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Digitech S100

Dual-engine Multi-effects Processor By Hugh Robjohns
Published April 1998

Digitech S100

The S100 offers half the innards of Digitech's Studio Quad, but sells for half the Quad's price. Hugh Robjohns finds out whether it does everything by halves...

The newest in Digitech's well‑regarded family of digital signal processors is the S100 multi‑effects unit, effectively a simplified version of the Studio Quad (reviewed SOS February 1996; Version 2 reviewed September 1997) that uses two processor modules instead of the former's four. The S100 certainly looks very attractive, with its extruded blue front panel, but has it been built to meet a price rather than to excel on the range and quality of effects?

What's In The Box

Much like the updated Studio Quad, the S100 offers a comprehensive signal‑processing package made all the more flexible through five different DSP configurations of its "dual‑engine processing power". Two DSP modules can be combined to provide a single, powerful stereo signal effect (C1), or arranged as different effects modules connected in series (C2) or in parallel (C3). The DSP power can also be configured to apply completely independent processing on the two signal channels (C4), or the two processes can have separate inputs but combined stereo outputs (C5).

In C1 mode (the single‑processor option), the algorithms have access to the full processing power of the DSP engine, so maximum delay times are longer than with any of the other modes, and the reverb programs have far more dense and realistic decay structures.


Digitech's new S100 is certainly up to scratch in terms of its audio specifications. Although the machine operates at the rather bizarre sampling rate of 46.875 kHz, this does mean that it has a full audio bandwidth of 20Hz‑20kHz. I don't know why the converters run at this peculiar rate, but since the S100 doesn't have digital audio inputs or outputs, the internal sampling rate is of no real consequence. The A‑D converters are conventional 20‑bit, 128x oversampling types, and all the internal digital data busses and DSP calculations run at 24‑bit resolution. As you'd expect in this day and age, the S100 supports the usual MIDI program change commands and also has rear‑panel facilities for footswitch‑operated program changes and effects bypass. The program memory offers 99 user locations and 99 factory programs.

The S100 lives up to its 'multi‑effects' title — the factory presets include a wide variety of reverbs, delays, modulation effects (such as flanging, phasing, chorus, tremolo, panners, and Leslie simulators), plus some far more esoteric programs such as vocoders and ring‑modulator effects. There's also a range of combination and split channel multi‑effects which should take care of pretty much every requirement.


The S100 is a conventional 1U rackmount unit with a 9V AC external PSU. I'm not a fan of these, but the practicalities of manufacturing units to meet the various EMC laws around the world make this approach increasingly common.

On the extreme left of the back panel, there's an uncalibrated input volume control, of the kind that you generally set once and forget. There are many circumstances when this will be perfectly adequate (such as when the unit is connected to a mixing console's aux send), but should you have to adjust input gain occasionally, this arrangement does make things rather awkward, especially if the unit is mounted in a rack.

There are four quarter‑inch sockets for the two inputs and two outputs. The left socket of each pair is marked for mono usage, and they're wired for unbalanced operation, with a sensible headroom of +18dBu. Further to the right, after the coaxial power socket, there's a quarter‑inch footswitch jack, and finally a MIDI In.

Controls & Operation

The S100's front panel is very clean looking, and the controls are reasonably intuitive to operate. A row of 12 push‑buttons is arranged beneath a multi‑function display, with a relatively large data‑input wheel to the right. Unfortunately the printed legends on the push buttons are not engraved, and I fear they may fade away with use — which could make operating the unit rather challenging! Also, on the review model the legends were not all printed squarely on the buttons, which rather detracted from the otherwise professional appearance of the unit. There are secondary legends printed beneath the push‑buttons, and if the unit was mounted reasonably high in a rack these would be legible, but if you were looking down towards the S100 these legends would be obscured by the buttons and extrusion. This is a shame, as they provide a useful aide memoire as to which reverb functions are assigned to which parameter buttons, as well as identifying the buttons associated with program editing functions.

As I've already said, the S100 is fairly straightforward to use — although the program code letters can be rather confusing at first (see 'Display's The Thing' box), a combination of trial and error, with some careful listening, quickly establishes what's going on. The user manual is pretty good at pointing out less obvious facilities, and at only 20 pages it's not too daunting to flip through before playing with the machine.

The key operating buttons tend to be those in the right‑hand half of the row, with the customisation and configuration buttons in the left half. The first three buttons (Program, Store, and Config) are reasonably self‑explanatory: Program steps the machine through the program memories (as well as restoring normal program operation after editing); Store allows a user‑modified algorithm to be saved; and Config selects one of of the five dual‑engine configurations.

The next button is labelled Mix/MIDI, and this allows you to turn the dry signal path through the machine on or off, and to set the MIDI data receive channel for program change information. For anyone in any doubt, the dry signal path would generally be left turned on if the S100 is being used as a stand‑alone signal processor with a guitar or keyboard, but should be turned off when the unit is connected to the auxiliary send of a mixer. Even when the dry path is selected, it's automatically disabled in certain effects programs, including tremolo, panning, vocoder, compressor, Leslie simulations and reverse reverberation effects, where the processed sound is all that's required.

The MIDI implementation is basic but appropriate to the functionality of the machine and is centred around program change instructions. Program numbers 103 and 104 select user and factory program banks respectively, with program numbers 1‑99 corresponding to the relevant stored programmes in the S100. Program change numbers 100 and 101 apply or cancel bypass, and 102 simply toggles the bypass on and off alternately. The dry signal path can also be controlled via MIDI Continuous Controller 7.

The last button in the configuration section gives access to an EQ/Gate facility which applies to the signal path for all effects processing.The equaliser is a 3‑band affair with top and bottom shelf responses controllable only in level (+/‑ 12dB). These are supplemented with a parametric mid‑band section offering the same boost/cut range with adjustable centre frequency. Unfortunately, the frequency parameter is numerated from 1 to 26, which is not particularly useful, although your ears should be able to tell you when you've found the frequency you're looking for!

If the EQ/Gate button is pressed twice, the noise gate can be set up through simple Release and Threshold parameters. Again, the parameter values are arbitary, with threshold ranging from 99 to zero, plus off, and release from 1 to 10. Nevertheless, this is a useful facility, particularly if you're using the S100 in stand‑alone mode with some of the noisier keyboards. As with all noise gates, great care is necessary in fine‑tuning the parameters for the least intrusive operation.

Six of the remaining seven buttons are used for detailed parameter editing, with the last providing a bypass facility. Each of the two processing engines can be addressed separately through a pair of buttons labelled, not surprisingly, Engine A and Engine B (only Engine A operates in the combined single‑processor C1 mode). Once the appropriate engine is selected, the desired effect algorithm can be dialed up with the data‑entry wheel and the relevant parameters modified to taste by pressing one of the four parameter buttons and spinning the data wheel once more.

This is where the manual becomes indispensable, as not all the two‑letter codes representing the different effects programmes and their adjustable parameters are entirely obvious — Cfor chorus and Ch for chamber reverb, for example. As I mentioned earlier, there are additional legends on the front panel to identify the adjustable parameters associated with the reverb programs (pre‑delay, decay, damping (HF decay), and level), but not for the other effects algorithms. Even in reverb mode, not all programs have a damping parameter — the gated and reverse effects replace this with diffusion.

In general, the effect programs are provided with a predictable but sensible selection of up to four adjustable parameters, and the range of adaptation is wholly usable throughout. I would have felt more comfortable if some of the parameter values were specific rather than arbitrary, although this probably says far more about my audio engineering upbringing than about the usability of the Digitech S100.


As you'd predict from its price of well under £200, the S100 has been specifically targeted at the home rather than the professional studio — not that there's anything wrong in that, of course. The range of effects provided, and their overall audio quality, while being of a reasonably high standard, seems to me to be orientated towards synth‑based music, particularly techno styles, more than anything else. The characteristic sound of the reverb algorithms, which tends to be on the 'metallic' side, suits hi‑tech music very well, but in more demanding situations I often found the reverb algorithms lacking in subtlety and realism — for example, I got the impression that there was quite a lot of Formica in the 'Wood Recording Studio' program!

Some of the other effects are fun, though probably of relatively limited usefulness. The Vocoder mode has five different preset sounds which, although distinctive, would have to be used sparingly, and the same is undoubtedly true of the ring modulator.This could be used to great effect in the right place, but it seems to be more gimmicky than really useful.

The Leslie speaker simulator is more impressive and has a useful range of adjustability, though — understandably — it's not as good as some of the specialised units now available. The main time‑delay effects, such as chorus, flanging, phasing, tremolo and straight delays, are all fine, but these are the easiest of routines to program, after all. The pitch‑shifting and detuning options fare rather less well. Although tolerable on simple sound sources, when applied to voices, even the smallest pitch‑shifts sound mechanical, and larger shifts become comical sooner than they really should. To be fair, pitch‑shifting is extremely difficult to do well, and the best boxes are all very expensive.


Having spent some time playing with the S100, I would have to say that it doesn't offer anything very new, and you also need a photographic memory or some good lateral thinking to figure out the hieroglyphics in the editing displays. However, the sound quality is perfectly adequate for many applications, and it does offer a decent variety of treatments for the price.

If I had to use one word to describe the overall character of the S100 I would say 'brash'. If brash is what your music needs — and much in the dance line seems to want as 'dirty' and aggressive a sound as possible at the moment — this box could be what you're looking for.

In all fairness you'd probably have to pay double to get a unit with much more realistic reverbs — the Yamaha REV500, for example. Although the DSP configuration options in the S100 allow it to do a few things some other budget processors can't, I don't think I would be tempted to replace one of my older units with the S100. On the other hand, if you're looking for your first multi‑effects processor, this one does everything reasonably well for the money.

Display's The Thing

The S100's display is divided into three zones. A large, 2‑digit, 7‑segment LED is positioned to the right, with two collections of LED indicators on the left‑hand side. The first block tells you which of the five 'Engine Configurations' is selected. The display shows simple block diagram graphics of the five arrangements, with LEDs to reveal the current mode.

The centre block shows a multi‑function LED bargraph input meter, scaled from ‑18dB to 0dB(FS), in 6dB steps. This provides a guide for setting the rear‑panel input‑level control. However, when the machine is in 'Edit Mode' and program parameters are being altered, the two LED columns indicate which kind of algorithm each processing engine is running: Mod/Pitch, Delay, Reverb, or Other.

Normally, the 7‑segment LED displays the current program number (1‑99), and a 'full stop' in the bottom right‑hand corner differentiates between the factory programs and the user memories (illuminated for user programs). However, in Edit mode the display also indicates the selected effect and parameter with 2‑character alphanumeric codes. When a parameter is adjusted, the display also shows its value, although these are frequently arbitrary numbers rather than anything directly meaningful.

The abbreviations for program algorithms can be obtuse, and I found it essential to use the S100's manual. This actually states that a table of effect names and their parameter codes is printed on the top of the machine but this wasn't the case on the review model. I would have found this very useful while I was getting used to the machine, although if the unit is rackmounted, such labelling becomes rather pointless.


  • Looks good.
  • Flexible configuration options.
  • Wide range of effects and reverb programmes.


  • Brash sound quality
  • Average program algorithm quality.
  • Obscure 2‑character display abbreviations.


Attractive general‑purpose multi‑effects processor with some intriguing programs but offering nothing revolutionary or outstanding.