What is Guitar Pickup Calibration & Do We Really Need It?

Bob Leggitt | Thursday, 7 May 2020 |



Problem... On an electric guitar with multiple pickups, the vibration of the strings is greater above the neck pickup than it is above the bridge pickup. And greater vibration means higher volume. So with exactly the same pickup design covering both neck and bridge roles (and both pickups set the same distance from the strings), the output from the neck pickup will be louder than that of the bridge. Flicking between neck and bridge pickups will not only cause a drop in output volume, but also a drop in tonal substance due to the more restricted string travel nearer the bridge saddles.

When electric guitars were in their infancy, they typically only had a single pickup, so there was no issue. But once two or more pickups became commonplace, the above problem had to be addressed. Early on in the timeline, the standard means of compensation was to adjust the heights of the pickups so that the neck unit was farther from the strings than the bridge unit. But this was not an ideal system, as there are other criteria involved in optimising pickup height, and sometimes the amount of compensation available from height adjustment simply wasn't enough to even up the output.

A much more effective means of positional compensation is pickup calibration...

WHAT EXACTLY IS PICKUP CALIBRATION?


Fundamentally, pickup calibration is compensating for the aforementioned problem by engineering each pickup differently, depending on its intended position on the guitar. So with a two-pickup guitar, you have a bridge pickup optimised for the bridge position, and a neck pickup optimised for the neck position. The two units will have a different number of coil wraps, perhaps a physically different coil shape, and they may also have different magnet strengths, types or dimensions.

But there are two different understandings of what calibration means. One understanding is that the pickups on a multi-pickup guitar are engineered to produce both even volume and an even frequency response. They’ll still sound different from each other, because of where they’re placed. But in this version of calibration the personality of the pickups will be constant. In particular, you’ll notice exactly the same amount of top end sparkle, even though the placements of the pickups vary their midrange and bass end.


Way, way ahead of its time, the Fender Telecaster/Broadcaster introduced calibrated pickup designs from the very birth of the commercial electric solid guitar.

In the other understanding of calibration, the pickups are still designed to even out the volume differences beneath the different points along the string length. But instead of being engineered for a flat personality from one position to the next, the personalities are tweaked to suit the position. Most typically, the bridge pickup will be spec’d to produce more midrange, so it sounds fatter, while the neck, or neck and middle, are engineered to sound more hollow. You’re bringing in tonal compensation as well as just volume compensation. And you’ll probably notice a little less high end treble bite on the bridge pickup.

CALIBRATION HISTORY


Fascinatingly, one Clarence Leo Fender actually adopted pickup calibration on Day 1 of the commercial solid guitar. His Broadcaster, prototyped in 1949, produced from 1950 and subsequently renamed the Telecaster, had completely different pickup designs for the neck and bridge positions. Play a Telecaster with the original pickup spec, and the output balance between the two units is near perfect. You don’t get a noticeable drop in volume when switching from the neck to the bridge.

But other companies, some of whom had already been producing non-solid electric guitars, did not follow Fender’s individual calibration idea.

That was a problem for Fender, because if Fender were going to port calibration over to subsequent models, they were going to be at a financial disadvantage. Tooling up for two separate pickup designs, or three on the Strat, was going to cost money that the rivals were not having to spend. And that would affect the price of the guitars at the point of sale. Producing a guitar that cost more to make, would either mean a higher retail price (so a less competitive product), or reduced profit margins.


Despite Fender's new precedent for specific bridge and neck pickup dedication, Gibson continued to see no need for calibrated pickup designs, and introduced the Les Paul with unbalanced neck and bridge sets drawn from universal stock.

The lack of pickup calibration didn't affect Gibson guitars as much as it did Fender, because Gibsons tended to have separate tone and volume circuits per pickup. This meant the guitarist could notch back the volume a little on the neck pickup, and get a totally even balance when switching to the bridge. Again, this wasn't a perfect solution, because notching back the volume introduced resistance, which rolled off some top end. Not a major thing in the days when sonic reproduction was lo-fi, but it would become a bigger problem as the fidelity of recording and listening systems improved.

And Fender also had to admit that on their infant Telecaster, the inaccurate, hand-guided pickup winding of the period meant that even pickups with the same spec would vary. So whilst Tele pickups were designed with ideal calibration, an over-wound neck unit was not going to balance correctly with an under-wound bridge. Manufacturing processes just weren't ready for pickup calibration in the 1950s, and no one really cared that much about it. So when the Fender Stratocaster arrived, it dispensed with the position-specific pickup designs of the Telecaster, and adopted three pickups of universal spec.

But let's be clear. The Strat did not have Gibson's separate volume circuits per pickup, and that, coupled with the guitar's low-output pickup design, would leave its bridge pickup exposed to criticism in the following decade. The Strat's single coils were on the lower limit of gain-tolerance, and the drop in string volume when switching from neck to bridge would frequently exceed the player's tolerance threshold. The Strat's perceived "weak back pickup" encapsulated the problem with uncalibrated sets, and eventually sparked the revolution that normalised calibration.

'NERDS' TO THE RESCUE


It wasn’t until the 1960s, when the first real wave of electric guitar ‘nerds’ began to differentiate between older and newer instruments, that the notion of two supposedly identical pickups having significantly different spec, gathered pace.

The emerging consensus by the late 1960s was that the pickups on many older guitars sounded better than those on new ones. This was explained by ‘improvements’ in the manufacturing process, which had put a stop to what was technically over-winding in many pickups of the late 1950s and early 1960s. But those rogue extra coil wraps frequently found on older pickups gave a fatter tone, with higher output volume. That suited the new, heavily overdriven sounds that were trending post 1966. So old-style slack production had actually created something more desirable than the better controlled production of the then present day.


Due to its universal volume control and relatively low output, the Fender Stratocaster was the one legendary guitar that showcased the problem of uncalibrated pickups more than any other.

And as flighty guitarists began to pursue older guitars, they found a flipside to the incidence of over-wound pickups: under-wound pickups. Under-wound pickups were also common on older guitars, and they were weaker in volume and thinner in sound. More so even than those on the new guitars of the late 'sixties.

The 'nerds' realised that if they put an over-wound vintage pickup in the bridge position, and a correctly-wound or slightly under-wound unit in the neck, they could even out the volume discrepancy, and get a fatter lead sound which really sang through an overdriven amp.

There was no aftermarket for pickups in the formative phase of guitar ‘nerding’, which meant there was only one way to get a hot Strat or Les Paul pickup. Find, and buy, a hot vintage Strat or a hot vintage Les Paul.

As the quest for ‘that sound’ intensified, some of the more affluent guitarists began buying multiple old guitars, and creating one blindingly good one with the best parts. That’s exactly how Eric Clapton assembled ‘Blackie’, his synonymous pre-CBS Stratocaster. Knowledgeable guitarists who could only afford one old guitar would typically at least make sure its hottest pickup went into the bridge position and its coolest went into the neck.

The happening musicans of the day had begun compiling their own ‘calibrated’ or ‘matched’ pickup sets. And at the top of the tree they were way ahead of the guitar manufacturers in what they understood about tone and volume relationships.

INDUSTRY REACTION


By the end of the 1960s, much of the major electric guitar manufacture had gone corporate, and the heads of mass production didn’t really care that a beefy ’63 Strat could put 15% more poke into a Marshall stack than a comparatively brittle late '60s Strat. To the corporate-run companies, it was no longer about guitars being the best that they could be. It was about them being the most profitable that they could be. And trying to install calibrated pickup sets at the turn of the ’60s - ’70s decades was about as far from CBS and Norlin’s idea of profitability as you could get.

One of the other problems with calibrating matched pickup sets fifty years ago was the very real danger of derailing existing success. By 1970, the guitar manufacturers had seen their designs go in and out of fashion, or flop altogether. And they knew the value of a popular product. They also knew it was incredibly difficult to second-guess what the mass market would accept. If they were going to change the pickup specifications, they were going to change sounds which had become legendary. Hendrix had by that time defined the then modern rock music with stock post-CBS Strats. A sudden decision by Fender managers to re-voice that guitar would not be brave. It would be stupid.


The Fender Jazzmaster, introduced after the Stratocaster, once again drew its individual pickups from universal, uncalibrated stock. This appears to show that there had been no significant criticism of the company's decision to dump position-calibrated pickups. But that may not have been the case. The Jazzmaster's pickups were beefier and thicker-sounding than those on a Strat, and the Jazzmaster allowed the neck pickup to be used with a totally separate set of controls from the bridge. This meant that switching output could be balanced electrically, a la Gibson. Interestingly, the Strat was easily outsold by Jazzmasters and Jaguars prior to the Hendrix era, by which time saturated amps and heavy neck pickup use compensated for the Strat's shortcomings. Did the lack of output compensation on the bridge pickup almost kill the Stratocaster?

MARKET EVOLUTION


But as time moved along, circumstances conspired to render the climate much more compatible with the idea of pickup calibration. Production control became more precise, and the big guitar manufacturers ran into a lot more competition. Ten years on, their sales were being hit from all angles.

There was the increasingly accurate Japanese copy market. There were the patent-dodgers, like Yamaha, whose SG range did exactly what Gibson Les Pauls did, but without infringing any intellectual property. And pertinent to this post, there was the customisation market, which had burgeoned through the 1970s, with more and more guitarists tinkering with their instruments to personalise their sound.

Customisation was really only a progression from what the guitar nerds had been doing in the ‘sixties. The difference ten years later was that retrofitting had become a lot more adventurous, and obvious. Cottage suppliers were making replacement pickups. And if a pro put an obviously alien DiMarzio Super Distortion in their Strat, amateurs were going to notice. That would not likely have been the case in the ‘sixties, when the pro’s had just been switching poor stock pickups for better stock pickups.


The first ventures into 'Superstrat' territory were born amid frustrations with the Stratocaster's perceived "weak back pickup". The classic 1970s remedy was to widen the bridge pickup cavity, mod or replace the scratchplate, and fit a Gibson or DiMarzio humbucker in the back position. There were multiple problems with this, such as the narrower Gibson width which left some strings wide of the poles, but OMG did the idea take off. This mod was a form of calibration, because people were ONLY fitting a humbucker at the bridge.

So with customisation, small demand fuelled small supply, small supply on the big stage fuelled big new interest, and big new interest fuelled big demand. This exploding market actually did what the guitar manufacturers themselves had never been able to do. It let the musicians, en masse, determine design progress. As the 1980s dawned, newer guitar manufacturers were taking their inspiration from that customisation market. Designs like the generic ‘Superstrat’ – based on an extremely popular customisation meme – would make a name for numerous companies, to the direct detriment of both Fender and Gibson’s sales.

Finally, the idea of pickup calibration, or at least the idea of a bridge pickup having different spec from the neck, had proven itself widely popular. And the ‘Superstrat’ concept was selling so well, that Fender could no longer dismiss it as ‘boutique’. By the 1980s it was very, very mainstream, and it was hitting them hard in the pocket. The time had come. You either acknowledged pickup calibration, or those who did acknowledge it, would take your trade.

The course of the 1980s brought a mass acceptance of calibrated pickup sets, and the likes of Fender offered them just as had the ‘boutique’ pickup manufacturers of the late 1970s, themselves now established in the mainstream. Making one design and saying “if you don’t like it, lump it”, was no longer competitive. Companies had to be seen to care about positional compatibility in a pickup. By 1985, when you walked into the guitar store and said you needed a pickup, you could expect to be asked:

"Neck or bridge Sir/Madam?"

DID WE GO TOO FAR?


The idea of calibration was so logical that it wasn’t until quite recently I began to question it. I use a range of guitars with calibrated pickups. And I’ve allowed myself to be governed by that calibration… I also have numerous guitar pickups lying around. Stuff I’ve replaced over the years and have never sold because I’m one of the world’s worst hoarders. Why sell it when you can keep it? That’s my outlook.

And every so often I look through these old pickups and think about putting them back into a guitar. And it’s like…

“Bridge Hot Rails? That’ll have to go in the bridge position. Ah, Cool Rails, that might be better suited to what I’m after… Oh no, but that’s a neck pickup, so I can’t use it in the bridge…”

There I was with all these things that would fit anywhere on the guitar, talking myself out of using them because of what it said on the box. So I took a challenge. Ignore what it says on the box, and switch them round… I put a neck Cool Rails in the bridge, and a bridge Hot Rails in the neck, and sat there tapping the magnets with a screwdriver to see how awful the volume imbalance was going to be once I got the strings on.

Pretty awful, budgeting for the differences in string volume. But I still wanted that relatively ‘bitey’ humbucker at the bridge, and something that could do monster “woman tone”, for want of a better phrase, in the neck. I reminded myself of Andy Summers’ old Telecaster with a humbucker in the neck and a regular single at the bridge, and convinced myself I wasn’t going mad.

Then I had an idea I’d used before to great effect in a Fender Jaguar about thirty years ago. Moderate the volume of the louder pickup with a resistor. Amazing! Neck pickup volume moderated, and the sound is even more bloopy and round than as standard.

Since that experiment, which worked very well, I’ve started to feel that some of the calibrated pickup combinations are a little boring. A bit too perfect. A bit too much like we let science and logic come between us and the excitement of imperfection.

The truth is that there are so many ways we can compensate for volume imbalances (from simple height adjustment, through separate volume circuits and artificial processing such as compression, to wiring a 100K or 150K resistor into the guitar), that we don’t really need to be told by manufacturers where a pickup has to go.

But we should not forget the issue of output balance altogether, as Fender did with the original Strat. True, the Strat is the most popular guitar ever. But it's also overwhelmingly the guitar that has been deemed to need a form of pickup calibration. And it's the guitar that, because of its exposed output discrepancies, almost faded from view. We do need pickup calibration, but we don't need to regard it as a law.