The Blues Junior IV adds to one of the world's most beloved amplifiers with a modified preamp circuit, silky spring reverb, and updated aesthetics. Three 12AX7 preamp tubes and two EL84 power tubes drive the amplifier's power supply and dynamic sound, while a 12" Celestion A-Type speaker handles sound reproduction. With this combination, the amplifier adapts versatilely from bright clean sounds to ripping solo tones, with the amount of distortion responding musically to the guitar's own volume.

To shape the sound, the amplifier features equalization for bass, midrange, and treble, equipped with a FAT mid-boost, along with a classic Fender spring reverb to create a sense of space.