Vox "CoAxe" Pickups

[newey]

The new Vox guitars feature their "CoAxe" pickup coil technology which I thought was interesting- an inner coil embedded in an outer coil. Both are tapped at various points in the windings to simulate SC, P-90 and HB sounds, all hum-cancelling.



Previously, these were available only in the Vox Virage guitars, which are woefully overpriced, but these pups are now available in the much more reasonable SDC33 model, $700 USD at MF:

[Yew]

I read about how you could theoretically cut part of a coil, taking it from a p90 , to a single coil sound... didnt know it was actually done though

[sumgai]

".... outside the magnetic flux."

Say what?

Do any of the currently living Electrical Engineers know about this? How about any currently living physists, medical researchers, or for that matter, anyone of scientific bent?


Doncha just hate it when Marketing Departments shoot a new idea right in the patootie? I might've been interested, but now.....

We all know how ChriK would have designated this little fiasco, right? (Hint: starts with an "F".....)



sumgai

[Yew]

looking at soem high res pictures... is that a P90 and a blade humbucker in the same pup?

[asmith]

Unique technology? It's the same 'technology' as Faraday and Henry.

"Organic" pickups?! Get me the President!

That said, an interesting idea. I refuse to accept that in 'humbucker' mode it's a true humbucker - as far as I can tell from the video the inner coil is always silent. To my dictionary a humbucker is two coils in series - regardless of whether the design bucks hum.

[JohnH]

A couple of these Vox guitars are featured in Australian Guitarist this month, It says the hum cancelling coil has low impedance and a low number of winds. Im thinking it gets it anti-hum to a sufficient level because it has a larger area than the main coil. So Im also thinking, maybe theres a GN version possible, where we take a standard single coil and put it at th centre of a larger coil under the pg, wired in series with it.

[4real]

It makes sense and in line with general 'noise cancelling' technology thee days. The metal blades act as a conduent for the magnetic flux to pass from the north to south poles of teh magnet...the noise cancelling coil is somewhat outside of this pathway.

This is the same idea as Kinmans and fenders etc....using side magnets to create a more figure 8 pattern.

Additionally, by having the coils outside, the windings are significantly longer to go all the way around, so you need a lot less windings to get a similar value...similarly the core changes the inductance and the value, different wire gauges affect things as well.

But it is not litterally a P-90, single coil or HB. It is "humbucking" in that there is one sensing coil and another noise cancelling coil....just like a stacked coil has the sensing coil on top and another noise sensing coil well away from the strings...or that shur cavity plate idea and other dummy coils...the size, windings, wire and shape can be radically different and still pickup 'noise' and cancel it out if matched to the sensing coil arrangement.

Kinman even goes so far as to produce a 'faraday cage' to magnetically isolate one coil from the other and control the magnetic effects on the sensing coil and isolate it from the magnetic flux sensing the strings.

I played with similar ideas with the sustainer things...many of my drivvers were 'co-axial' in tha tthey shared the same axis...doh!

Basically. people have caught on to the idea of things like the SD P-rail to get different sounds, the fetish of the P-90 in recent times and the idea of wiring to create different pickup options...something nutz have been doing for some time!

Throw about a few mojo terms like 'co-axial' and 'organic' and 'P-90' and you are sure to sell a few!

...

It's an interesting if 'old' idea though that has not been seen for a while...the idea of tapping off the windings. You can make a bit of difference in this way...you can alter things a lot by switching in an out coils, running things in parallel and series and phase...etc. What you can't really emulate is the difference betwen a side by side Hb (which this is not, those blades are not opposite poles) and a true single coil or stacked design.

It may very well have three distinct and great sounds (interestingly he does not demonstrate them at all, resorting to mojo terms) but as the magnetic 'shape' can not be altered, there is only the windings to play with....changing resonance and such.

Interesting trend though where pickup makers are working old tricks to get a range or sounds out of a single device...like those SD switch rings and other trends these days. It is a good marketing tool, even if your pups are not the greatest, that you might be convinced that you are getting 3 for 1 in the deal may well be enough.

The reality is though, that they may well sound great in all modes if not exactly what they claim to be emulating...might even make a nice new variation with some design tweaking like this...they are not able to switch between different magnetic strengths, formats or shapes of sensing fields.

A P-90 has a very distinctive magnetic arrangement for instance and is very wide, not just hte coil, but the field itself. An HB has opposing equal strength fields and need to be set reasonably close to the strings as the opposite fields are attracted to each other and so have very little 'throw'. A single coil needs space to 'breath' and if set too close, the magnetic field will suppress the strings vibrations at nodal points causing harmonic problems (stratitis) or even pulling the strings slightly out of tune.


So, everything is a slight compromise, but they may still sound great, just not like the 'real thing'...but it's a sales show is't it...the idea is to sell you the pups...so they can and will say anything...even raise a little controversy and further mojo...lol

Not every HB is going to split well, overwound pups seem to do better on one coil but can sound muddy on full blast. A volume control with a treble bleed can 'fix' that to some extent, just turn the guitar down a touch on full HB. My spin select thing does similar things, merging the degree of split and which coi is the dominant one...all one would need to do in marketing is to attach suitable terms like p-90 to them, and i'd be on a winner...LOL

It is good to see that noisecancelling is seen to be advantageous though...the environment around us is getting ever more noisy and with things like digital recording and modeling, noise is not anything like as acceptable as it might have been in the 1950's...

[4real]

I watched a couple of other vids to try and get a handle on the way these thigns sound....



not sure why i have problems embeding vids...anyways...



It looks like a nice enough guitar, sounds ok...but not sure that it is that 'revolutionary' or great a sound that just about any nice guitar couldn't make...as always, hard to hear through the audio quality of the recording...the hype...and the amp, wall of effects and distortions being used which seems to be mking most of the sound quality. Clean, it was kind of bland IMHO and perhaps they compromised a little too much.

Similar with this GW review...nice guitar, good looking bridge...teh hollow body adds a bit to the sound i suspect...but really...there is not that much variation in tone from all those pup settings that nutz here wouldn't get mre of with a bit of trick wiring and some supurb HB's or similar. Looks like DM's answer to the P-rail...but at least with those they can fit into a normal HB ring...

Yes...there is a slight bit more 'hair' on the P-90 thing clean...but not that much change between all the settings, just a bit more power hitting the amps input...otherwise the pups sound dissappointingly similar in all settings. You could get a similar effect by learning to use the volume control!

Shame really that it isn't more effective for teh amount of work that must hve gone into them, I mean, tapping the coil and noisecancelling is a lot of wiring.

Oh well...at least they made a nice looking guitar with some features that gibson could take note of and improve their fortunes...

[JohnH]

I can also see that there is some sense in this design, and did not baulk at the marketing blurb. I think I can see how the extra blades can direct the magnetism, and keep the passive coil 'outside the magnetic flux' , although I haven't the proper terminology to explain.

But, tHe thing is, the lines of magnetic flux go, say, up through the magnet cores (and hence up through the main coil), then curl around the outside of the pickup to return down again. The main coil has all the flux in one direction, and variations in the flux intensity caused by string vibrations will cause a signal induction. However, a very large coil around the pickup, on the same axis will be outside the field, and there will be no change in flux in the coil wires, so no signal induced.

The extra blades of the CoAxe pickup grab those 'down' lines of flux and keeps them contained, so that the passive coil, which is outside of them, experiences little flux, even though it is only a reasonable distance further out.

John

[newey]

Coincidentally, I was in my local guitar store tonight for my lesson, and they have a few of these on the wall. I didn't have time to have the guy pull one down off the wall for me to play, but I will say that they look very nice- gold top with a mahoghany body, nicely bound.

They also had the single-cutaway model and the hollow-body one, each at $999. The hollow body looked particularly nice, with the distinctive "pointy horns".

[4real]

pretty much...it makes some sense and in line with the stacked designs with central mags and such...but in the end...it is just a big single coil pickup with a noise cancelling coil...could sound great...but not going to be 'just like' a p-90, Hb or SC and to my ears, it is a compromise of all three without offering that much new.

I wonder why they haven't pursued the 'dummy coil' idea for SC's...then people might buy that product in droves to quieten strats or other DM pups and really get a SC sound? Maybe just not 'sexy' enough...

The guitar does look very cool...but with the vox brand...hmmm...not sure tehy will be around too long...good price by the sounds of it...

[sumgai]

(EDIT: Added a qualifier to the first sentence, otherwise it implied something that might not be obvious.)

Let me say simply that a coil, any coil, will always have magnetic flux, provided that there is a current flowing through it. Want me to repeat that? Sure, glad to oblige: Any coil, be it air-core or otherwise, will have a certain amount of magnetic flux. It's the nature of the beast. Period. End of discussion.

An iron core, whether it's already magnetized or not, will tend to focus the flux into a shape other than toroidal (in a cross-sectional view). A coil with a magnetized iron core will tend to be very sensitive, compared to the same coil with only an air-core. But that's because any metal within the magnetic field tends to increase the coil's inductance factor..... which is a good thing, for our purposes.


Pete, this system is nothing more than a dummy coil. The alleged placement of being "outside of the magnetic flux" is really just MarketingSpeak, which is to say, they're taking liberties with both the English language and with commonly accepted electrical terms.

If the previous analysis is correct (and I'm not saying it is, sorry 'bout that), then the two bars that isolate the dummy coil from the signal sensing coil are, somewhat, keeping the dummy coil "outside the magnetic flux".... The rest of the story being, 'outside of the magnetic flux of the signal sensing coil'. Which of course is perfectly fine, there being no law that requires two coils to share the same flux/field in physical space. (See the Suhr system.)

But let's not forget Rule #2 - In case the dummy coil is outside of the magnetic flux of the signal sensing coil - it still has it's own magnetic flux to contend with. See Paragraph 1, above.

All in all, this is nothing more than a localized dummy coil. Not very costly to make, not very hard to install, has boundless opportunities for MarketingSpeak (endless allusions to Mojo^™), and certainly has room to improve and grow.



As to the tonal capabilities of this thing, I agree with most of you, tapping a coil does have its advantages, and gives rise to a lot of potential Nutziness. Let's see how long it'll take for the pickups themselves to become available as replacement parts, and thence wend their way into non-Vox kit.


HTH




sumgai

[newey]

Yeah, I thought the coil tapping was more interesting than the dummy coil thing, there are lots of designs that cancel hum in one way or another.

As I understood it, both coils are tapped in 2 different places to give the 3 choices.

[sumgai]

My further thoughts on coil-tapping.....

When a coil has multiple-thousands of winds, then it's not critical just where you place a tap. If you're wanting to approximate about 1/3 of the way through, that doesn't mean that you count exactly x/3 turns, it means that you're aiming for it, and if you miss it by 10, 20, or even 50 turns, so what. But keep in mind that this kind of coil is using very fine wire, and has a pretty high impedance....

Contrast that to the alleged hum-reducing coil, which is not intended to sense any string vibrations, or at least, not intended to produce any tonality from any such sensing. This coil is touted to use larger diameter wire, and to have many fewer turns, which of course results in much lower impedance. I'm sure it won't take a rocket scientist to see that we must now be much more accurate in determining just where to place any taps. If we don't take that extra care, then we may well end up with two coils that sense different amounts of extraneous noise (hum, etc.) and they would no longer match close enough to "buck that hum".

It's both a science and an art, and I can just imagine the high-quality robotic machinery needed to try and keep the results uniform from one item to the next. Trying to do this by hand would be a nightmare, and IMHO, a very unprofitable proposition. It will be interesting to see if "quality control issues" crop up, resulting in a prospective buyer going out and testing three guitars of the same make and model, sitting side by side, and yet he/she feels that one of them "just doesn't have it, the sound isn't quite right".


The usual disclaimers apply, of course.




sumgai

[thetragichero]

this is why i like you guys
cut the mojo bs, get down to the science!

[Yew]

Just had a thought here.

A P90 is a single coil, with more winds right (and a diffferent shaped bobbin) but otherwise the magnets and stuff are pretty similar.

So if you had a Humbucker, With a normal coil tap. and a coil tap at a point through the second coil (to give it a similar output to a P90) could you get all of these sounds from a single pup?

aboutn the hum, well some nice foil would do that nicely

[4real]

No...P-90 magnets are quite different..two like poles against the centre poles...this make a very wide field. The extra metal rails to the side of the centre in this design provides a conduit for the magnetic field to return back to the opposite poles beneath.

In an HB, you have two opposite poles close and facing the strings, so they will be attracted to each other and through the strings, low string pull as the two poles are counteracting the forces on them. The magnetic field is largely going from pole to pole and not so 'wide' or have the 'throw' (having to go up and all around without the magnetic lines crossing)

A single coil has a lot more 'throw' as the field lines have to go up and all the way around to return to the opposite poles underneath the pup.

So, all the magnet structures are quite different and are not changed by simply changing wiring, tapping or splitting coils.

So...you can not get an actual P-90 (or a single coil from a split HB) and there is only so much you can achieve from foil (as this does not do much for magnetic interference at all)...

Changing the size and number of windings won't necessarily make a good sounding pup in both modes either, you are changing the inductance and resonance of the coils...

But that doesn't mean you couldn't find a nice balance that makes multiple useful sounds unique to the design.

"P-90" seems to have become a bit of a mojo term. 'A bigger warmer single coil with a bit of hair and more bass than a fender' might be a better description. You could perhaps say that a half/split Hb might make this sound (possible with the spin-select type control) by having one coil and fading in a little of the other for more power,bass and width of sensing. Of course, the magnetic 'shape' is quite different, but it gives something of this flavour...as you suggest. You also get quite a bit of noise cancelling from the additional rwrp coil being wound in, more so than a real P-90.

There is a neat program called FEMM that allows you to draw magnets and different materials so that you can see the magnetic lines and strengths along them. Steven Kirsting used it to model the magnetic lines of common pups and his own variations. He has a pup that is in a SC fender format with P-90 like magnets under and more windings for instance...these magnets like a P-90 force the magnetic sensing field quite wide...but there is still the compromise that the bobbin is tall and not wide and flat like a P-90.

It could be worth exploring a switch for a split that switched in a resistor (potentially flavoured with a cap) for a sound between a split and full HB rather than having to find the sweet spot on a spin-a-split or spin-select control.

One of the 'problems' with this co-axe things is that it is a unique size and not able to be retrofitted into say HB guitars easily. It has to be that way, like a P-90, in order to let that outer coil go all the way around the entire pup