CoAxe Pickups: Interview with VOX R&D

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CoAxe pickup on SSC33TB CoAxe Pickup Internals

As you can hear in my recent video review of the Vox SSC33, the Vox CoAxe pickups sound amazing.  They’re dynamic, noiseless in all modes, and most importantly offer up a wide range of incredible sounds.

With the two blades sandwiching the pole pieces, you can see right away that these aren’t your typical humbucker, single-coil or P90…

Curious for more details on these mysterious creations, I got in touch with the man behind the magic- the inventor of the CoAxe pickup: Eric Kirkland, Chief Designer at VOX Guitar Development (G-Rok), in Novato, California.    Read on…

Why the name CoAxe?

Eric: The name “CoAxe”, of course, refers to the orientation of the coils.  Stacked humbuckers (the so-called “stacked single coil” pickups) are also coaxial, but our pickups are co-planar as well.  Maybe “Concentric” would have been a more descriptive name, but it just didn’t sound cool enough.

CoAxe Bobbin AssemblyTell us about those blades, poles and coils!

Eric: The arrangement of the coils is significant, as is the position of the blades between the coils.  The inner sensing coil, with its load of six poles, works like any single coil.  Since the load of the outer noise canceling coil consists of both the six poles and the two blades, less wire is required to produce a noise signal equivalent to the noise in the inner coil.  Less wire means less impedance, so the Clean and Crunch modes can be both noise-free and sparkly.  (Exposed to typical ambient EMI, our pickups have less noise than a covered Gibson PAF type humbucker – and more output.)

 

 


What type of magnets are used?

Eric: Ceramic – very similar to those used in the Three-90.  The higher coercivity of ceramic (compared to Alnico) makes  it possible to develop enough power across the available space between the poles and the blades.

What are those “Crunch”, “Lead” and “Clean” modes, really?

Vox 4PDT Mode Selector SwitchEric: Beyond the bandwidth and signal/noise advantages from the coil arrangement, we get the different voices by selecting either the tap or full winding of both the inner and outer coils.  So two poles of switching are required for each pickup, or a 4PDT master as on the Series 33.  Further, the Series 55 makes a third mode available by adding passive filtering to shape the Crunch sound into the more mid/less treble Lead sound.  This requires another two poles of switching for each pickup, or a pair of 4PDTs.

Do you mean “4P3T” there for three-way switch in the 55?

Eric: Using standard switch nomenclature, they are 4PDT as there are only two “throws” available for each pole.  In the middle position, half the poles go one way and half the other.  To be more specific I should have called them “4PDT On-On-On” to distinguish them from the somewhat more common two position 4PDT, as used on the Series 33.

How does the CoAxe compare with other humbucking pickups?

Vox CoAxe Operation

Eric: It has always annoyed me to see manufacturers focus on DC resistance.  IF every other component were held equal, DC resistance can give you some idea of the output level and tone of a particular kind of pickup.  But since there are so many other variables, it doesn’t really tell you much except the approximate length of wire used – assuming you know the gauge.  A better indicator is inductance.  On the CoAxe, the inductance of the Clean mode is around 3.1 H, which is about what you would see in the single coil pickups from a certain large manufacturer whose name begins with F.  The inductance of the Crunch mode is around 5.3 H, and the Lead mode measures around 6.3H.

Are the bridge and neck pickups identical, or are they wound differently?

Eric: They are just the same, and the appropriate levels are dialed in by height adjustment.  We tend to run the neck pickup relatively far away from the strings to balance it with the bridge pickup and avoid interfering with the string vibration.

How do the CoAxe pickups differ from the Three-90 in the Virage?

Three-90 PickupEric: The Three-90 has three conventional (side-by-side) coils that are combined in various ways to create the different sounds. Two adjacent coils are combined in series for the ‘lead’ voice, the outside coils are combined in series for the ‘crunch’ voice, and two adjacent coils are combined in parallel for the ‘clean’ voice.

The Three-90 gives a great range of tone change across the modes.  For the CoAxe, however, we wanted to increase the output level of the ‘clean’ mode for a more aggressive single coil sound.  Also, we wanted to add some emphasis to the attack on all modes, so we went with a separate polepiece for each string in the sensing coil.

Thanks to Eric for generously sharing his expertise!

Additional Resources and Updates:

June 8, 2017: More information on components from Eric:

The same bridges were used across the board on Indonesian, Korean, Japanese, and US guitars. The earliest Fujigen Virages used a tuner with a shield shaped back plate, and of course the Three-90 pickups. Almost everything else used CoAxe Modern pickups and round back tuners. Only the HDC99 and a few US Custom and Japan Custom guitars used the CoAxe Vintage, and a tiny handful of US Custom guitars used different tuners – Sperzel or Hipshot. G-Rok set up a few earlier guitars with later parts for artists, and some of these are probably floating around out there somewhere.

June 12, 2017: Information from Eric on the difference between Vintage and Modern CoAxe pickups.

The physical differences are that the sensing coil of the Vintage has screw poles instead of solid slugs (for less load), and more turns of the same wire to reach a similar inductance to the Modern (though with a higher DC resistance).  The Vintage has more of midrange emphasis than the Modern, slightly lower output, and still better (well, more anyway) highs than a traditional humbucker.