what capacitor for a p bass?

Discussion in 'Pickups & Electronics [BG]' started by vindy500, Sep 18, 2006.

  1. Ezbass


    Apr 3, 2008
    0.1uf on a 250k pot. Most responsive tone control I've ever used.
  2. That's a really interesting model of how things might work, but nothing I've tried seems to follows that pattern. From what I've tried (various caps played back-to-back via aligator clips coming from the tone control) the picture might be more like this: if you take a sharp knife and press the blade into a chunk of wax, both the knife (signal filtered by the capacitor) and the wax impression (remaining signal) are "sharp". I wouldn't pretend to understand the science, but my sense is that a tone circuit acts more like a resonating unit with lots of interplay between the pieces (signal, cap, ground), rather than a discreet, perfect, on/off filter.
  3. Very, very interesting thread.

    I've always wanted to try out some expensive electronic components after reading this article. http://www.parkerguitars.com/forum/post.asp?method=TopicQuote&TOPIC_ID=4640&FORUM_ID=9

    The author recommends a "Jensen copper foil paper in oil," and says that "the Jensen's are very rich sounding and smooth."

    Having always been paranoid that I wasn't getting the best out of my bass (which has already been upgraded with CTS/orange drop), I've wondered what high-end alternatives were possible.

    Wonder if it'll hurt to take the plunge and splurge a bit? :D
  4. I'm running both .1 and .022 caps in my P-Bass and I switch them via a DPDT submini switch. I love the low-end rumble from the .1 and the highs from the .022, it's a very versatile setup. I use $1.50 Radio Shack green caps, they sound great, are a bargain to boot, and I'm real happy with them. I'm sure caps costing ten times as much wouldn't sound any better, IMO.
  5. I've been pondering doing that exact mod.
    is that a three way switch? is one position full on?
  6. void


    Aug 27, 2003
    You might be right that the capacitor acts more like a resonation unit. It's not the same as a resistor which bleeds off part of the signal.
    But a capacitor that's in series with the signal still behaves more or less opposite from parallel with the signal. A small capacitor in series is a highpass filter, a small capacitor parallel is a lowpass filter.

    However that's all theory. Listening is the only way to be sure of the results, and you did that. Trusting your ears is much more valuable than trusting words.
  7. Interesting thread.

    I'm with Rodent on this one.

    When the capacitor is not in series with the circuit the tone you hear does not pass through it. A couple of people have said that it does effect the signal path bc of what it subtracts but I disagree. A "good" or "bad" capacitor should 'subtract' exactly the same thing as long as their value is the same. It doesn't filter out the "good" or "bad" tone. it just effects the purity of the signal passing through it (to ground).

    Another thing I've been thinking is that the tolerance of the cap is IMO very much overrated. a Cap with a J value (manufacturers tolerance rating) will likely be more accurate to the desired value than one with a K rating. Thats not to say that a specific cap might have a value closer to the J one. ie: test 10 K-rated caps and you will find one that is precise.

    That said- When you're tossing up between using a .022 and a .047 who's to say that a bogus .022 'K' that measures at .025 isn't EXACTLY what you're looking for?
  8. It's not a 3-way, there's no full-on position. It's either the .1 or the .022. This is the switch I got at Radio Shack:

    This thread explains how to wire it:

    It's a fairly easy mod to do. The hardest thing for me was finagleing things around in the control cavity, I've got the regular-sizes CTS pots in there. Wish I had the mini-pots, would have been a bit easier to wire up. But no matter, it works fine.
  9. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    The pot and cap form an RC network, which is a low pass filter, so some of the high frequencies are bled to ground, even with the control on 10.

    If you had just a pot (resistance), with no cap (such as a volume control) you have a percentage of all frequencies bled to ground.

    Caps have other properties besides capacitance, such as ESR (equivalent series resistance), internal leakage of charge, series inductance, etc., so different caps will indeed effect the circuit in different ways.

    Cheaper caps such as ceramics are also microphonic, and have pretty loose tolerance, so the rated value might not be what you are getting at all.
  10. Trying to understand how complex things work is often frustrating, probably b/c we often like to have clear answers that never fail. Unfortunately, models/theories are by definition imperfect. They might help us understand, generally, how something works, but by simplifying things to a point that we can get our head around the answer, they leave things out.

    Here's one idea that might help here. I've been doing some studying on how tube amplifiers work and was having a lot of trouble getting a useful picture in my mind of how current flows through the circuit. Most of the discussion and explanations depict current as flowing in a precise, linear way, from point A to point B to point C, etc. And this is reasonable when you are starting out - breaking things down to a point where you at least have some building blocks of understanding to work with. But, the simplification also loses sight of some of the larger complexity.

    What I eventually came to understand is that an amplifier circuit, overall, can be thought of as something like a pool of water: we switch on the power (hose) and current (water) flows into the circuit (pool), and fills it up until the back pressure of the circuit (pool) causes the flow to stop. When we plug in our guitar.... WAIT, WAIT!!!... I mean when we plug in our BASS - whew! - and hit a note, we essentially upset the smooth surface of the pool with a wave that ripples across the circuit and out the speaker. I find it more helpful to think of a tone circuit this way b/c you can imagine how a multitude of extraneous factors beyond the circuit's design - capacitor types, wire pathways, tube manufacturer (the topography of the pool's floor, the temperature of the water, the altitude of the pool) might have some effect on the ripple as it spreads across the pool.

    In the case of our simple passive bass tone circuit made up of just a tone pot (resistor), capacitor, and a few lengths of wire, you can imagine how the capacitor might play a significant overall role. And as SGD Lutherie suggests, the capacitor's other properties, determined by the specifics of it's internal makeup, might come into play.

    But, as they say, the proof is in the pudding. It's true that every cap, regardless of type, age, mojo, whatever - will have one clear effect on tone: it will bleed treble from the signal. But the quality of the filtered signal is more complex than just how much treble is removed. In trying different capacitor types of the same value, to my ear there can be truly significant differences in tone quality - i.e. those less easily described attributes we struggle to find meaningful names for: warmth, roundness, tightness, harmonics, openness, focus, etc.
    Jayneck Peabody likes this.
  11. void


    Aug 27, 2003
    Each capacitor has it's own tonal character mainly because it's not linear across the frequencyband. Some frequencies are filtered more than others, the phase of some frequencies are shifted more than others.

    Everything matters, you can hear differences between different foil materials, dielectric materials, construction, housing, etc.
    If you compare 2 capacitors of exactly the same brand and type, with the same capacity, but only with a different max. volatge rating (which means slightly thicker foil), you'll hear a tonal difference. Thicker foil will give a more pronounced bass performance when used in series with the signal.
    imabuddha likes this.
  12. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Well said. I couldn't think of the word linear when I was posting!

    Obviously the differences are small when used as a tone control, so you might hear it, and you might not.

    Here's an interesting web page with tone cap tests and graphs.

  13. Turnaround

    Turnaround Commercial User

    May 6, 2004
    Toronto Canada
    Independent Instrument Technician
    I guess I'm in the minority here. I changed the stock.047 mfd cap in my P-bass to a .01

    To me the .047 was killing way too much mid and upper frequencies, and when engaged beyond about 30% just made the bass muddy. With the .01 cap, I can reduce finger squeak and nasty highs without destroying the clarity of the instrument.

    Anyone else do this?
  14. Same experience here: a .047uF Orange Drop sounded pretty muddy to my ear on the low settings and also had limited effect until turned down below 40%. With the 0.1uF I am using (pulled out of an old 60's Kay guitar), the tone control now has a more even effect across the entire pot range, and the bottom range (especially 10%-30%) sounds deep but not muddy.

    I would guess Fender moved from 0.1uF to .05uF based on the change over time from Jamerson/Dunn era tones to more modern pick & slap tones. I find that .05uF works well if you want very fine control over the high end, but 0.1uF gives more even control across the range, and especially provides more variety of deeper tones.
  15. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Count me in. I use .01 or .02 for my passive basses. It rolls off the top end and leaves all the midrange. That's where your punch comes from.

    I hear many younger players using the "wrong" tone when they are trying to sound "vintage". It's all bottom end, like you'd use playing dub. I saw Nikka Costa recently, and they went with this whole 70's soul/funk vibe, but the bass was just a muddy blur. The "real" tone had plenty of mids and highs, but had a short decay. You can really hear the thud of the flats when you have a full range tone. Even Jamerson got a good amount of high end in his tone. He just had a lot of sponge under the strings.
  16. DavePlaysBass


    Mar 31, 2004
    I have a 0.1uF (0.1MFD) in my P bass which is what used to be done in the 50's. I like it better than the 0.047uF in my jazz basses.