By Dave Lockwood
Electrical noise — hiss, buzz and hum — is something that plagues
every electric guitarist to some degree, but noise comes in a variety of
forms and it is important to establish exactly which kind(s) you are
experiencing in order to devise an appropriate solution. Most noise in
an electric guitar rig emanates from one or more of five different
sources: amplifier self-generated hum and/or hiss; hum or buzz picked up
by the guitar itself; self-generated noise from any pedals/processors
in the circuit; gain structure-related noise, such as cascaded
distortion stages; and ground-loop-related hum. If you think you are
suffering from noise that isn't generated in one of these ways, I'd like
to hear about it!
The most efficient way to track down noise in a guitar system is to
think of the amplifier or studio monitor system as the end of your
signal chain and work systematically back from there. If you don't do
this, you have no idea whether the noise you are hearing from the
amplifier is being generated within the amp itself, or being picked up
by the guitar and fed to the amp. You could end up taking steps to solve
a problem you don't have, as well as completely failing to solve the
one you actually do have. If your amp or monitoring system hums or
buzzes excessively with no input connected to it, then you've got an
equipment malfunction. That is beyond the scope of this article, so for
these purposes I'll assume that that part of your rig is clean. From
here on, I'm also going to treat amps and recording processors (Line 6
Pods and the like) as the same, because it is the 'upstream' noise of
the guitar itself and related systems that we are interested in.
Left:
A small tag of copper foil is used to continue the screening onto the
underside of the shielded scratchplate. Passing one of the scratchplate
screws through it ensures consistent contact.
When tracking down noise it always pays to initially reduce your
system to the minimum number of components, so begin by connecting your
guitar directly to a single amp or recording processor via a screened
cable, set the volume of the amp or monitor system to a normal operating
level, turn the guitar's volume control all the way down and just
listen. If there is any more noise than there was before the guitar was
connected then the cable is at fault. With nothing connected, the amp's
input jack will be automatically short-circuited to ground; with the
guitar connected, but turned down, the input is again shorted, but at
the other end of the cable, so the cable is the only variable.
Assuming all is well with the cable, now turn up the guitar's volume
to maximum, hold the strings in a normal playing fashion and listen
again. If you hear no more noise than before, congratulations; you must
have a fantastically well-screened guitar and the perfect
guitar-recording environment. The rest of us will be hearing at least a
bit of buzzing and maybe a bit of 50/60Hz hum as well. Move the guitar
around over an area of a few feet either way to see if the hum goes
away. The level of hum is usually directly related to the guitar's
proximity to any large mains transformers in the room. If you are using
conventional (non-hum-cancelling) single-coil pickups and you are within
the radiated field of a mains transformer, you will get hum. Exactly
how much depends on the gain in your system and your proximity to the
source. If you can't work out the origin of the hum field, try switching
off everything except your amp (or monitor system, if you are DI'd) and
then switch things back on one at a time to see when the hum reappears.
When it does, see if you can re-site the offending item further away.
The only solution is physical separation, as the amount of additional
screening required to keep induced hum out of the pickups would actually
prevent the guitar working at all. Of course, if you are using
humbucking pickups, you are in the clear on this one, but the chances
are you'll still have some 'buzz'.
Buzz has a lot more high-frequency content than hum. If you are
unsure which you have, try turning your guitar's tone control all the
way down; if the noise mostly goes away, you are dealing with buzz
rather than hum. Buzz will also often be greatly reduced when you touch
the strings or any other metal part of the guitar, sometimes accompanied
by an audible click, whereas hum will remain unchanged. The common
explanation for why noise goes away when you touch the strings or
metalwork is that you are adding to the overall amount of screening. I'm
not so sure about that, because certain types of noise actually get
louder when you hold a guitar close to your body without touching the
strings. This suggests to me that the player's body is, effectively,
conducting the interference into close proximity with the guitar. The
noise goes away when you touch the strings because that interference is
safely conducted away to ground.
Unlike hum, which is generally induced directly into the pickup coils
themselves, buzz gets in everywhere, so any bit of unshielded wiring
can be the source. Even guitars with humbucking pickups will often still
buzz. This is, understandably, very frustrating if you've just shelled
out for a set 'noiseless' pickups for your Strat and find out the
instrument is just as noisy as before; it no longer hums, but the amount
of buzz is unchanged because the noise is getting in via the control
cavity and the unscreened wiring rather than the pickups. The only
answer is to screen every part of the internal electronics with copper
foil or conductive paint, which is then connected to the earth side of
the circuit. Do not attempt to screen the pickups themselves, or even
the pickup covers, however, as this will alter the sound.
'Noiseless'
single-coil pickups, such as these models from Kinman and Dimarzio,
will cancel hum effectively, but noise can still get into the system via
the wiring and controls.
Screening will make a major
improvement, but if you are using single-coils with a high-gain setup or
lots of compression, you will still have some noise pickup. Buzz is
often sensitive to the angle at which you hold the guitar, however, so
you can always try to find the 'null point' at which the noise is least
intrusive and simply do your best to keep the guitar at that angle
whilst recording. It sounds crude, I know, but pro Strat and Tele
players have worked that way in the studio for years because, until
recently, there were no hum-cancelling single-coil pickups that sounded
enough like the real thing to make the trade-off worthwhile.
The most common sources of buzz are TVs and CRT computer monitors,
computers themselves and lighting dimmer switches. Just occasionally
you'll also find a poorly designed external power supply for some piece
of equipment in your rig that puts buzzy noise back onto the mains and
thereby affects everything in the room. So, switch the TV off, use a
flat-screen (non-CRT) monitor if possible, site your computer over four
feet away, dump any noisy PSUs and use only conventional incandescent
lighting.
If you've done all of those things and you've still got a nasty,
edgy-sounding buzz, then the chances are that there is a lighting dimmer
involved somewhere. The trouble is, it doesn't have to be
your
dimmer — lighting dimmers can affect you from an adjacent room, or a
room above or below you. And it doesn't even have to be the dimmer
itself — the cable running between the dimmed lamp and the dimmer
control can also emit interference and this is often routed across the
middle of the room within the ceiling void. Dimmers make most noise when
they are actually dimming, so the noise will improve slightly when you
turn the dimmer all the way up, but only switching it off altogether
will make the interference go away. Dimmers that work on an entirely
different principle and do not create electrical interference are just
starting to appear on the market — watch this space for news.
Over the next few issues we'll tackle sources of noise beyond the guitar itself: pedals, cascading gain stages and earth loops.
Dave Lockwood
If
touching your guitar's metal jack socket when your guitar is connected
to the amp kills the noise, but touching only the strings doesn't, then
you may have a faulty grounding connection inside the guitar. Invariably
there's a wire connected to the back of the pots or the cold side of
the output jack that connects to the bridge directly or via the tremolo
spring anchors, so check that this is intact. If you're not sure, make a
temporary connection with another piece of wire to confirm your
suspicions. Pretty much anything will do. If the hum goes when you fit
your piece of wire, then the existing ground wire is broken or detached
somewhere.
If you hear electrical noise (including crackling) when
you move the tremolo, that's probably because the tremolo springs or
some other non-moving part of the tremolo is grounded, but the strings
are connected to it only via the tremolo pivot points, and if these
don't have a very low electrical resistance at all times, you'll get
noise that will vary as the resistance varies. Spraying a contact
enhancer such as DeOxit on the pivot points can help, but in some
tremolo designs it may be best to use a thin, very flexible wire to
ground the moving part of the tremolo providing you can find or create a
suitable attachment point, such as a tag washer fixed under one of the
existing screws.
You
can combat both hum and buzz in Strat-type guitars by using a
reverse-wound, reverse polarity middle pickup (as the name suggests, the
magnets are the other way up and the coil is wound the opposite way)
and most modern (non-vintage reissue) Strats are now wired this way as
standard.
When used in combination with either of the other
pickups, the RW/RP pickup creates a parallel-connected humbucker. Noise,
which is induced into the coils only, is cancelled out as the two coils
are, effectively, out of phase, whilst the strings are sensed by the
magnets, initially out of phase (due to the reverse polarity of one of
the pickups) and then restored to in-phase by the reverse winding. The
net result is a clean signal with no noise. It works a treat, but only
in switch positions two and four, which, ironically, are the ones that
you would rarely choose for high-gain work.
Effects Pedals
Designed by East Sound Research of Denmark, Carl Martin's Vintage
range of pedals is designed to offer both tonal quality and mechanical
longlevity, hence the chunky cast metalwork, chicken head knobs and
mechanical bypass switches. All three models reviewed can be powered by
means of a standard 9V battery or an external power supply, and the
battery compartment is easily accessible without tools by means of a
lift-out flap on the underside of the case. Rubber feet keep the pedals
from creeping and they're heavy enough to stay put without being too
heavy to carry around in your gig bag. The input and output jacks are on
the edge of the case away from the player.
Finished in surf green, the
Surf Trem (£54.99) is
the simplest of the pedals and has just two controls other than the
mechanical bypass switch and red indicator LED shared by the other
models in the series. This is a straightforward tremolo effect, taken
directly from the Carl Martin Tremovibe, with depth and speed controls
that cover all the range you're ever likely to need. Depth adjusts the
amount by which the level is modulated while Speed sets how fast the
level wobbles. While this pedal doesn't do anything unusual, it does
work extremely smoothly with no obvious noise or unwelcome thumping, and
the bypass switch seems pretty quiet too.
The
Crush Zone
(£54.99) is an old school distortion box with controls for output
level, tone and distortion. It has a raunchy, raspy character
reminiscent of the old MXR Distortion Plus that straddles conventional
overdrive and fuzz. A tone knob can be used to smooth out the tone but
even at the minimum drive setting, you can't really clean up the sound
by backing off the guitar's volume control, so this is definitely a
'step on it and blaze away' kind of pedal. Within its genre, Crush Zone
delivers exactly what is expected of it. It's great for power chords or
solos but is perhaps less well suited to blues or country rock.
There's little detailed technical info on the
Red Repeat
(£79.99). Apparently it was derived from the Carl Martin Delayla pedal
and, from the sound of it, it is either an analogue (charge-coupled
delay line) delay pedal or an extremely good emulation of one. My money
is on true analogue, though none of the available literature comes out
and says it in so many words. In addition to controls for Echo Level,
Time and Repeat (feedback), it also has a tone control that can be used
to darken the sound of the repeats. At long delay times (the longest of
which is 600ms), there is a little background noise in evidence, though
rolling off the top end using the tone control masks this pretty well.
The repeats get darker and grittier each time around, which is actually a
lot more musical than the pristine delays of a standard digital delay
pedal, and at more practical delay times of 400ms or less with just a
bit of top rolled off, the effect is exactly right.
Unlike tape echo units (or their solid-state equivalents), which may
use multiple heads to produce multiple delay taps, this one generates a
single delay that can be made to repeat to a greater or lesser extent
using the Repeat control. If you crank this up too far you get the
familiar swirling, out-of-control effect so beloved of dub producers,
but normally you'd keep away from such extremes. The old analogue delay
sound is definitely something special and the Red Repeat captures it
perfectly.
While these pedals offer nothing radically new, they are sensibly
priced, extremely solidy built and the sounds they produce are exactly
right for their respective genres. It is still worth checking out the
usual suspects such as Boss, especially where distortion is concerned,
as that company offer so many different variants of fuzz, distortion and
overdrive. However, I respect the 'built like a tank', no-nonsense
approach taken here, and I can see no reason why these pedals shouldn't
outlast their owners.
Paul White
SUMMARY: Retro sounds and styling from a well-respected effects designer.
First Line +44 (0)1392 493429.
www.carlmartin.com
