The Blues Junior IV is a one-channel tube combo rated at 15 watts. It uses three 12AX7 preamp tubes and two EL84 power tubes, driving a single 12-inch Celestion A-Type speaker with a total impedance of 8 ohms. This revision has a reworked preamp circuit for a fuller sound and a spring reverb tuned to sound smoother.

Controls are Volume, Treble, Bass, Middle, Master and Reverb, plus a Fat switch that boosts the midrange. A one-button footswitch comes with the amp and switches the Fat function remotely, for example to thicken the tone during solos.

The amp has one 1/4" input. The cabinet is 3/4" particle board covered in textured vinyl, with a black front panel, lightly aged silver grille cloth, ivory chicken-head knobs, a red jewel light and a molded plastic strap handle with a steel reinforcement band. It weighs 14.3 kg. Versions are listed for 230V EUR and 230V UK mains.