As a reference resource, I have collected the treble bleed capacitor and resistor combinations recommended by the the major guitar pickup manufacturers (and some guitar makers too). I am reproducing that list here, with notes based on my research and experience. Enjoy and I hope you find it useful!
The Treble Bleed Modification List
(listed in order of increasing capacitor value, for no other reason than I have to choose something)
NB: Resistors are in parallel with capacitor unless stated otherwise
PRS – 180 pF cap (500 kΩ volume pot, no parallel/series resistor).
Bill Lawrence – 330 pF capacitor & 80 kΩ resistor
Mojo Tone – 471 pF capacitor & 220 kΩ resistor
DiMarzio – 560 pF capacitor & 300 kΩ resistor
John Suhr – 680 pF capacitor & 150kΩ resistor
TV Jones – 1 nF capacitor & 150 kΩ resistor (2 nF cap suggested for 500 kΩ pot, humbucker)
Seymour Duncan – 1 nF capacitor & 100 kΩ resistor
Chris Kinman – 1.2 nF capacitor with 130 kΩ resistor in series!
Lindy Fralin – 2.5 nF capacitor & 200kΩ resistor
If anyone has any other recommendations from other manufacturers to add, feel free to drop me a line and I’ll add it to the list!
1: For capacitor value conversions, 1000 pF (picofarads) = 1 nF (nanofarad) = 0.001 µF (microfarad). For treble bleed mods, very small value caps are used, usually 1000 pF (1 nF) or less. For comparison, the most common capacitors used for tone controls are significantly larger; 0.022 µF and 0.047 µF. (i.e. 22 nF and 47 nF). And yes, it would be much easier if we all just worked in nanofarads.
2: Treble bleed mod can have NO effect on your guitar tone when the volume pot is on 10 as the capacitor (and its resistor if present) are short circuited.
3: Guitars with active pickups or a buffer preamp onboard the guitar do not usually require a treble bleed mod.
4: The simplest treble bleed mod is to use a low value capacitor on it’s own. For many people this may not be particularly satisfactory – the tone of your guitar may become noticeably brighter as you roll down the volume (the opposite of the original problem). However, an advantage of the lone capacitor option is that the taper of the volume pot does not change (i.e. the change in volume across the sweep of the volume pot is unchanged from the stock un-bypassed state).
PRS guitars actually choose this approach, and install a 180 pF bypass cap as standard on many of their guitars (usually with humbuckers and 500 kΩ volume and tone pots).
The Gibson “50’s wiring” can have a similar effect to a lone capacitor (some suggest even more neutral) BUT the effect of the guitars volume and tone controls are now interactive (e.g. the tone control can produce changes in volume) which some people find to be a drawback.
5: Adding a resistor in parallel with a larger value capacitor helps to keep the guitar tone more balanced as the volume pot is decreased and corrects the issue of too much treble from a lone capacitor. The lower the value of this bypass resistor, the less the capacitor passes treble at low volume settings. Conversely, the higher the value of the resistor, the more treble is passed by the capacitor.
However, a parallel resistor affects the taper of the volume pot. This results in a more gradual change of volume across the range of the volume knob (i.e. it will give you less volume change between 10 and 7 and a faster volume change between 1 and 3). Personally, I am long used to this and find un-altered circuits change volume too drastically without it. Volume swells can be less smooth at the lowest numbers on the volume knob, particularly for high gain players. No such thing as a free lunch, eh? Everything is a compromise, all the time.
For those of you who don’t like how the parallel mod affects the volume pot taper, and the volume changes too slowly for your liking, a capacitor and resistor in series (e.g Chris Kinman’s mod) gives a less drastic change in volume taper but the tone of the guitar may change in other ways as the volume pot is turned down. In fact Kinman is the only well known manufacturer recommending a series cap/resistor combination. You may or my not notice much of tonal difference between parallel and series resistors so feel free to experiment and let your ears tell you what works best for you.
6: The capacitor/resistor values that work best for you will depend on your total cable capacitance, which is related to the length of the cable, and the input impedance of the first pedal buffer circuit or amplifier input stage that the cable is connected to. You may have to experiment to achieve what your ears will regard as the perfect combination for your setup. The good news is that most people who are bothered by the loss of treble at lower volume pot settings will be happy with many of the above choices. So, don’t spend too long trying to figure out what the perfect choice might be before trying, just dive in.
Personally, I currently like the DiMarzio values (560 pF & 300 kΩ). With a Planet Waves 10ft cable, depending on which effects pedals I am connected to it is either tonally neutral to my ears or introduces a slight but pleasant increase in brightness at low volume pot settings. In my circuit simulations, this combination also produced the smallest change in volume pot taper of any of the parallel resistor/capacitor combinations.
The TV Jones values (1 nF & 150 kΩ) are recommended by many sources as a good choice for maintaining a consistent resonant peak as volume decreases: e.g. John Hewitt (in his simulation work here); and recommended by the excellent people at Ann Arbor Guitars in their video here. (Incidentally Ann Arbor Guitars have some great videos on their YouTube channel, including this great explanation of treble bleed circuits).
Incidentally these values are sold by Stew Mac as a their “Golden Age Treble Bleed Circuit”. Fender have recently marketed a “Tone Saver” that they claim is not a simple treble bleed circuit but when cut open features, can you guess? Yep, a 1 nF cap and a 130 kΩ resistor in a fancy package that costs 10 times more than the functionally identical Stew Mac product. *rolleyes*
7: Pickup maker Jason Lollar recommends no treble bleed at all but suggests a smaller value tone cap or even Gibson 50’s wiring. He has stated that even with the volume knob on 10 the treble bypass circuit will affect your tone. But that statement is completely contrary to basic electronics knowledge, as the cap/resistor are completely short circuited when the volume is on 10 and therefore cannot have any effect on the circuit!
8: The type/construction of capacitor or resistor you use in passive audio frequency circuit can have NO bearing on the sound of your guitar. Let me repeat that another way – construction of capacitors and resistors will have NO effect on the tone of your guitar. None, Zero, Zip, Nada, Zilch! The only thing that matters is the VALUE of the capacitor or resistor. If the values are identical, your PIOs/Polys/Bumblebees/orange drops etc. will all sound exactly the same. I am not going to argue this point with any one. The basic physics of capacitors, i.e. how we know they work, makes it clear that at audio frequencies this is the only way things can be. This will be the subject a future blog post!
You may have your personal favourites, for whatever reason, and that’s fine, but I assure you that if your brain tells you that you can hear a difference, it’s all down to expectation bias. Blinded A-B testing, e.g. from before-and-after recordings, will convince most people of this quite easily. i.e. when people don’t know what type of capacitor is being used, and are asked to pick which one is which, they are unable to tell the difference between different types (i.e. they get the answer right/wrong as often as randomly picking an answer without listening would produce).
By all means buy whatever components you like and are willing to spend money on if they inspire you to play your guitar more often and get greater enjoyment from your music. Don’t let anyone tell you otherwise! Just don’t believe that you’ll achieve vintage tonal nirvana because you spend too much money on what are, along with resistors, the most basic and cheapest electronic components possible. It’s high time we stopped allowing vendors to sell horribly overpriced components on the basis of mythical characteristics that don’t actually exist. (Yes, Gibson, I’m looking at you with your $100+ for a pair of fake bumblee capacitors. Shameful!)
9: Guitar signals are tiny, the voltages are very small. This means that the voltage rating of the capacitors is of no importance. You can use whatever voltage rating you like but lower the voltage rating caps are usually physically smaller and fit better it tight control cavities.