The Double Four is a single-channel bass amp with a simple three-band EQ (bass, middle and treble), a passive/active/mute switch with clip LED on the input, a master volume, a headphone jack for practising, and a line out for recording. There’s also an aux in with its own level control. It’s very similar to the Session 77 combo amplifier, but is purposely designed for use around the house rather than onstage or in the studio. The speakers are a pair of four-inch PJB NeoPower Type C drivers, and the total power output is 70 watts.
But just because it’s a practice amp doesn’t mean you have to cut corners with your sound. The cabinet may be around the size of a lunchbox but it’s built to the same standards of all PJB cabinets, which means it employs heavy bracing and acoustic damping to ensure the clearest, most faithful reproduction possible. It also means freedom from a problem that plagues many practice amps: farty low notes. That solid construction and heavy damping means your low B will sound as punchy and clear as any other notes.
As with the Session 77, the Double Four will faithfully reproduce the input signal, whether it’s an active or passive bass plugged directly in, or a processed signal making its way into the amp through a preamp or effects unit. It also means the auxiliary input sounds nice and faithful too. Heck, if you wanted to you could use this amp to play music in between sets, should you be playing a small enough room that you can get away with an amp of this size. Because yes, this is marketed as a practice amp, but it pushes out enough volume for at least small gigs, and the line out means you can also plug it into a PA system to effectively use the amp as your onstage monitor while the PA system sees it as a direct box.
This isn’t the most full-featured practice amp ever: there’s no distortion, no compression or limiting, no switchable graphic EQ or any of that extra fun stuff. But it’s totally no-nonsense and will give you back exactly whatever sound you put into it, and in a market sector full of amps that unflatteringly colour the sound, that’s a huge deal.