Whenever we play guitar with somebody else, we want to be audible. Not just for the other guy (or guys) we play with or even the audience, but also for ourselves. Having huge amounts of low end might swamp our guitar because the bass guitar has much more lows, and having a lot of highs and nothing else will get in the way the crash of the drums and the vocals. Not to mention, those sounds sound just terrible!
To negate those problems and remain audible, we want to cut through the mix, as they say. That means having a sound with enough clarity, bite, presence, treble detail and mids; those tonal attributes cut through some parts of the mix and waltz over others. To attain this goal we get guitars that are constructed in a way to make sure we cut through the mix, we tweak our amps and pickups and sometimes go deeper in changing the wiring, like pots, capacitors, additional resistors etcetera etcetera.
But sometimes this can be too much. Sometimes you have so much clarity it borders on bright, and this line is sometimes even being crossed, resulting in guitars that are simply icepicky harsh. We have discussed a way of getting rid of some of the highs in the article concerning potentiometers, but in this article I want to explore the subject of treble bleeding even further. I want to take a look at the various ways you can reduce the highs and how they affect your tone. As the proverbial icing on the cake, I will take a look at Eddy Currents (electrical whirlpools in metal) and how they affect your tone and how they work with your pickups.
Tweaking your pots
The easiest way to tame the highs is to lower the value of the pots. By lowering the value of the tone pot you change the way the tone pot works, so you don’t necessarily tame the highs when you run all pots on 10. By lowering the value of the volume pot you do change the tone directly. How this works was described in the article concerning potentiometers in general.
Changing the baseplate of your humbucker.
Humbuckers have their bobbins fixed on a metal plate, called the baseplate. If you have a brass plate (which is not a material used by Seymour Duncan) you can swap the base plate with some tweaking, screwing and soldering, for a nickel silver specimen. This will clear up the tone of your pickup. I have done this myself several times with good results. You won’t get a lot of clarity, but it can be just enough to make a difference for you. Conversely, you can swap out your nickel silver plate for a brass one to subtly warm things up. This trick does not work on single coils, of course. Single coils are constructed in a completely different way and are less tweakable than humbuckers.
If you use a plastic pickguard and you need more warmth but with a slightly dirty bite to it, you could consider swapping the pickguard for a metal version. On selected guitars I use a brass pickguard and an aluminium pickguard. The brass pickguard attenuates less highs than the aluminium pickguard, or at least, so it would seem. The difference with plastic, celluloid or even bakelite is dramatic. The output seems to be a bit less with a metal pick guard. Presence and treble seem to be less too, but I get the feeling that the metal pickguard gives the tone a bit of a boost in attitude. More raunchy, dirty and nasty.
But how can a metal piece make such a huge difference? The pickguard is not attached to any part of the electric circuit; only the pickups are hanging in the guards. The reason the pickguard makes a difference is the same reason why attaching a brass plate on the bottom of a Strat single coil gives you more bite and edge and a little drop in the mids. It’s the Eddy currents at play!
Eddy currents are a reaction to a changing magnetic field in a conductor.
Let’s reevaluate this phrase. If you have a metal area and a magnetic field that changes, there will be small currents created in the metal object, perpendicular to it’s surface. These currents are called Eddy Currents because they (electromagnetically) look like eddys in the ocean. These Eddy Currents create a magnetic force of themselves (which is Faraday’s law), which work against the initial magnet that creates the Eddy Currents in the first place.
This is not self inductance, in case you were wondering! Self inductance is a reaction of the coil to the current that’s being created inside the coil when it’s subjected to a changing magnetic field; hence it’s being called self inductance. This happens in every electromagnetic pickup and has to be kept in mind by the pickup designer. Unfortunately, not much can be done against self inductance. A healthy awareness of it can never hurt, though.
No matter how useful they are in other daily life applications, Eddy Currents are incredibly annoying for us guitar players. We notice them as a loss of higher frequencies. Some materials create more of those Eddy Currents than other materials. Plastic is not conductive, so it doesn’t create currents. Aluminium is more prone to creating Eddy Currents than brass, which results in less output of your pickup and less highs.
Back to swapping base plates: changing a brass plate for nickel silver doesn’t just affect the tone, but the output too.
So, changing the value of the pot, changing the baseplate and changing a plastic pickguard to a metal specimen are some ways of taming extravagant highs of your guitar. Where the first works on a direct level of the pickup, the other two work because they change the magnetic field in some way; courtesy of Eddy Currents.