YOU HUM IT, I'LL CANCEL IT! : November 1998
November 2009
| YOU HUM IT, I'LL CANCEL IT!Kinman & Dimarzio Hum-Cancelling Guitar PickupsPublished in SOS November 1998  Printer-friendly versionReviews : Accessory
KINMAN & DIMARZIO HUM-CANCELLING GUITAR PICKUPS Computers may have revolutionised home recording, but for the recording guitarist who prefers the sound of single-coil pickups, they have taken the age-old problem of radiated-field noise to a new level. Dave Lockwood checks out a new generation of pickups promising a real solution without compromising the classic sound. Don't worry. You haven't picked up a guitar magazine by mistake!
There's a perfectly valid reason why this month's Sound On Sound contains a review of guitar pickups. If you happen to fall into
that half of our readership that our reader surveys tell us are
guitar players, then this is one you won't want to miss. The fact
that half of you are guitar players means that, statistically,
something in excess of a quarter of you must be playing a guitar
with single-coil (as opposed to humbucking) pickups on it. In
which case, you will already know that computers and single-coil
pickups don't make particularly good companions in the studio.
If you attempt to use a single-coil pickup, especially with distortion
or compression, anywhere near a computer and monitor, the radiated
field is picked up by the coil at nearly the same level as the
strings, making your guitar totally unusable! Nevertheless, the uniquely bright, 'open' qualities of the single-coil pickup remain as popular as ever, and consequently there have been many attempts over the years to overcome their inherent susceptibility to induced noise. Of course, you can just mount two smaller coils side by side within a Strat-sized casing and achieve a hum-cancelling pickup which still approximates a single-coil tone as a result of sensing a fairly narrow string area -- there are some very nice-sounding pickups which use this method, but no-one would claim that they possess the uniquely airy, open quality of a true single coil (see the 'Genesis of the Humbucker' box, below, for more on this). The second approach is to use a stacked-coil configuration (first patented in 1972), with one coil placed on top of another around a common magnet structure, offering the added benefit to the traditionalist of looking just like a normal single coil. DiMarzio, the American company that practically invented the large-scale replacement pickup market, was one of the first manufacturers to offer a stacked pickup as a standard production model, in the form of their HS (Humbucking Strat) range in the early '80s. However, the HS pickups failed to satisfy most players (Yngwie Malmsteen being a notable exception). The hum cancelling was certainly effective, but the sound was somewhat flat and lifeless, offering neither the tonal sparkle, nor the dynamics of a proper single coil. Even pickup guru Seymour Duncan's stacks were no more convincing, and for many people that was a sign that the principle itself was fundamentally flawed. At this year's NAMM show in Los Angeles, however, there were two new stack designs on offer, both making the usual extravagant claim of sounding "identical to a vintage Strat pickup, without the hum". DiMarzio was championing its Virtual Vintage range, using a distinctive new metal shield on the top coil, whilst Australian pickup designer Chris Kinman debuted his 'AVn' (Authentic Vintage Noiseless) stacked coil pickup, also with an inter-coil shield of intriguing design (for more on the theory behind these pickup designs, see the 'How Stacked-Coil Pickups Work... Nearly' box on page 126). The review models were evaluated by mounting them in turn on the same guitars (Fender USA '62 Re-issue Strat with rosewood board, and Fender 1971 maple-neck Strat), with the results, using a variety of amps and DI processors, being recorded to multitrack digital tape to facilitate direct comparison. SOS Editor Paul White conducted his own listening tests in parallel with mine, mounting the pickups into his Strat Plus (see the 'Second Opinion' box elsewhere in this article). Both manufacturers recommend that to really maximise immunity to noise, you should screen the whole of the control cavity with metal foil or conductive paint. Whilst this is certainly true, the majority of the noise undoubtedly emanates from the pickups themselves, and in the end I chose not to screen the control cavity for the tests as I seriously doubted how many other people would bother, and I felt it was important to establish how well this 'hum-cancelling pickups but unscreened guitar' combination worked. I did, however, take the sensible measure of adopting a shielded output cable from the volume control to the jack socket on the test guitars. The typical 'Fender-type' single-coil guitar pickup is the simplest
electro-magnetic pickup imaginable -- economical, easy to mass
produce, and more than up to the job of producing a simple voltage
analogue of a vibrating metal string. The susceptibility to interference
was always a known limitation, but when they first appeared on
mass-produced electric guitars from the early 1950s, the world
was a considerably less hostile place in terms of stray magnetic
fields and RF emissions. Any hum or buzz that you encountered
when playing a Strat or Tele could usually be alleviated just
by taking one step further away from the source of the problem.
Nevertheless, an electric guitar that did not hum, even when you
sat right next to the amp, was obviously going to offer the manufacturer
a powerful marketing edge, and in 1957 Gibson introduced their
famous 'Humbucking' (or hum-cancelling) pickup. Gibson employee
Seth Lover's design cleverly utilised what was effectively two
single-coil pickups placed side by side, but wired with the two
coils electrically 'out of phase' with one another. The physical
proximity of the two coils meant that any noise current induced
into one coil was certain to be introduced equally, but in opposite
phase into the other, so that it was cancelled out when the two
signals were combined. The wanted signal from the string is not
cancelled out along with the noise because the string's vibration
is sensed not by the coils, but by its disturbance of the field
produced by magnetic polepieces within the coil. The two coils
have polepieces of opposite magnetic polarity, making the signals
induced into them out of phase with each other, a situation neatly
reversed by the 'out of phase' combining of the two coils. The
design results from a delightful piece of lateral thinking which
truly appears to give you something for nothing, especially as
Lover chose to connect the two coils in series, not parallel,
thereby gaining a higher output and further improving signal-to-noise
ratio, as less gain was then needed in the amplifier. The downside was that whilst the coils did not hum, they didn't
sound the same either. With its side-by-side coils, a humbucker
senses a broader area of the vibrating string, and combining the
coils in series raises the inductance and thereby lowers the resonant
frequency of the pickup. The net result was a pickup that was
punchier and darker than the bright, twangy single-coil sound
players and audiences alike were used to, and it was no surprise
that it was jazz and blues players, with their generally more
mellow tonal palette, who took to it first. Only in the mid-'60s,
as the distorted sound of overdriven valve amplifiers became popular,
did the humbucker come to be really appreciated, primarily for
its powerful output. Whilst the die-hard Strat or Tele player
may have looked on with envy at the humbucker's immunity to interference,
most felt the tonal and dynamic compromise to be too great to
justify the benefit. Both ranges of pickups incorporate a number of models; in Kinman's case, these are defined by the year they replicate ('AVn62' and so on). DiMarzio's pickups are distinguished more by function ('Blues', 'Solo' etc). Both ranges offer direct replacement of a stock Fender pickup, with no additional routing or mounting hardware. Like all stacked pickups, they are a hint deeper than a conventional single coil, but not so much so as to cause any mounting difficulty. Virtually Vintage? I was able to test nearly all of the Virtual Vintage models, beginning with the classic stock Fender sound of the DP401. The range consists at present of six models:
DiMarzio supplies installation notes that recommend the use of a 500k(omega) volume pot "for best all-round performance". Don't take this lightly and think that it won't make a difference -- it does. On a 250k(omega) stock Fender (and clones) pot, even the brightest VV sounds a bit flat and lifeless. The installation notes suggest that you can use a 250k(omega) volume in conjunction with a 1M(omega) tone pot to achieve a "warmer, vintage (1950s) response". I have to say that this didn't work for me - I found I needed at least a 500k(omega) and preferably 1M(omega) on the volume control to squeeze the maximum amount of high-end out of all the DiMarzios, and therefore stuck with this setup for the rest of the testing on the VVs. Both these pot values are readily available from guitar parts suppliers or repairers. The Virtual Vintages' immunity to unwanted noise pickup is immediately impressive. With the rest of the guitar unscreened, the VVs' unscreened output leads are the limiting factor, and there is still some noise susceptibility if you get too close to any sources of interference. However, they certainly represent a vast improvement over normal single coils in the studio, in this respect. The sound of the DP402 Virtual Vintage Blues pickup in the bridge position was impressively edgy and responsive, with a healthy dose of that characteristic 'wiriness' that a good Strat must offer. Moving forward to the middle and then the neck pickup, the sound was far more recognisably Strat-like than any stacked pickup I had previously tried, and certainly more so than a side-by-side Strat-sized humbucker. However, the 'in-between' position sounds (ie. bridge and middle, or neck and middle pickups on together) lacked some of the complexity of tone that normally gives these their unique character. Referring back to a real Strat set showed the VVs' combined selections to be both harder and thicker-sounding. The same referral showed the individual pickups, whilst beguilingly sharp, almost glassy, on first listening, to have, in comparison with the real thing, a significantly attenuated high top end. It's almost more Tele than Strat, which can actually be quite useful in the bridge position, but loses some of the essential 'open' character of the other pickup positions. Installing the DP406 '54 Bridge' and DP405 'regular 54' in the middle improved things a touch, bringing back a hint of the characteristically hollow 'cluck' on the 'bridge and middle' combo, but again, reference to the real thing shows it to have a different, darker overall tonal balance. Output on the 54s is roughly comparable to that of a vintage Fender, and on the standard DP401 VV, a touch higher, but there is a hint of reduced dynamics - it just doesn't do as much as a real single coil when you dig in to it hard. Some players could well find this more a benefit than a drawback, particularly in a recording situation, whilst other will be bugged by it - something very much in the realms of individual taste and playing style. In essence, the principle behind the stacked-coil humbucking pickup
is that it relies on only the top coil sensing the string, thereby
producing something like a normal single-coil sound, whilst the
bottom coil only picks up induced noise which is used in antiphase
to cancel the noise also picked up by the top coil. However, in
practice, it is not quite so simple. With both coils in close
proximity and wound around a common magnet structure, interaction
is inevitable, and the simple fact that the two coils are connected
together changes the the DC resistance, altering the inductance,
and thereby the resonant frequency... I could go on, but you've
probably got the point! In spite of the efforts of some very clever
designers over the years, no amount of innovative juggling with
magnet strengths, wire gauges and the number of turns in the coils
has seemed able to produce anything closer to the desired result. The two highly significant differences in this latest generation
of stacked single-coil designs lie in the fact that both the new
DiMarzio and Kinman designs employ dissimilar coils on the top
and bottom of the stack, and both also utilise magnetic shielding
between the two coils to reduce the effects of interaction. In
both designs, the magnets (vintage style, lightly chamfered on
their top edges, configured south pole up), which in previous
stacks passed through both coils, now sit only within the upper
coil. The pickups also have something like the normal DC resistance
of a conventional single-coil pickup (about 6k(omega) for a vintage
Fender, rising to about 7.5 for a 'hot' single coil); however,
the lower coil seems to measure only around 20 percent of the
upper coil, thereby reducing its effect on the overall pickup
when connected to the upper one. What makes this possible is that
the lower coil is wound around its own set of steel rods, making
it into a sufficiently effective inductor to still pick up the
same amount of interference as the upper coil whilst employing
a lower-resistance winding (this is vital in order to achieve
full cancellation when combined in opposite phase). DiMarzio's Virtual Vintage pickups incorporate a 'U' section metallic
shield (partially cut away on the bass side), within which the
upper coil sits. Kinman too shields between the coils, but his
design uses a more open structure for the top coil plus the addition
of a partial bottom coil shield as well. Moving on to the other VV models produced progressively darker, more weighty results. For players using a lot of distortion, the extra output and attenuated high top may prove useful in generating a smoother, more punchy tone. These higher-output VV models are not really all that Strat-like at all, but the sound is certainly a valid alternative to that of a miniature side-by-side humbucker. The DP404 Virtual Vintage Solo (a hefty 8k(omega) on the top coil) could well prove popular with those wanting something to sonically rival a humbucker whilst retaining an almost stock, vintage appearance. Authentically Vintage? Australian pickup designer Chris Kinman's AVn ('Authentic Vintage
noiseless') range also utilises a stacked-coil configuration,
appearing, like the VVs, almost totally conventional with the
cover fitted. The Kinmans will actually take a standard Fender
cover (the DiMarzios are just a shade too fat) if you want to
keep an aged vintage guitar looking as close as possible to original.
The only giveaway, and even then only to the eagle-eyed, is the
unconventional magnet stagger which, like the DiMarzios, has been
compensated for modern string gauges (ie. high D pole, low G and
level B). The Kinman AVn magnets are considerably lower gauss
than a conventional single coil, however, allowing the pickup
to be adjusted much closer to the strings than normal without
producing any unwanted effects -- no reduced sustain, no pitch
warble. There is actually some useful tonal adjustment available
in the height setting (far more than with a conventional pickup),
with the overall character of the sound changing from bright and
wiry at 2mm to a softer, more woody tone at 4.5mm and beyond.
However, output drops off more quickly than normal if you drop
them down too far. Many Strat players involved in recording to any serious degree
have adopted the partial solution to the noise problem of using
a special 'reverse-wound, reverse-polarity' middle pickup (Seymour
Duncan's RP/RW seems to be the most widely available). This allows
the two classic Strat 'combined pickup' sounds -- positions two
and four on a five-way switch (often erroneously referred to as
'out-of-phase') -- to become hum cancelling, without affecting
their sound. The only drawback to this situation is that, when
working in an electronically hostile environment, you are limited
to just those two sounds, and a good Strat, of course, has an
awful lot more to offer than that. The DiMarzios' four-conductor wiring will also allow you to integrate
a single VV (most likely in the bridge position, for high-gain
work) into a guitar which already employs a reverse-wound/reverse-polarity
centre pickup, without losing the hum cancelling you already have
in the combination positions. By moving the tone control connections
to the other side of the pickup selector switch, you can then
use the now-free side to 'auto-tap' the VV pickup in 'position
two' (solder the pickup's series connection to the bridge pickup
position and run a ground wire to the centre pickup position)
so that only the top coil is active, effectively leaving you with
a 'south-up, conventionally wound' coil, which will work fine
in a noise-cancelling combination. Although the AVn pickups are available singly, the Kinman range consists of a number of pre-designated sets (usually with a different bridge p/u selected to balance with the others) to help point the buyer in the right direction: The Kinman sets tested were:
The Kinman models feature a screened single-conductor output cable, and require no change to the 250k(omega) volume or tone pots found on a stock Strat, which keeps the installation job within the DIY domain for more players, and allows you to retain more of your original instrument. With the 'maximum vintage' AVn-56s still making their way over from Australia, I began testing with the HMS-V set, consisting of two AVn-'59s and an AVn-'63. In comparison with the stock reference Strat, the sound was slightly darker, and a touch deeper, but there was an openness about it and a speedy attack that marked it out as totally convincing as a single coil in character. I have to admit that these are the first 'stacks' ever to really make me sit up and take notice -- for once the manufacturer's claims really did seem to have some substance to them. Adjusted up to about 3.5mm from the strings (measured with the string held down at the twelfth fret), the sound from the neck and middle pickups was superbly bell-like -- reminiscent of the highly characteristic sweetness of Seymour Duncan Alnico IIs. The 63 balanced well with the others, and worked well on its own, putting a useful bit of extra grunt into the bridge position. Immunity to noise pickup was spectacular, even without the rest of the guitar being screened (the Kinmans' screened output wire is undoubtedly responsible for this) allowing me to use a high-gain sound whilst sitting directly in front of a 17-inch monitor and with a rack of outboard by my side. Previously, to record with this sound I had to retreat to the far corner of the room and keep the Strat's neck pointed precisely out the window! Even the 'in-between' positions retained enough of the hollow character necessary to make those sounds work properly, but the sweeter, fuller voicing of the pickups doesn't produce quite the same set of cancellations as real single coils, to my ears. Nevertheless, this is a particularly fine-sounding set of pickups, with a valid alternative voicing. The DiMarzios produced a very glassy, lively sound that was initially
quite impressive, but after a short while I realised that the
tonal peaks didn't have quite the same character as the classic
Strat. This became more obvious on the in-between pickup positions
-- these sounded quite different to the real thing, but in their
defence, they're able to produce a very nice, if slightly brash,
jangly sound. The susceptibility to interference was much reduced
compared both to the Lace Sensors fitted as standard to my Strat
Plus and Fender's own single-coil pickups. Like the DiMarzios, the Kinman pickups offer a completely traditional
appearance, apart from the revised polepiece staggering. When
you plug in and play, however, the tonality is so close to what
you'd expect from a regular single-coil Strat pickup that it's
almost difficult to believe that these are humbucking pickups
at all. In fact, the only giveaway is when you suddenly realise
your amp isn't humming any more, and even the computer monitor
isn't giving you any trouble! There's no question that the Kinmans came closest to the traditional
Strat sound as well as providing the best interference immunity.
They have just the right amount of edge and shimmer, and when
you use the 'in-between' pickup positions, the results are authentically
hollow. All the pickups in this review have their positive attributes,
but for sheer authenticity and freedom from noise, the Kinmans
are the clear winners. Paul White Like the Virtual Vintages, the other Kinman sets gradually part company with the goal of directly replicating the vintage Strat tone, getting progressively darker and richer. The low-gauss magnets seem to produce not only the expected longer sustain, but also a noticeably 'creamier' distortion, less ragged at the edges and more focused. The SCn 'hot' bridge pickup is the real star here -- think vintage P90, but with a bit more 'air' in the sound. They are effective, but if you want a darker-voiced Strat, other options have always been available to you. One other point to bear in mind is that Kinman models are optimised for a specific fingerboard radius -- there is a '7-to-12-inch' contour which should be fine for any real Strat, and a flatter '12-to-18-inch' option for modern compound-radius necks. The Ultimate Challenge A good single coil is, in my opinion, the most musically versatile of pickups. It can be sharp, or deep; it can be sweet or nasty; it can respond to your loudest or softest touch. To achieve noise-free operation without destroying these subtle nuances of musicality has always been the ultimate challenge to the pickup designer. To my ears, Chris Kinman has finally achieved that goal, and I have no hesitation in recommending his pickups as the only choice for players who want hum cancelling whilst changing the sound of their Strat as little as possible from its stock pickups. However, I recognise that this may not necessarily be your goal -- thousands of people play Strats, wishing all the while that they had a bit more oomph and worked a bit better with distortion. If you fall into that category, the DiMarzios, with their treble peak occurring further down the spectrum than normal, could well offer precisely the kind of extra punch you are looking for. Few products that I have come across have ever fired my enthusiasm
quite as much as the Kinman AVn56/62s, perhaps as a result of
the 25 or so years I have spent wishing that something like this
existed! These pickups do exactly what Chris Kinman says they
do. The DiMarzios, whilst apparently seeking the same goal, sound
significantly different. As always, let your ears be the judge of what's right for you. At least we Strat
players now have some real choice in this area -- at last, the
future can be noise-free for Fender players too!
Published in SOS November 1998 
| Sunday 8th November 2009 November 2009
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