Since the mid 1990s, BOSS’ GT-series processors have set the standard for floor-based multi-effects for guitarists, offering amazing COSM amp tones, a diverse range of great effects, and exceptional real-time control. I’ve personally owned every GT processor since the first (the GT-5), and have enjoyed their excellent sound for both studio and stage work. But when I recently plugged into the new GT-100 Amp Effects Processor for the first time, I realized that it was in a different league from previous generations, and a serious step up in tone quality. And that’s saying quite a lot, because the GT-series rigs have always sounded fantastic.

Powered by a new ultra-high-speed DSP chip developed by BOSS, the GT-100 delivers amp tones that truly sound and feel like the real deal, with presence, fatness, and sweet dynamic response that really inspires. The GT-100 is also loaded with a ton of effects, of course, and they benefit from the enhanced DSP as well. On top of that, BOSS has made the GT-100 the most intuitive and easiest-to-use multi-effects yet, making it simpler than ever to dial up great tones on the fly. There are many other cool features, too, such as the dynamic new ACCEL group of effects, an enhanced Manual (stompbox) mode, a looper, and many others. Sound interesting? Let’s take a closer look at this amazing tone monster.

Beauty and Brains

The GT-100 is built with a heavy-duty, all-metal chassis that’s ready to withstand years of hardcore stage use. It has a sleek black finish, eight footswitches for selecting patches and controlling various functions, and a rock-solid integrated expression pedal (with toe switch) for volume, wah, and other foot-controlled effects. But the centerpiece of the unit is its unique user interface, which features two LCD or two large displays and eight knobs for tweaking settings. This setup makes the GT-100 incredibly easy to navigate; I’ll tell you about it in greater detail a little later in the article.

On the rear panel, you’ll find a host of connectivity, including a standard guitar input, 3/4-inch mono/stereo outputs, a PHONES jack, an effects loop, and an AUX IN jack for connecting an external music player for practice and jamming. There’s also an amp control jack for using the GT-100 to switch channels on your amp, and a SUB CTL/EXP jack for connecting up to two external footswitches (such as the FS-5U or FS-6) or an expression pedal (EV-5 or FV-500H/-L) for additional control. MIDI I/O is also included, as well as a USB jack for connecting to a computer for audio streaming with a DAW and backing up patches with the GT-100 Librarian software.

The under-the-hood secret behind the GT-100’s incredible tone is the ESC2 DSP, a super-powerful digital signal processor developed by BOSS. Unlike the off-the-shelf chips used in competing gear, the ESC2 was built specifically for music applications—and COSM algorithms in particular—allowing BOSS engineers to leverage its power in ways that would be impossible with ready-made processors. ESC2 is also incredibly speedy, delivering a sixfold performance increase over the processors used in previous generations.

New and Updated COSM Amps

For the ESC2-powered GT-100, BOSS has developed a group of all-new “Advanced” amps. Instead of replicating specific amps of the past, the Advanced amps employ BOSS’ years of research in analyzing the unique tone and behavior characteristics of vintage classics to create a series of original “super amps.” In concept, this approach is similar to the way modern “boutique” amp designers combine the best concepts from the past with new tweaks to create their own unique amps. In the Advanced category, the GT-100 gives you eight different BOSS boutique models, ranging from sweet clean amps to insane, over-the-top metal machines and everything in-between.

BOSS has also completely revamped and updated its library of classic COSM amps for the GT-100. This “Vintage” category includes amps found in previous GT processors, such as the venerable Roland JC-120, American tweed, blackface, and high-gain amps, Brit combos and stacks, and more. What’s different is that they’ve been tweaked to take full advantage of the ESC2’s power, taking the already great-sounding previous models up quite a few notches in tone quality. The COSM amp section also features a Custom model, with special parameters that allow you to build your own amp with a tonal character just how you like it.

The GT-100 has a parallel signal path that lets you combine two amp tones together, or switch between them in a patch. Separate effects can even be used with each amp if you like. You can use a footswitch to toggle between the amp tones, of course, but the GT-100 offers two other unique ways to switch amp tones that unlock a world of real-time tonal versatility. One way is with picking dynamics, where one amp plays when you pick softly, and another plays when you pick hard. Another is via a specified frequency range, where you can have one amp play on the lower pitches and another on the higher pitches.

In a word, all the amps in the GT-100 are stunning. Not only do they sound excellent, but they feel great as well, delivering an organic, dynamic experience similar to playing a classic tube amp. The tone is complex and satisfying in ways that you simply haven’t heard before in a digital amp processor, either hardware or software. I could go on, but you really need to plug in and try it for yourself—I don’t think you’ll be disappointed.

Visit the GT-100 Tone Room.

Loaded with World-Class Effects

The GT series is renowned for its world-class BOSS effects, and the GT-100 is packed with a ton of them. You can freely change the order of effects as you like, and employ both serial and parallel processing paths for an enormous range of tonal possibilities.

There are essential effects such as compressor, overdrive/distortion, delay, chorus, and reverb, with a wide range of variations in each category. The overdrive/distortion group also features a number of Advanced variations introduced with the GT-100. These employ a similar design philosophy to the Advanced amp category, and utilize the power of ESC2 to its fullest. Additionally, there’s a Custom OD/DS effect for creating your own unique overdrive/distortion. Also onboard is an enormous array of specialized effects, including phaser, flanger, pitch and octave effects, fretless and sitar emulation, pickup and acoustic guitar emulation…the list goes on and on.

A very cool new category introduced with the GT-100 are the ACCEL FX. The six different effects in this group—S-BEND, LASER BEAM, RING MOD, TWIST, WARP, and FEEDBACKER—are primarily designed for momentary use, letting you bring in dramatic and expressive sounds on specific phrases with the GT-100’s dedicated ACCEL footswitch. For example, S-BEND lets you employ a pitch shift of up to four octaves for some insane whammy-style effects, while FEEDBACKER lets you bring in controlled amp feedback tones at any time and at any volume. These great ACCEL FX really add a lot of expressive potential to your sonic landscape.

Intuitive User Interface and Unmatched Real-Time Control

As I touched on earlier, the GT-100 features an incredibly intuitive user interface with dual displays, along with eight knobs for controlling the parameters shown in them. What’s awesome about this twin-display approach is that you can always see the parameters for any particular effect or function—you just make a selection in the left display, and its parameters show up in the right display, ready for tweaking with the knobs. This setup eliminates endless scrolling through menus and makes sound creation quick and easy. And when you’re not tweaking sounds, the dual displays provide a lot of real estate for patch numbers/names (in large type that makes them easy to see on stage) and info about what’s going in the current patch.

The EZ TONE feature makes creating patches even easier, particularly if you’ve never used a powerful multi-effects unit before. Just press the EZ TONE button on the panel, select a style of music (blues, metal, jazz, etc.), and then choose from a number of variations in the selected style. That’s it! If you want to adjust the selected sound a little more, a simple EZ TONE grid editor and ambience knob lets you fine-tune the tone to taste.

Another thing that’s unique to BOSS’ GT series is the massive amount of real-time effects control that’s on tap. Using the footswitches and expression pedal onboard the GT-100, external footswitches or an external expression pedal, and/or MIDI, you’re able to control up to 15 different parameters in a single patch . This includes things such as tap tempo, switching COSM amps, tweaking amp gain, boosting for solos, and adjusting any parameter in any COSM amp and effect. And that’s just scratching the surface! You can also switch channels on a guitar amp via the AMP CTL jack, turn the GT-100’s effects loop on/off, control external MIDI devices, and much more.

Looper, Stompbox-Style Access, and More

The GT-100 features a built-in looper with 38 seconds of mono recording time (19 seconds in stereo). You can set up the looper to record with all your GT-100 amp and effects sounds, or record dry and process the sound after the fact. Post-processing is a great way to audition and edit effect sounds without having to play as you tweak. There’s a dedicated footswitch for controlling the looper, so you can have it ready at all times for capturing and overdubbing loops. You can also assign additional looper controls to internal and/or external footswitches for expanded operation.

With the GT-100’s quick-access Manual mode, you can use the eight onboard footswitches for quick stompbox-style on/off control of any effect in a patch. To enter Manual mode, just press the BANK UP and BANK DOWN switches simultaneously. In addition to effects on/off, you can assign other commands to the footswitches in Manual mode, like AMP CTL, tap tempo, looper controls, and more. Your Manual mode settings are stored along with other patch settings, giving you access to a unique custom pedalboard with every patch change!

Other features include a chromatic tuner, as well as a built-in metronome for music practice. There’s also a Global EQ—which gives you the ability to adjust the overall tone of the GT-100— and master noise suppressor and reverb level settings. These useful functions are essential for tailoring the GT-100’s sound to different performing environments without having to tweak sounds in individual patches.

Maximum GT

If you’re serious about tone and need access to a ton of great amps and effects, you really need to test drive the GT-100. It sounds amazing, and the COSM amps are a true joy to play, with a touch and feel that’ll make you forget you’re playing a digital processor. With the GT-100, a whole new universe of awesome tone and digital power is at your command.