Complex sentence: In 1991, Marshall began making a guitar effect that was supposed to emulate the sound of the original combo; in 1999, a second version, the Bluesbreaker II, was released.
Split into simpler sentences: In 1991, Marshall began making a guitar effect that was intended to emulate the sound of the original combo. In 1999, a second version of the amplifier, the Bluesbreaker II, was released.