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The Boss RT-20 Rotary Sound Processor is a twin stomp-box pedal which uses the breakthrough COSM (Composite Object Sound Modelling) technology by Boss. It's function is to create authentic vintage rotary speaker sounds and add additional overdrive into the mix. The RT-20 is based on classic Rotary speakers from the '50s and '60s and each sound can be adjusted easily using the 'Rise Time', 'Horn' and 'Bass Speed' controls.

The RT-20 has 4 main sound types and an adjustable mix between treble and bass rotor. An in-built digital display provides a visual reference of the virtual rotors. The RT-20 is just as effective with either guitar or keyboards/electric pianos.

GAK's Boss RT-20 FAQ's

Q1: Can I control the rotary speed using an external pedal?
A: Yes, you can adjust the speed of the rotary by connecting a ROland EV-5 expression pedal to the EXP input on the rear of the unit.

Q2: Does the RT-20 have to be connected in stereo?
A: No, the RT-20 can be used in either stereo or mono. Stero outputs to 2 L/R speakers will give a much more realisic stereo pan.

Q3: Can I use other instruments with the SL-20?
A: Yes, you can use any instrument with a 1/4" jack input. The RT-20 does work best with a guitar or keyboard/electric piano.

Q4: How long is the battery life?
A:The RT-20 uses a 6 x AA typedry cell batteries. The SL-20 can also be powered by an optional AC adapter such as the Boss PSA.

Call GAK now for product info, advice and the Best Prices - 01273 665400

  • Authentic rotary speaker sounds by COSM technology
  • Slow/Fast transition time is adjustable from gradual to rapid change; optional Expression pedal can control speed in real time
  • Onboard Overdrive effects
  • Adjustable mix balance between Treble Rotor and Bass Rotor
  • 4 types of sounds, from standard rotary speaker effects to rock-oriented tones, UNI-V, and more
  • Guitar/Keyboard switch
  • Dazzling virtual-rotor display



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  • Lee Frost


    Its spacey man.

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