono) or with more professional multitrack equipment (jack). This arrangement is duplicated for the outputs, whilst a switch selects -10dB or -20dB operating levels for optimum matching with your chosen set-up.

On the RPS-10 Pitch Shifter/Delay unit reviewed here, there are four more jack sockets located on the rear panel: Hold, which freezes the pitch shift and echo effects when controlled from a footswitch (a pity there's no equivalent for this control on the front panel); Effect On/Off, again for footswitch control and duplicated by a front panel button with LED; Tuner Out, which sends a signal from the Pitch controls out to a chromatic tuning device if desired; and Keyboard Control, which we'll examine in a moment.

Moving smartly around to the front panel of the RPS-10, we find a typical Micro Rack dual design. The controls are shared between pitch shift and digital delay functions, so although you won't find as much versatility as on a dedicated DDL or harmoniser, at least you're getting a choice of two types of effects for your money.

Next to the Effect On/Off button is the basic mode selector, a multiposition switch offering the following options:

Delay Range (25, 50, 100, 200, 400, 800 milliseconds, Invert)
Pitch Shift (A, B, Invert)

There are then two tuning controls for the shift function: Pitch (from —1 octave to +1 octave) and Fine (from Flat, xO.5, to Sharp, x1.0). The Feedback control which affects both modes is simply marked Min to Max, and the Mix control is from Direct to Effect with a click stop at the centre 1:1 position. The unit's power switch has a built-in LED.

APPLICATIONS

So what applications could be found for a pitch shifter in the average studio? Most obviously, there's the production of harmonies on vocal or even on instrumental lines, which is why Eventide grabbed the copyright on the name 'Harmonizer'. So the RPS-10 is akin to a harmoniser if you like, but lacks many of the more advanced features of Eventide models and even of the Ibanez Harmonics/Delay series, although these are both of course much more expensive.

Slight pitch shifts when mixed with the original unshifted signal will give thickening effects similar to using two oscillators instead of one on a synthesizer, or using a twelve-string guitar rather than a six-string. Vocals, again, can be thickened up without producing a distinct 'harmony' line.

If you do want distinct harmonies however, the RPS-10 should be able to provide the goods, although there's been no attempt to mark the control settings for common musical intervals such as a 3rd, 4th or 5th. You just have to find them by ear using the coarse Pitch and Fine tune controls. The quality of the pitch-shifted signal and its commendable lack of glitching (cyclical irregularities in the sound) are of paramount importance here, particularly if you whack up the Feedback control setting on a large pitch shift.

This can provide an unusual, rather over-the-top effect that turns simple musical lines into spacey arpeggios and generally makes everything sound as if it's been recorded for an episode of Dr Who. But, as with all other effects, this is just a question of the subtlety with which it's used.

Keyboard control of the pitch amount is possible over a range of a couple of octaves. Simply plug the audio output of any synth into the Keyboard Control socket, use a simple monophonic sound, and the degree of pitch shift is set by the note played over a range of C5 (523Hz) to C7 (2093Hz), with C6 (1046Hz) serving as the neutral, zero shift position. This is the most reliable way to obtain preset pitch intervals, overriding the front panel Pitch control, and although it's no substitute for a vocoder or voice box, it can help create some complex vocal tricks in real time.

The two Pitch Shift modes, A and B, differ slightly in the frequencies on which they're centred. In 'A' mode, the time delay involved is short and some low frequencies tend to take on a tremolo effect rather than being shifted. In the 'B' mode, the delay time is increased with the result that the shift is slightly more stable. The difference is subtle, but can be a problem-solver.

The Delay functions on the RPS-10 are pretty standard, giving a maximum 800ms echo with a (quoted) 15kHz frequency response. But the unusual factor shared by the Delay and Pitch Shift modes is the Invert function, which Boss describe as being similar to "a tape recorder's reverse playback effect". It sounds as if the echo is being read out backwards in sections, because the actual order of notes played remains the same. In Pitch Shift mode, the Invert position gives the most incredible effect the RPS-10 is capable of generating, namely a rising or falling echoed arpeggio on every note played - great for the ends of particularly doomy compositions!

The RPS-10's handbook gives a couple of useful example settings with exotic names such as 'Infinite Score Raising Sound', and even shows how to change the pitch of a whole piece of music, although that's being a little ambitious because, like most budget harmonisers, the RPS-10 doesn't give an amazing shifted signal. Mixed in with the original, it's fine for thickening and small intervals, but around a 5th or an octave shift the quality is degraded and the shifted sound becomes fairly gritty. Boss do have the advantage over other designs that glitching is kept to a minimum, but there is a certain kind of gritty distortion that's all too easily produced with this kind of unit.

On the more over-the-top effects this isn't so significant, and the RPS-10 is quite capable of making you sound like Prostetnik Vogon Jeltz from The Hitch-Hiker's Guide To The Galaxy standing at the bottom of a well. But how often do you need that kind of effect? The RPS-10 is also great for pretending that you're doing fractal synthesis for the Arts Council Contemporary Music Network using a mainframe computer at IRCAM, whereas in fact all you've got is a Casio and a Pitch Shifter.

CONCLUSION

The bottom line, as always, is cost, and if you're looking for pitch shifting effects in this price-bracket, there's little opposition. The delay functions of the RPS-10 are a bonus and are of pretty good quality, although there's no modulation oscillator so the unit won't double as a flanger as well. But despite unavoidable problems in the quality of the pure shifted sound, which are much less significant when mixed with the original, this unit is still a valuable addition to the Boss Micro Rack Series.

The Boss RPS-10 Digital Pitch Shifter/Delay costs £210.00

(Contact Details)