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Digitech Studio Quad

Digital Effects Processor By Paul White
Published February 1996

Digitech Studio Quad

Paul White tries to pigeonhole Digitech's new effects unit — but quickly discovers that it can mean different things to different users.

Just when it seems as though design engineers are being hard pushed to come up with any truly new effects, they start combining them — with an ingenuity which leads to considerable complexity. Digitech are well aware of this potential problem, which is why they built the Studio Quad.

Based around their latest S‑DISC processing technology, the Studio Quad is a four‑in, four‑out processor that can be configured in a number of ways. A few of the possible options are: two independent stereo‑in, stereo‑out processors, four mono‑in, stereo‑out processors, or a classic mono‑in, stereo‑out device. In fact, there are 12 preset effects configurations to choose from, each capable of combining up to four effects blocks, or 'Modules' in series, parallel or series‑parallel combinations. Further variation may be introduced by changing the way in which the four inputs route to these configurations.

The effects generated by the various Modules are listed in the 'Effects Modules' box, and you'll notice that these are divided into three categories, depending on how much of the Studio Quad's processing power they take up. If you choose from the 'Quarter Resource' effects, you can have up to four Modules at once; with 'Half Resource' effects you can use up to two blocks; while a 'Whole Resource' effect blows all of your firepower in a single effect. You can mix these blocks any way you like, just so long as the total doesn't come to more than one 'Resource'.

To make life for the inexperienced user as easy as possible without forfeiting flexibility, the effects modules used in the factory patches are available as presets. This means that if you like a quiet life, all you have to do is pick a configuration, and then slot in the effects of your choice. If, on the other hand, you like customising effects, you can edit the effects at parameter level to create your own variations. To get you started, there are 100 preset 'ready‑to‑go' effects patches, and if you find one that's close to something you need, it's a simple matter to make a few edits, then store it into one of the 100 user memories. The whole ethos behind the Studio Quad is that you can use the machine at any level of complexity you like.

On the technical front, the circuitry is based around 18‑bit A to D conversion, and 20‑bit D to A conversion at a sampling rate of 44.1kHz, yielding a 20kHz audio bandwidth. The resultant signal‑to‑noise ratio is better than 90dB. The S‑DISC chip used to create the effects is more powerful than its predecessor, so the effects should, in theory, sound better than ever — as well as being quieter.

The Interface

Whatever else, the Studio Quad's interface is visually distinctive — the large perspex buttons look like partly‑sucked glacier mints, with green lights inside! A large custom LCD window takes care of metering, and standard functions such as patch naming, parameter editing and so on, but it also includes a graphic representation (the, erm... Effects Routing Matrix) of how the chosen configuration is connected up. By stepping through the effects modules in the matrix, you can open them up for editing, or replace them with other modules. Thankfully, the number of buttons has been kept to a minimum, and these have dedicated functions for accessing the edit pages, setting the utility parameters, adjusting the input levels and Bypass. Values are changed using a chunky data entry wheel.

Because you can work entirely with presets if you want to, newcomers to effects programming needn't feel intimidated by the operating system.

On the rear panel are the four input and four output jacks, with a single +4dBV/‑10dBu level switching button, plus the usual complement of MIDI In, Out and Thru sockets. Power is courtesy of an external adaptor, and there's also a footswitch jack which accepts a standard momentary switch to activate the bypass mode. Alternatively, you can buy Digitech's optional FS300, three‑button switch which provides for patch increment, decrement and bypass. Because the Studio Quad can be four processors at once, the Bypass switch is designed to bypass only the effected signal, and leave the dry part of the signal working as originally routed.

In FX Edit mode, you can edit the effects modules used within the patch, as well as set up the Input mode and the Modifier module. The Input module allows you to choose how the four inputs are routed to the effects configuration you're using. The Studio Quad treats the input patching and the choice of configuration as separate items, in that you can change the default input routing arrangement for a configuration once it's loaded. As you scroll through the available options (which are different, depending on the configuration you have chosen), the on‑screen graphics change to show you where your virtual patch leads are going.

The Modifier module is the equivalent of the modulation system used in synths, and each program in the Studio Quad can be used with up to eight Modifier links, which allow things like LFOs, input signal loudness, MIDI controller data or MIDI aftertouch to be used to alter effects parameters in real time. When used with dynamic instruments such as guitar, playing intensity can be used to control such things as the detuning amount.


During performance, the Studio Quad is set to Program mode, with the data wheel used to select new patches. Alternatively, MIDI patch change information can be brought to bear in the usual way. Patches can be bypassed using either the Bypass button or an external footswitch, and all signal levels are set via the software.

To edit a patch, it's probably easiest to call up a patch that already uses the configuration you want, then substitute new FX Modules and make any changes to the input routing you feel necessary. All the factory patches use default Modules, so if you come across one that you think might be useful, you can load it wholesale from the Studio Quad's library into any patch you're editing — which is a real timesaver. There are two banks of default effects: Bank A comprises wet/dry signal mixes for in‑line applications, while Bank B contains wet‑only settings, with a high effect level for use in the aux loop of a mixing console.

Once you've settled on your configuration, choice of effects modules and sorted out which input jack feeds what, you can set about assigning parameters to Modifiers, for real‑time control. Finished patches can then be stored and named with up to 24 characters. When you come to use a patch, the Studio Quad can set up the input levels for you in a similar way to the Alesis Midiverb IV. Holding the In Levels button puts the machine into 'listen' mode, where it monitors the input for around eight seconds, before setting the input gain according to the loudest peak.

As is now almost mandatory, a MIDI assignment table can be set up, to map incoming MIDI program change numbers to any patch number. The memory of the Studio Quad may be dumped or reloaded via SysEx.

Studio Test

Though there are no brand‑new effects in this box, the various ways in which you can combine them provides access to a very wide range of textures. As always, many of the subtleties are lost in a busy mix, but for new age music or other types of sparse composition, you can create effects with a lot of detail. Delay times can be entered directly by tapping a front panel button, and in the case of the multitapped delays, the delay and level can be set independently for each tap.

Though the pitch shifter still has the artificial shimmer characteristic of all affordable effects units, the dissonant beating effect is far less pronounced than on many other FX boxes I've tried. Provided the shifted signal isn't expected to stand scrutiny on its own, it works quite well. All the modulation effects create a rich sense of movement, and with a choice of four LFO waveshapes, you can create chorus and flange effects with a range of characters.

When it comes to reverb, the processor‑intensive Dual Stereo reverb offers the most editability, with 17 user‑adjustable parameters, while your basic 'cooking' reverb has only eight. I actually like the sound of Digitech reverb algorithms. They don't ring unless they're supposed to, are nice and dense, and create the impression of a real, three‑dimensional space. Having an automated input level facility really helps out if you're one of those people who think that gain structure is something to do with pension schemes, and providing you set the levels properly, the Studio Quad is as quiet as most other effects processors in its class. Inevitably, the flange effects and any other patches relying on large amounts of feedback are noisier than the straight delays and reverbs, but if you use them with care, this isn't a problem.


It's sometimes hard to keep in mind that the Studio Quad is actually a budget unit, and you can easily pay out more money for a far less powerful box. The limitations are less to do with sound quality than how many effects you can combine before you run out of processing power — but then I'd take three or four good effects against 20 indifferent ones any day.

With most effects processors, you can see exactly which part of the market they're aimed at, but the way in which the Studio Quad is priced and designed makes it much more difficult to pin down. Because you can work entirely with presets if you want to, newcomers to effects programming needn't feel intimidated by the operating system, and even when you get more adventurous, you can still proceed cautiously, by slotting different effects Modules into different configurations to see what happens.

Those who already have experience in programming effects and who like to edit at the deepest level will find plenty of opportunity to ply their art, and the more experience you have, the better the feel you get for what effects work best in which order. Perhaps the best way to sum up the Studio Quad is as the 'Burger King' of effects units: if you want four simple studio effects in one box, you've got it; if you want almost instant gratification when it comes to editing effects, you've got it; and if you want to concentrate all the unit's power to give you one big studio‑quality stereo reverb, you've got that too. The Studio Quad is an effects unit that virtually anyone can make use of straight away, yet it'll take a long time to grow out of. Digitech definitely have the right idea.


Because the four inputs and outputs are configurable in so many ways, the Studio Quad can be used in lots of different situations. In the studio, it can take the place of up to four conventional effects boxes with each input connected to its own aux send. The simplest way to do this is to route all four Module outputs to output jacks one and two, so that your stereo effects mix only takes up a single stereo return on your mixer. Of course you could split them to two stereo returns if you wanted.

The opposite extreme is to feed all four Modules from a single input, and then route these to the four outputs to provide quadraphonic effects for live performances. This requires a four‑speaker, four‑amplifier PA, but the results can be worth the effort. Other studio options include creating your own stereo effects where the right hand output is processed via different effects modules to the left, which is an easy way of creating very dramatic stereo effects. For conventional studio use where you want to use all the processing power to effect a single signal, a setup with one input and a stereo output covers most eventualities.

More About FX

As explained earlier, the effects are divided into groups according to how much processing power they require, and as a rule, the longer delays and most complex reverbs take the most horsepower. The simpler reverbs have fewer parameters to adjust and may be less dense than the high‑powered versions, but in the context of a composite effect, they don't show up as lacking in any area.

Having the ability to decide which effect goes where within a configuration is actually very flexible, because there's quite a difference between a flanged reverb and a reverbed flange. As you can see in the 'Effects Modules' box, the Studio Quad delivers all the usual delay and modulation effects as well as reverb and four‑octave pitch shifting. On top of that, there are several EQ options, from small parametrics to huge graphics, and to help keep everything quiet, there's a noise gate module too.


  • Can be used on a variety of levels depending on how much editing you like to do.
  • Good algorithms, particularly the reverb.
  • Can be configured as up to four separate effects processors at once.


  • The maximum number of effects that can be combined is four, but the processor‑intensive nature of some of the effects modules will reduce this number.


The Studio Quad represents a serious attempt to build a user‑friendly effects processor that won't become redundant as your requirements get more sophisticated.


£499.95; FS300 footswitch £49.95. Prices include VAT.

Published February 1996