Originally introduced with the AC15 back in 1958, Vox's AC4 is one of the original British guitar amplifiers - in fact, the AC part of the name refers to Alternating Current mains power, which not all areas of the UK had back then.
Originally called the AC2, Vox renamed it the AC6 and then the AC4 in around 1962, with no significant changes to the circuit, which featured a built-in tremolo and three controls for volume, tone and speed.https://youtu.be/belXOIYf7sc
The modern version has a completely new circuit, and Vox also upgraded the speaker to a proper 10-inch Celestion. Now, it's gone a step further by releasing a 12-inch version, appropriately called the AC4C1-12.
While the AC4 looks similar to a mid-1960s product, the internals are significantly different from the originals, which used an EF86 preamplifier and an EZ80 rectifier alongside a single EL84 power valve. The EL84 remains and is now powered by a solid state rectifier and driven with the more common but less troublesome 12AX7/ECC83 in the preamp.
The circuitry is printed-circuit based, using a non-plated board in a simple L-shaped steel chassis. Alongside the single-input jack socket, there are chicken head knobs for preamp gain, bass, treble, and a master volume.
Because the AC4 is a pure single-ended Class A design, the EL84 runs hot - very hot in fact - with a lot of heat conducted to the control panel. Overall, the AC4 is a good-looking and well-made little amp.
Used at lower gain levels, the AC4's clean sounds are typical of what you might expect to hear from an early Vox - a boxy midrange and restrained bass coupled with a zingy treble that needs to be carefully tamed.
Set that treble knob right, though, and you get the chiming chord effect that makes the AC4's bigger brother one of the great rhythm guitar amps. Turn up the gain some more, and the AC4's blues/rock alter ego appears, with a sweet singing sustain that's great for invoking the original British Invasion vibe.
The AC4 is ideal for home users, and great for lower-volume environments, and the bigger speaker lends more authority and punch for live use.
This amp was bought new in Sydney in xxxx and has done little work since. Used mainly in a home environment and looked after well, the amp shows no sign of use – just like it came out of the box yesterday.
This is a great sounding little Vox with all the chime, snarl and punch you expect from an amp with that revered UK brand name.
Video demo here - https://youtu.be/belXOIYf7sc