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Boss GT-8 Dual COSM Floor Guitar Processor


Boss GT-8 Guitar Effects Processor
Boss GT-8 Floor Guitar Effects Processor

The Boss GT-8 is a floor based digital guitar processor with two COSM amp and speaker simulators with digital effects. It’s meant for the intermediate to professional guitarist and can be used with your own amp or for direct recording. Its main feature is the dual COSM systems which were developed by Roland. COSM or Composite Object Sound Modeling is a process where a guitar amp or effect is recorded then analyzed and the results are stored as a model. The GT-8 has two COSM guitar preamp systems which can be look at like two separate amp channels. They can be run simultaneously or switched between. It is used to not only model amps and speakers but effects and mics as well.

Some of its main features are the 46 guitar preamp/speaker groups, 340 total presets with 200 factory and 140 user. A Solo Switch function allows you to play guitar leads which boosts your signal volume as well as distortion. It has 44 effect categories and can have up to 13 FX blocks running simultaneously. As for assigning effects you can arrange them in order and change the order of the effects at anytime. It has a built-in tuner that allows you to turn off using a dedicated button found on the top panel. This allows you to tune your guitar without having to hear it. There is also an External Effects output which allows you to use your other favorite stomp boxes and rackmount effects. With the Amp Control function you also switch between the channels of your present amplifier as well. Being a digital processor the GT8 operates at a sample rate of 44.1kHz and a bit depth of 24-bits and comes with a stereo S/PDIF output for direct recording. It also has a stereo headphone out for practicing in silence.

It has 46 different of guitar preamps to choose from. Select a tone from clean twang to ultra-distorted. When selecting a speaker cabinet the default speaker is used or you select a different speaker cabinet. Add to that an additional overdrive or distortion pedal, chorus, delay … and a reverb. It’s that easy. The processor has both guitar preamp models and overdrive and distortion pedal models all contained within the box. They interact in the same way as they do in the real world. For instance you can select the Fender Pro Reverb as your guitar preamp/speaker and then insert a BD-2 overdrive pedal you’ll get a sound that is fairly close to what it sounds like in the real world. Along with the preamp/speaker emulations there is a digital effects processor. You can chain up to 13 effects and arrange those effects in any order you would like.

The digital effect processor is simple to use with its 44 effect type categories. Included effects are delay, chorus, reverb, compressor, Wah, and EQ. There are also two other effects labeled FX1 and FX2 which are assignable effects. The types of effects found here are the more exotic ones like a more advanced compressor, limiter, touch Wah, guitar simulator, tremolo, flanger, phaser, vibrato, ring modulator, defretter, sitar simulator, feedbacker, humanizer, and slicer. FX2 can be assigned to any of these effects: Harmonist, Pitch shifter, octave, rotary, 2X Chorus, Guitar Synth, and Acoustic Guitar processor. These effects are inserted into your effect chain as FX1 or FX2. Some of the effects are modeled from other famous effects. For instance the compressor found in FX1 can be a model of the Boss CS-3, or MXR DynaComp, or Orange Squeezer. As for some of the more interesting effects the GT-8 has a sitar simulator which gives the guitar a sitar like sound. You can add as much of the sitar sound as you want. It also has a buzz function which adds more buzz which is usually caused by the when the strings contact the bridge. Another interesting effect is the Defretter which makes your guitar sound like a fretless guitar. It slurs between the notes sliding up or down depending on which way you go. The Humanizer effect gives the guitar human vowel like sounds. The Slicer effect adds a strange disjointed effect that it has a rhythmic quality and can be synchronized to a tempo.

The reverbs are fairly good as they compare to studio reverbs. Types included are Ambience (early reflections), Room, Hall1, Hall2, Plate, Spring, and Modulate. It has an adjustable reverb time that ranges from 0.1 to 10 seconds in length. For delays the maximum amount of delay is 1.8 seconds (both delay modules running in series). The delays are highly configurable. It includes a mic preamp section that allows you to select not only the guitar preamp and speakers but also the mic and preamp used to recorded the amp.

There is also a master effects section which allows you insert a noise suppressor, adjust the master volume of the GT-8, set the BPM, and who the Volume Pedal response. The noise suppressor can be inserted in to the guitar’s signal path to reduce the amount of noise and hum from the guitar. It does effect how the guitar sounds especially the attack and decay of the guitar note. Too much noise suppression takes all the punch out of your sound while not enough means – more noise. The threshold can be set to loudness at which the noise suppression is in effect. There are three different points at which the noise detection takes place: input jack, after the volume pedal, and at the input of the noise suppressor. You can place the noise suppressor where ever you would like but preferably before any effect that is audio envelope related like reverbs, and auto Wah type effects. The Master BPM can also be set in the master effects. You can also select it to read the incoming MIDI data and use its tempo or you can set it to a particular tempo which will be used by any effect that is tempo based. You can also select the volume curve of the foot pedal from logarithmic to linear to exponential.

You can select from a number of different guitar preamp types as well as set the gain, bass, mids, highs, presence, level and the bright switch if used. You also have control over the amount of gain for the solo switch which when pressed (Footswitch) the tone changes to one that is more suitable for soloing.

The preamp/speaker combination types are broken up into different sounding groups. The preamp section consists of 10 different basic groups of preamp types and two custom types. Each group has a number of different amp models with the JC Clean group having 4 types based on the Roland JC120. Next is the TW Clean group which is modeled after the Fender Bassman, Twin and Pro Reverb vintage amps. The Crunch group has a natural sounding Crunch distortion, Blues tone, Wild Crunch, and Stack Crunch which is high gain. The Combo group is based on the Vox-AC30 Top Boost and Matchless C30 amp and has a couple clean to distorted tones. The BG Lead group has 5 models from the Mesa Boogie amps. These vary from rhythm and mild drive to lead and more overdriven sounds. The MS Stack group is the Marshall Stack group which is based on the 1959 amp. It has 5 different variations. The R-Fier group consists of 6 different amps based upon the Mesa Boogie Dual Rectifier amp. From clean to modern sounding distortion. The T-Amp group consists of 4 models from the Hughes and Kettner triamp with sounds ranging from clean to edgy lead. The HiGain group has 4 models with one from the Soldano SLO-100 amp and three other preamps with varying amounts of distortion. The Metal group has 3 different models one of which is based on the Peavey EVH 5150 tube amp. It also has two other Metal sounds.

There are 46 different guitar preamp models can be used with the original speaker that was used with the amp or select from 7 other speaker cabinets ranging from a single 8 inch open back to a full stack. Each preamp has a default speaker cabinet that was used when it was originally modeled. You can also select a different speaker cabinet with ease. Ever wondering what a 1959 Marshall sounds like through a single 8 inch speaker? You can also select from a number of different speaker types ranging from a single 8 inch speaker to a full stack consisting of eight 12 inch speakers. The single speaker types 8, 10, and 12 inch are of open backed designed along with a 2x12 inch cabinet. These cabinet simulations are designed to interact with the preamp simulation. There are three custom preamp/speaker presets where you can save any you create.

You can also run two different amp combinations at the same time using two channels A and B. The channels can be use in four different ways: Single, Dual Mono, Dual L/R, and Dynamic modes. These modes allow you to switch between them, layer the sounds, or pan them. In single mode the amp operates like you would normally find in most guitar amps. You switch between the two channels using a footswitch (usually Rhythm and Lead). You can also run the two channels in dual mono mode which is like having both channels playing at the same time. Another way is to run the GT8 is dual L/R mode which sends channel A out the Left side and channel B out the right side at the same time. This sounds great in stereo. The last and one of the more interesting modes is the dynamic mode. This mode uses both channels and switches between them depending on how hard you play the guitar. It senses loudness changes and will instantly route the louder parts to one preamp and the lower level parts out the other. This is usually done with a rhythm preamp sound at the quieter level and a more distorted preamp sound when played more loudly. One thing I noticed is it takes a bit of time to get use to playing this way. It’s also a great way to help you learn how to keep the level at a constant level.

When changing between patches you don’t get abrupt sound changes because the preamp/speaker and effects are cross faded when select a new one. This means the previous effect simply fades away while the new effect becomes available.

Even though this is a floor unit it you still have control over your sound using real knobs by turning the gain, EQ, and other control knobs. You can also change the over drive/distortion, delay, chorus, and reverb settings in real time with the knobs. This allows you change the EQ, presence, level and effects settings without having gone in to any menu. This makes it a lot easier to make changes to presets or for just finding the right sound you're looking for. The interface has a preamp/speaker section which has preamp type, gain, bass, mid, treble, presence and level. The preamp type has 10 different basic types and a custom type for creating your own preamp/speaker models.

The ‘Quick Settings’ function allows you to save not only preamp settings and then recall those settings into another preset, but do the same thing with effect presets. This is great for creating new presets based on preamp and effect types you are interested in.

You can use the GT8 with your external effect stomp boxes and rackmounts using the built in external effects loop. With the ‘Amp Control’ feature you can switch between the channels of your guitar amp. There is a ¼ inch phono jack on the back panel which is plugged into the channel switching jack usually found on the back of your guitar amp. It has a polarity switch so it can be used with most amps. It allows you to program which channel of your guitar is used for a given preamp.


  • Dual COSM amp modeling which allows channel switching and stereo operation
  • 46 preamp/speaker models including Fender Bassman and Marshall 1959
  • 7 Different Speaker Cabinets
  • 30 Overdrive and Distortion pedal models
  • 44 Effect Categories including some exotic effects like Sitar and Defretter
  • Up to 13 different effects playing simultaneously
  • 340 Total Presets with 200 Factory and 140 User
  • Solo Switch for instance boost in Signal level
  • External Effects Loop for connecting to your own pedals and rack effects
  • Programmable Expression/Volume pedal
  • Stereo analog outs
  • 24-bit S/PDIF coaxial digital out
  • Amp Control Jack
  • MIDI I/O
  • Headphone Output