By Ed Malaker
Posted 05/23/2025
Question
Hi Humbucker Soup,
I asked a question about this last week on how this mod works. I have another question about the type of capacitor used (film, ceramic, PIO, etc.). For the usual treble mod where the capacitor is in parallel to the signal circuit, it seems that that type of capacitor may not be crucial to the resultant tone as the capacitor is only bleeding part of the signal to ground. For the bass roll off mod, because the signal passes through the capacitor and it is in series, does the type of capacitor, film, ceramic, PIO etc., play a more important role? I.e., in this mod, is one type of capacitor better than the other? I have read that when the forward voltage from the pickup hits the capacitor it opens up from zero. Depending on the material type of the capacitor, the reset to zero can be faster or slower thus affecting the resulting tone (treble or bass). So, when in series, does the forward voltage from the pickup and the capacitor reset to zero vary to the extent that a wider or narrower range of frequencies (from the pickup) are heard from using different capacitor materials? Sorry for the rambling, but hopefully you may have some insight into this. BTW, after looking up the G&L bass mod online I’ve found there is no real reference to the type of capacitor used, only the suggested values. You would have thought that someone like Leo Fender would have researched this, but I have also heard he liked lower cost components in his guitar making!!!
John
Answer
Hello John, great question. The capacitor indeed acts as a filter in the standard tone control, shunting high-end frequencies to ground. In this case, the capacitor’s material type has minimal impact on tone since its main role is determining the cutoff frequency.
However, in a bass roll-off mod, the capacitor is in series with the signal, meaning the entire signal must pass through it. This makes the capacitor characteristics more critical because they might influence the tone. However, since bass roll-off is far less common, there are not enough internet discussions about which is best, so you will need to rely on your ears to really hear if there is any difference and, if so, what is best.
Capacitor properties that might come into play
Dielectric Absorption
Some materials can hold on to a charge momentarily before releasing it, which can subtly affect how fast the capacitor resets to zero. A capacitor with this property might affect transients, potentially softening the attack slightly.
ESR (Equivalent Series Resistance)
Higher ESR can slightly reduce highs and dynamics, but in guitar circuits, any influence will be extremely small.
Microphonics
Some capacitors (e.g., certain ceramics) can introduce noise when mechanically disturbed. It’s not a major concern unless you’re using microphonic caps. You will know you are using one of these if you tap on it with your guitar plugged in and can hear it in your amp. The problem with these is they can introduce noise if your “jumping around” allows other components to bump it while you are playing, which will introduce noise. Other environmental factors might also leak into a microphonic capacitor.
Comparing Capacitor Types
Film Capacitors (Polyester, Polypropylene, Mylar, etc.)
Film capacitors have low dielectric absorption and ESR, making them great for transparent tone shaping. These are likely the most recommended.
Ceramic Capacitors
Ceramic capacitors, especially the extremely common disc-style ceramic capacitors, might have a slightly harsher, less musical tone due to microphonics and inconsistent capacitance.
PIO (Paper in Oil) Capacitors
Some players claim these add a “smoothness” to the signal due to their slower discharge characteristics, but this is more noticeable in tone circuits than in a bass roll-off mod. An expensive PIO capacitor is likely overkill.
Tantalum & Electrolytic Capacitors
We avoid these in guitar circuits because they have polarity and degrade over time.
Does Capacitor Type Really Affect Tone?
In most cases, the value of the capacitor (e.g., 0.001µF to 0.0022µF for bass roll-off mods) makes the biggest difference, not the type. However, if you have golden ears and want maximum clarity, go with a polypropylene film capacitor like an Orange Drop.
What About the G&L Bass Roll-Off Mod?
G&L uses a 0.0022µF cap in series with the pickup. Leo Fender prioritized cost-effectiveness to keep guitars affordable for players, so they likely used whatever was cheap and available (often polyester film caps).
In reality, the difference is subtle at best, especially when the mod is not engaged.
I hope this helps. Let us know if you have any more questions.