Yamaha RBX4 A2M bass review

This four-string wonder aims to reinvent the wheel, but still offer great tone. Has it bitten off more than it can chew?

  • £599
The ultra-modern appearance hints at the unconventional construction of the RBX4

MusicRadar Verdict

An admirable attempt at providing a more sustainable way of making electric instruments without destroying the tone. Any steps in this direction must be applauded, and it sounds pretty darn good to boot.


  • +

    Fresh and ultra-modern construction and design. Impressive passive sounds. Light weight. Superbly balanced.


  • -

    No lights for tone control.

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Just as with guitars, the majority of today's bass models owe allegiance to one or more of the most popular and influential models from the past. But, occasionally, something refreshingly new appears such as this Yamaha RBX4 A2M.

The guitar version came first but in its bass form it's no less impressive in terms of its design and highly contemporary looks. It offers a whole new way of doing things in a more environmentally friendly and sustainable way.


Here the traditional idea of using dense body material is replaced by AIR or, to give it the full term, Alternative Internal Resonance.

This is a construction method that uses a layer of resonant softwood embedded between harder tonewoods with a series of aluminium sound tubes passing through the core from the bridge to allow the string vibrations to achieve clear passage through the body mass.

The claimed result is a purer tone and accentuated natural sustain, along with a definite saving in terms of weight. Although wood is employed in the construction there is no visual evidence whatsoever.

With a pure white top, white pickups and a grey back and neck this bass projects a very stylistic and modern presentation.

A curved top and back to the body with an additional silver beading line on the top edge, plus an unusual split-level headstock, all helps to accentuate this sleek and relatively simplistic look.

What's more when you plug in your lead the two volume controls are illuminated (green for neck and blue for bridge position), and with that all white background they really stand out.

With a white overlay to help match the headstock with the body, the tuners appear almost buried within the overall headstock mass. Also, thanks to the through-body stringing design, this becomes one ultra minimalist design. Yet another Jazz bass it ain't!

As something of a contrast, the bridge is a quite chunky affair with an unusual wrap-over saddle design. But when viewed from the front it takes on the appearance of a solid satin chrome tailpiece block that echoes the finish of the tuners perfectly.

As with the A2 guitar models the hardware and pickups are custom designed by Yamaha Artist Services Hollywood (YASH), which makes use of the professional input from many of its bass endorsees.

And if it meets the requirements of Nathan East, Billy Sheehan and Michael Anthony, the chances are you're going to like it too.

The balance of the RBX4 A2M is simply superb and with the added benefit of a shorter scale the lightness in weight is immediately noticeable. Yet the bass still manages to retain the general feel associated with this well-established and popular Yamaha range.

So, expect comfortable neck proportions with smoothly rolled fingerboard edges and fret ends with plenty of access to those upper frets. String spacing is good and the two pickups provide excellent thumb rests when you play with your fingers.


Although we've made a lot about the reduced weight of this striking instrument there's no lack of performance or output when it comes to playing it. In fact, even before plugging it in you notice a pleasing natural tone.

Any concerns of a lack of performance due to it having a shorter scale length these are also soon quashed as this speaks with a very confident voice indeed.

It also has a distinct and individual purity in tone that makes you wonder if the battery is there to supply power to the visual display or give this an active boost.

Plugged in with the LEDs shining behind the volume controls you see the intensity of glow increase as you lift the control level, so it's easy to see how you've set your sound as well as hearing it.

When talking of twin-pickup basses the iconic Fender Jazz bass naturally springs to mind. Indeed, tonally, the RBX A2M is all about the same fine pickup blending and produces some sweet and sumptuous sounds.

But this bass possesses an overall more modern tonal delivery that seems more subtle, smoother in the low-end yet with a confident edge that ensure cleanly defined notes over the entire fretboard.

Some of this clarity will be a direct result of the slightly shorter scale length, but the main contrast to similar instruments has to come from the pickups. These single-coils with ceramic bar magnets are something of a revelation as they provide a super sweet range of blended sounds.

In fact, it seems impossible to find a volume combination that doesn't provide great results but fortunately there is also a darker element to hand. If you care to dig in a little with a pick the uglier side kicks in showing some serious punch and projection that we like a lot.

Individual volume controls still offer the best way to blend a matched pair of pickups in our opinion and here the sweet spots positively abound.

Most of the tonal variation is achieved this way as, being a passive bass, the tone control merely rolls off the highs - it doesn't boost anything. But whether stroking it or digging in, this bass possesses a very pleasing voice indeed.

If you're looking for something a little different that will stand out at any gig then this Yamaha has a lot going for it.The stylish and clean, modernistic approach offers something entirely new and with both short- and long-scale models, and a five-string as well, this range offers something for everyone.

Any thoughts that this very different constructional approach using sustainable materials results in a less dynamic delivery than is achieved by using traditional methods should be abandoned right now.

In direct comparison to similarly equipped basses, this holds its ground very well indeed. Reservations are purely cosmetic; illuminating the controls is a pleasing idea, but not giving the tone control similar treatment seems a curious decision.

But as far as performance goes - sound, feel and looks - this A2 bass is without doubt a very viable instrument that should win many fans.