Size and Weight

• The Casio PX-120 measures 52 inches wide, 11 inches deep and 5.25 inches tall at its tallest point. It weighs 25.1 pounds before optional upgrades and accessories. The Fantom-G8 is larger than the PX-120, measuring 55 inches wide, 19.8 inches deep and 7.25 inches tall at its tallest point. It’s also almost three times heavier than the PX-120, weighing in at approximately 74 pounds. The Prelude is the smallest of the three keyboards, measuring 41 inches wide, 12.5 inches deep and 4.75 inches tall at its tallest point. It’s also the lightest of the three devices, weighing just 17 pounds.
  
  

Features

• The PX-120 and Fantom-G8 both have 88 keys, while the Prelude has 61 keys. None of the keyboards has weighted keys, although all three are marketed as being touch-responsive, a feature that allows the keyboards to output varying volume levels depending on how hard you press the keys. All three keyboards have 128-voice maximum polyphony.
  
  Of the three keyboards, the Fantom-G8 is the most advanced in terms of features. These features include a built-in sampler, a sequencer, an arpeggiator, 128-chord memory, 16 pads, a combination pitch bend and modulation lever, eight control knobs and four sliders. The PX-120 is considerably more streamlined, offering an onboard two-track recorder, auto accompaniment tool and built-in effects. The Prelude comes equipped with a built-in sound generator and a backing-track tool.
  
  

Connectivity

• The Fantom-G8 offers the most connectivity options of the three keyboards. Its inputs and outputs include one quarter-inch input, one XLR input, one quarter-inch headphone jack, four quarter-inch TRS outputs, one quarter-inch foot pedal jack, a pair of MIDI ports, one USB port and one combination coaxial input and output. Casio outfits the PX-120 with two stereo mini jacks, a pair of MIDI ports and a quarter-inch foot pedal jack. The Prelude’s inputs and outputs include two headphones jacks, a pair of MIDI ports, one USB port and a quarter-inch foot pedal jack.
  
  

Additional Differences

• The Fantom-G8 has an 8.5-inch backlit LCD screen with a display resolution of 800 by 480 screen dots. The Prelude has considerably smaller LCD with a display resolution of 240 by 64 screen dots. The PX-120 doesn’t have an LCD screen. All three keyboards are powered by AC adapters. The PX-120 consumes approximately 18 watts of power, the Fantom-G8 consumes approximately 30 watts of power and the Prelude consumes 11 watts of power.