Treble Bleed Circuits Explained! What is it and why I want it!
Have you ever noticed that when you turn down the volume on your guitar or bass that your signal loses some top end treble and begins to sound muddy, dark and lifeless? Many guitarists resort to using the volume knob as a simple way to mute their guitar. Personally, we like to use it to control the amount of gain in our signal. This allows us to go from crystal clear clean tones to full overdrive with the sweep of just the guitar volume control.
What causes the loss in treble when we turn down the volume knob on our guitars?
When the volume pot is raised or lowered from “0-10’, resistance is added in series with the signal output of the pickup. This resistance, combined with the cable capacitance, and the pickup itself forms a low pass filter, allowing lower frequencies through but blocking some of the higher frequencies. The resultant tone for most people can become unusable or unpleasant.
There is a simple and very easy fix for this problem, and it is well worth doing. The solution is to install a treble bleed circuit into your guitar's existing electronics, which can be either a single capacitor or a combination of a capacitor and a small resistor. A capacitor wired in parallel with the terminals on your volume pot will allow the high frequencies back through when the volume is reduced. The capacitance value of the capacitor will determine the cut off point for the frequencies allowed through. Wiring a resistor in series or parallel with the capacitor will help to control the brightness. To install this circuit yourself you will need some basic tools, a soldering iron, solder, the necessary components and the confidence to use them. If you are not confident in performing your own guitar modifications, contact us at HGWFxPedals .com and we can handle it for you at minimal cost.
Why don’t guitars have treble bleed circuits installed from the factory?
Good question! More often than not its due to a lack of knowledge when the original guitar circuits were designed as well as cost cutting measures. Alternatively the idea is “why bother now when they can sell it for a high price as a separate aftermarket option” There are a few exceptions, but American manufacturers have yet to make it a standard feature whereas some smarter Asian manufacturers now install it as standard in many of their guitars.
What do I need?- Different guitars will require different value components in their treble bleed circuits mainly due to the difference in their pickups. Determining which components to use in some cases can require some trial and error with different value capacitors and resistors until you get a result that sounds good to you. Here I will show some of the different circuits and component values used, to guide you in the right direction.
The simplest treble bleed circuit is a single capacitor wired across two of the terminals of the volume potentiometer.
Pros: It is all that is needed for some guitars.
Cons: There isn’t enough attenuation of the high frequencies and the signal can become too bright and tinny as the volume is reduced.
Wiring a resistor in parallel with the capacitor will help to balance the signal. As you reduce the volume, the higher frequencies don’t dominate. The problem with this circuit is that it affects the taper of the volume pot in a negative way.
Pros: It works on most guitars.
Cons: Changes the taper of the volume pot. Requires correct value to components to work properly.
Series Capacitor/Resistor (Kinman circuit)
This circuit consists of a capacitor wired with a resistor in series. This configuration became popular in the ’90s when Australian luthier Chris Kinman started to use a capacitor and resistor in series for his guitars. Regarded by many to be the best of the three versions, because it solves the problem of the volume taper and the tinny sound.
Pros: Solves the volume taper and tinny tone issues.
Cons: Requires correct value to components to work properly.
Component types and common values
Capacitors store electrical energy, and their ability to store energy (capacitance) is measured in Farads. Now a 1 Farad capacitor would be a very large capacitor indeed. Most capacitors used in electrical circuits are measured in Microfarads with a 1 mF capacitor being equal to 0.001 Farads. For our circuit we require even smaller capacitors with capacitance values measured in Picofarads. 1 Picofarad is equal to 0.000000000001 F. Yes, it’s tiny. Values to try for this application range from 220 pF up to 1500 pF with 1000 pF being the most common.
Capacitors also have different voltage ratings. We need not concern ourselves with that, the signal from a guitar pickup is measured in millivolts. There are many types of capacitors available including: electrolytic, ceramic, mylar film, paper, mica and so on. Electrolytic capacitors are not suitable for treble bleeds circuits. Ceramic or film are ideal and the smaller the better, we don’t exactly have a lot of space in our control cavities.
A mylar film capacitor (left) and a ceramic capacitor (right).
Several types or composition resistors.
Resistors are components which resist the flow of electrical current. When used in a treble bleed circuit they attenuate the high frequencies to keep the signal frequency balanced. Again, we don’t need physically large components. 0.25-watt resistors are just right. The unit of electrical resistance is the Ohm. For our purposes we would use a resistor ranging from 100 k-ohm up to 330 k-ohm.
Time to Experiment?
If you decide to conduct your own treble bleed experiments, solder two wires to the input and output of the volume pot and connect alligator clips on the other ends. If you let the two wires hang out from under the pickguard, you can easily try every combination of capacitor and resistor and see which sound right to you. Remember, tone is subjective, what works for you might not work for another.
Should you decide that a treble bleed circuit is for you, remember this: The modification is completely reversible, once installed it will not affect the tone of your guitar when the volume pot is turned all the way up (max volume). Basses and guitars with onboard active circuits do not need treble bleed circuits. The series combination of 1000 pF capacitor and 150 k-ohm resistor are recommended by many sources as a good choice for maintaining a consistent resonant peak as volume decreases.