All About Treble Bleeds
Why use a treble bleed?
A treble bleed circuit prevents treble loss when rolling your guitar's volume cotrol back by adding a small value capacitor in parallel across the in and out lugs of the volume pot, acting as a high pass filter. This filter "passes" some of the high frequencies of the guitar's pickup signal to the output of the volume pot which bypasses the high frequency roll off, or muffled tone, that you hear when you roll the volume knob back. In reality, the capacitor creates a short from input to output on the pot and blocks low frequencies and only passes high frequencies (determined by the capacitor value) through the short.
Typically, but not always, a resistor is added to the capacitor to limit, or "damp" the amount of signal passed through the bleed circuit. The resistor can be added in parallel (Leo Fender's original method), or in series (known as a Kinman mod).
Guitars from Ibanez and Paul Reed Smith use a smaller value capacitor as a bleed with no resistor.
Typically, the larger the value of the capacitor, the more need for a damping resistor because larger value caps introduce more upper high mids, which can be perceived as harsh. The larger the cap value. the larger the amount of the original signal will be bypassing the pot, and this can have an unwanted effect on the volume roll off or taper of the pot, causing it not to turn down properly or "smoothly".
What values should I use?
I see a guy on eBay using charts like the one you see above (generated by a free Microsoft Excel tool called Tone Stack Calculator) to tell you that one his listings is for humbuckers and another one for single coils. I also include a screenshot of these as a secondary picture in the 30+ treble bleed variation listings I run ONLY AS AN EXAMPLE.
Unfortunately, what this other seller isn't telling you is that there are a whole bunch of other inputs used to generate these graphs. When using this tool, you need to input the inductance of the pickups, the exact value of the potentiometers (both volume and tone), the exact value of the tone capacitor, the pickup resistance, how many and which pickups are selected, etc... I have to chuckle (or cringe) when he proclaims that he chooses his component values (which he doesn't identify) because single coils and humbuckers have different resonant frequencies. While it is true, resonant frequency has more to do with tone cap selection, which is totally subjective, than it has to do with treble bleed selection.
This brings us to a very important thought. All of these things have an effect on how the bleed works and how the guitar will sound. The plain truth is that you may or may not like the sound you get without a bit of experimenting.
There are some general guidelines, but everyone's taste and perception are different, as well as everyone's amp and effects rig, settings, cable capacitance, along with the fact that no 2 pickups are necessarily the same resistance or inductance wise.
My view is this:
- Capacitors from 180pf to 330pf are typically used with no damping resistor, and are suited to higher gain styles, although you hear some cool blues, country, and rock stuff played on PRS guitars, which use a 180pf cap. Ibanez has long been using H-S-H and H-S-S pickup configurations with great success using a 330pf cap for both the single coils and humbuckers.
- Fender's setup for Vintage Noiseless pickups is 680pf with a 220k resistor (these pickups use 500k pots). This setup also works with humbuckers. In my opinion, the 220k resistor is quite a large value.
- Capacitors between 470pf and 2200pf (.0022uf) work well for BOTH single coils and humbuckers.
- The higher the cap value, the more upper mids in the signal, and the more of an effect there is on the pot taper, and the more likely it is that you will want to use a damping resistor.
- By far, the most popular value combination is 1000pf (.001uf) with a 100k damping resistor in parallel, which works well for BOTH single coils and humbuckers.
- I have read that you should use a damping resistor approximately one third to one half of the value of the volume pot. While this is a good general range, you may find that a large resistor value nullifies the effect you are after. You really don't want to exceed one half of the pot value.
- The only way to determine whether to add the resistor in parallel or series for any particular setup is to try both before soldering to see which works best for your needs and taste.
- What sounds good to one persons ears and feels good to their fingers may not be good for another person.
I own 56 guitars, and not one of them sounds perfect for all styles on every one of my 20+ amps.
What about the different capacitor types?
Different capacitor types sound different from each other, and will have an effect on the "color" of your tone and the attack of your picking.
A capacitor acts as a filter, and will filter off frequencies at a point determined by the capacitance value. Capacitors also change the phase of the filtered signal slightly depending on what type of dielectric is used. Just like different coffee filter materials make the coffee taste different, different dielectric material also impart a different "flavor" by virtue of the phase misalignment with the unfiltered signal.
Very fast dielectric materials like Mica, Polystyrene, and Polypropylene are used in precision high speed switching circuits because they act very quickly on the signal with little or no phase distortion. These caps will allow a crisp pick attack in guitar circuits, which is great for fast playing styles and allows better note definition when only the highs are colored this way. They aren't typically used in most audio applications because they sound very sterile and cold as coupling caps in amplifiers, which filter at much lower frequencies.
Slower dielectric materials like Mylar, Metalized Film, Ceramic, and Paper In Oil impart a much warmer element that is similar in nature to slight power tube sag to the affected frequencies, and yield a bit slower, smoother pick attack that is great for Blues and Classic Rock. Ceramic caps are fairly neutral sounding and won't change the pick attack much. 225P Orange Drops are a good middle ground between definition and warmth, and Paper In Oil caps can add some missing "squank" to your pick attack.
Experimentation pays off!!!
Remember, in most cases it's pretty easy to attach the bleed to a jumper with alligator clips and experiment BEFORE soldering. You can run some wires out under the pickguard on a strat, maybe not so easy on an ES 335 or jazz box.
Experiment a bit before you solder until you get what you are after.
When you find what works best for your setup, solder it in and you are good to go.
Q: I've purchased these great tb sets before from you & love them & put them on all my guitars. Amazing! However, my stock needs replenishing. However, I didn't realize there was a 150k version. I'm assuming it's brighter, maybe? How would you say it differs/improves on/sounds distinct, etc. from the 220k version?
A: It really depends on how you are wiring them and what the desired effect is. When wired series Kinman style, there are 2 things going on.
For the traditional parallel wiring, 100% of the highs pass and the resistor is really only used to modify the taper (damping).
Wired Kinman style, part of the highs passed are blocked by the resistor in addition to the damping effect.
The higher the resistance of the damping resistor, the higher the resistance to ground is, which makes the taper "louder" and "brighter" at the top end of the taper (towards 10). The higher the cap value, the larger the frequency range passed (more high upper mids in addition to highs).
In the Kinman mod, it's also true that the higher the resistor value, a lesser % of the highs pass through, so it becomes a bit of a balancing act. All very subjective as far as usefulness. That's why it's best to use some alligator clips and evaluate with your own perspective.