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Digitech Studio 400

Effects Processor By Derek Johnson
Published October 1996

Though it costs no more than last year's TSR24S, Digitech's latest top‑line studio processor offers twice the power, an improved user interface, and a digital connections option. Derek Johnson leaps into action.

It's now an established fact that anything based on digital technology has an evolutionary pattern that means you get more — often a lot more — for your money with each successive generation. It's true for PCs, it's true for sample‑based synths, and it's true for digital multi‑effects. This fact came particularly into focus for me with the release, in 1995, of Digitech's TSR24S, an enhanced version of their 1993‑vintage TSR24, offering a better feature set for £100 less than the original. Most attractively, it also offered expandability — an extra couple of hundred pounds added a board that essentially doubled its processing power.

Now we're getting towards the end of 1996, and there's yet another generation of Digitech to examine. At first look, it's certainly fitting in with the trend, offering the power of two S‑DISC (Static/Dynamic Instruction Set Computer) processors — as opposed to the TSR24S's one — for the same price as the latter unit, £799. There's more too: a host of new effects, and extra features such as four sets of inputs and outputs, on both balanced jacks and XLRs. That added processor power gives the Studio 400 the ability to behave as up to four separate multi‑effects processors at once, utilising a maximum of eight effects simultaneously (the cheaper Digitech Studio Quad, reviewed back in February, also manages four independent processors, but with a maximum of four effects at a time). The 400 can be used as a single super‑processor, as four separate processors (patched into four auxiliary sends of a mixer), in‑line with a stereo synth, or any combination of these. The choice is yours. It can also be upgraded to include digital connections, should you require them.

One of the really excellent features offered by the TSR24/TSR24S was the ability to freely create custom effects algorithms; this is missing from the new unit, Digitech instead choosing to provide a collection of preset 'Configurations' that almost approach this ideal — but I'm jumping ahead of myself.

Look & Feel

In order to cram in a serious collection of connectors — eight XLRs and eight jack sockets require a certain amount of space for comfortable use — and to make room for the optional digital interface board, Digitech have chosen to package their new baby in a 2U‑high box. This gives the Studio 400 a solid, imposing feel. Cosmetically, it reminds one of an older generation of rock‑solid professional studio processors that cost many pesos more than this one. It also looks a little square, for my taste anyway. But looks aren't everything when it comes to signal processing — and inside the Studio 400 is a throbbing effects‑processing powerhouse.

Upon switching on, your eye is quickly caught by the large, custom, backlit liquid crystal display. It immediately gives the appearance of being immensely informative, and so it proves to be. System navigation is undertaken by a small collection of large buttons and a big parameter‑access knob, which offers a reassuring click every time you move it. This is a change from the multitude of buttons found on the TSR units, and is a similar approach to the Studio Quad's.

If proof was needed that Digitech are a force to be reckoned with in affordable digital effects, the Studio 400 is it.

The 400 fires up in Program mode, wherein the chunky knob selects from the 191 preset Factory and 100 User Programs (the 100 User Programs are initially filled with duplicates of the first 100 presets). As you scroll through the Programs, you notice a number of things about the display, most significantly the miniature routing graphic in the lower right‑hand corner — it shows you exactly how the various effects components are linked together. Excellent.

Editing a Program is simply a matter of hitting the FX Edit button to cycle through each of the effects (up to eight) in a Program, plus a few routing parameters. You then access the editing parameters for the effect you want to edit, using the Previous and Next Page buttons; these cycle through the several pages available (there can be up to 10) for each effect. Each page features up to four parameters, and these are selected via the four soft keys, labelled 1‑4, in the middle of the button field. This is an odd place to put these keys, given that they would more sensibly be situated under the display — it's not as though there's no room there.

The remaining buttons are pretty self‑explanatory: press the Store button when you're happy with an edit, and would like to name it and save it in a User Program position; press the Utility button to access a range of global functions, such as display contrast, MIDI channel, and SysEx dump; and use the Bypass button to turn the effects off. Finally, the In Levels button allows you to manually set an input level, or tell the Studio 400 to 'intelligently' choose the optimum level for you.

The back panel is almost more interesting than the front, for a change. In addition to the sea of balanced audio connectors, there's a switch that chooses between +4dB and ‑10dB (pro or line‑level) operation, a pair of MIDI sockets, and a footswitch socket. As mentioned, one thing you do not get for the money — but which is available as an option — is a set of digital connections.

Inside Story

Those of you familiar with Digitech products will be on fairly safe ground here, because although the Studio 400 is in many ways the most powerful processor yet made by the company, they have stuck to familiar ground when it comes to effects and routing. Accessing those effects is, however, a little different. The effects hierarchy can be tricky to get into at first, and is trickier to describe. This is one point where the manual lets the user down — the explanations are all over the place.

The heart of each Program is a so‑called Configuration, one of 23 preset arrangements of 1‑8 effects 'Modules', arranged in a simple chain, or in several parallel paths. The Modules are individual effects, and it's for you to decide which ones you want in a Configuration — as long as you stick to certain rules. A Configuration isn't the end of the routing story, since there are several input/output modes — from single or dual mono, to stereo and quad mono input — with a similar collection of output modes. Not all options are available (or would be valid) for every Configuration, but they do help to stretch the preset nature of the Configurations.

The flexibility continues with the individual effect Modules. There are 50 altogether (plus bypass and through Modules), offering a variety of graphic and parametric EQs, compressors, delays, reverbs, flangers, and so on. And the choice doesn't stop there. When assembling custom algorithms with the TRS24S, it was necessary to keep juggling available processor power and RAM, choosing from a collection of effects Modules of varying power. This process is essentially invisible on the Studio 400. It works like this: Configurations make use of three different types of Module — full‑, half‑, or quarter‑power (just like the Studio Quad). This means that many of the 50 available Modules come in full‑, half‑, or quarter‑power versions, with differences in the range or variety of their parameters. A delay may have a longer or shorter delay time depending on what 'power' it is, for example. Some effects, such as the processor‑hungry Dual Stereo Reverb and Stereo Quad Delay, are understandably available only in full‑power versions.

Since Configurations are composed of slots which are pre‑defined for certain Module types, you can't just shove in any Module type you want — if the Configuration is for eight quarter‑power Modules, you can only use quarter‑power Modules. So choose a Configuration with a collection of Module types that best suits your needs, and refer to the charts in the manual to see if a given effect is available in the desired power. The maximum available power adds up to two full‑power effects, which means a maximum of four half‑power or eight quarter‑power effects, with loads of variations in between — one full, one half and two quarter, for example, would equal two full‑power effects.

That's just about it, except that once you've slotted a Module into position in a Configuration, there are some more decisions to be made. Digitech have provided each effect with a collection of 'Defaults' — sets of parameters that give you good starting points for your own experimentation. All Factory Programs use these Defaults, so if you hear something you like and want to use in the Factory Programs, you can easily figure out which Default is being used and copy it to your own Program. Note that there are two banks of Defaults; Bank A is suitable for in‑line applications, while Bank B is suitable for use with a mixer's auxiliary send loop.

Some of the Studio 400's reverbs have one further level of choice: a Type parameter allows you to choose from one of 10 different reverb types (Studio Room; Wood Room; Vocal Plate; Concert Hall; Plate Reverb; Chamber; Cathedral; Arena; Cement Shelter; or Infinite Spring), each of which offers a different decay range. Gated reverbs also have a choice, of 12 Types in this case. Matters are further confused by a pair of dual‑effect Modules (chorus/delay and flange/delay), which are available in full, medium and economical versions — so when we say the Studio 400 can use a maximum of eight effects Modules, any or all of those Modules could be made up of a dual effect.

Easier to explain is the way in which up to eight parameters per effect can be controlled by 'Modifier' links. A Modifier can be a MIDI Continuous Controller, one of two LFOs (Low Frequency Oscillators), or 'Dynamic' Modifiers. This latter choice uses the level of the input signal to control the assigned parameter — the decay time of a reverb could change depending on the level of the input signal, for example.

In addition to the eight MIDI controllers that can be assigned to each Program, the Studio 400 offers a full MIDI spec: patches can be changed remotely, and the unit's memory contents can be dumped or retrieved via System Exclusive. It is also possible to fully edit the 400 using an external SysEx editor, although details weren't provided with the review unit — full SysEx data is available in a separate document.

The Effects

Describing the operation of the Studio 400 is not quite as easy as using it. A little breaking‑in period may be necessary for some, since the display, while generally clear, does contain some tiny text, and moving about the system with the FX Edit, Parameter and Page buttons may be initially confusing.

Once you're past this, and diving into the treatments offered by the 400, you'll be glad you persevered. Just running through the Factory Programs gives you an idea of what the unit is capable of — anything from big, realistic reverbs to outlandish, swirly textures come pouring out. Unfortunately, the manual declines to actually describe what the designers were after when developing the different effects Modules for the Studio 400, so this period of testing the water will help you familiarise yourself with what's available.

For some people, a multi‑effects processor lives or dies on the quality of its reverb. The Studio 400's reverb algorithms have a natural feel to them that doesn't colour the input signal in an unpleasant manner, with none of the metallic edge detected on many cheaper units. Springiness and coarseness are also generally absent, which is good news for drum machine users. As for vocals, in my opinion it doesn't get any better than this until you start shopping in the £1500+ price bracket. Even the half‑ and quarter‑power reverb Modules offer a feeling of quality and space.

Other effects are also of a high quality: the long delays are eerily exact copies of the input signal, flanges and choruses are rich and full, and the rotary speaker simulator is a welcome bonus. Pitch‑shifting is also available in several interesting flavours, and is rather less crunchy than you'd normally expect from an affordable processor. It's still not up there with Eventide, but it's as close as most of us will get — as you'd expect, perhaps, given Digitech's acclaimed range of pitch‑shifter/harmoniser machines. Most interesting is the Harmony effect, which provides harmonies depending on what key you're playing in.

In combination, the effects get even better: flanged reverbs, reverbed delays, autopanned pitch‑shifting, and much more, are all possible, and sound excellent. Amongst the Factory Programs, I found a number of favourites: '20 So Many Effects' produces a wonderful melange of sound, no matter what the input signal; '81 Centerless Delay' and '82 Centerless Reverb' both offer a similar feeling of space without drowning the input signal or providing any clues as to where the effect is coming from — it just washes around the speakers; '173 Stereo Big Cathedral' seems to go on for ever; and '21 Leslified Room' gives you vertigo. An excellent set all round.

The Bad Stuff

There is so much that is good about the Studio 400 that it seems a shame to point out any shortcomings. Luckily, they are few, relatively insignificant, and mostly in the 'missing' category. The Studio 400 lacks: a headphone socket; a sampler (a hold function on some delays is as close as you get); and front‑panel input or output level controls. I found the contrast control for the LCD didn't have enough range — it's tricky to adjust it to be readable from all angles, and I missed true algorithm creation slightly — though the variety of Configurations and flexible input/output options amount to just about the same thing. The user gets last say on which effects Modules go where, after all.


While I wouldn't necessarily sell my house and all its contents in order to obtain a Studio 400, I might consider thinning out my effects rack to make a little spatial and financial room for it. And that's something I haven't been seriously tempted to do for quite some time by an effects unit. Some of you may find just under £800 to be a bit steep when you can take your pick of sub‑£400 processors. However, if you think of the Studio 400 as four processors in a box — if you've got four auxiliary sends on your mixer, the 400 will take them — that works out as £200 per processor, which is pretty good going.

Digitech have been producing fine effects units for years, and the Studio 400 is arguably their best and most powerful studio‑biased box yet. I can't recommend it highly enough. If proof was needed that Digitech are a force to be reckoned with in affordable digital effects, the 400 is it. There is little in this price range that offers such a range of exciting, musical and natural reverbs alongside potentially outlandish and unreal effects. The balanced XLR connectors may well cause pros in search of something different to check it out, and home and semi‑pro studios should definitely pay attention. If your budget can stretch to anywhere near the £800 asking price, you owe it to yourself to have a listen.

Digital Options

It is possible, for £199.95, to add full digital connections to the Studio 400. The interface is user‑installable, and allows the 400 to process entirely in the digital domain, providing you have suitable hardware (a digital desk, for example) with digital ins and outs. The board offers both XLR AES/EBU connections and S/PDIF phono sockets — you can switch between the two formats, but not convert between them. Sample rate is selectable, using a switch in the Utilities Menu on the 400, and the unit will automatically sync to external sample rates.


  • 18‑bit, 128x oversampled ADC
  • 20‑bit, 64x oversampled DAC.
  • 44.1kHz sampling frequency.
  • Balanced jack and XLR connectors.
  • MIDI In and Out/Thru.
  • Operating level switchable ‑10dBV/ +4dBu.
  • 20Hz‑20kHz frequency response.
  • 191 Factory Programs, 100 User Programs.

Those Effects In Full

This is a list of all the effects Modules available on the Studio 400; not all are accessible in all Configurations, and some are available in various 'strengths'.

  • REVERBS: Reverb, stereo reverb, dual reverb, stereo dual reverb, gated reverb, stereo gated reverb, room echo.
  • CHORUS: Dual chorus, stereo dual chorus, quad chorus, octal chorus.
  • FLANGERS: Dual flange, stereo flange.
  • PHASERS: Dual phase, stereo phase.
  • OTHER MODULATION EFFECTS: Rotary speaker simulator, stereo tremolo, auto panner.
  • DETUNING: Detune, dual detune, stereo dual detune, quad detune, octal detune.
  • PITCH‑SHIFTER: Dual pitch, stereo pitch, stereo dual pitch, quad pitch, octal pitch, smooth pitch, harmony.
  • DELAYS: Mono delay, dual delay, quad delay, stereo delay, stereo dual delay, stereo quad delay, analogue delay, stereo analogue delay, pre delay.
  • EQUALISERS: Mono PEQ6 (Parametric), stereo PEQ3, Stereo PEQ6, mono GEQ8 (Graphic), stereo GEQ8, mono GEQ15, stereo GEQ15, mono GEQ31.
  • SIGNAL PROCESSING: Noise gate, compressor.
  • DUAL EFFECTS: Chorus/delay, flange/delay.


  • Four independent effect processors.
  • Up to eight effects available at once.
  • Balanced XLR connectors.
  • Imaginative presets, classy sound.
  • Versatile.
  • Digital connections option.


  • Operating system may confuse some, and the manual doesn't help much..
  • Otherwise useful display has some rather small text.


A high‑class processor at a mid‑market price. Highly recommended, because of its flexibility and sound quality, for serious project studio owners and professionals.