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capacitors, clarity and deep bass

Discussion in 'Pickups & Electronics [BG]' started by ::::BASSIST::::, Sep 2, 2005.


  1. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    Well, I just got my upgrade package from warmoth.

    2 x 250k pots
    2 x .022 caps
    2 x .047 caps

    sd quarter pounders

    I bought extra caps to do some experimenting.

    M goal is to get deep/bassy tone with clarity (and i cant overstress clarity). muddyness is not my friend.

    My question is with these caps what is the best combination to achieve this goal?
     
  2. DavePlaysBass

    DavePlaysBass

    Mar 31, 2004
    CO
    Assuming you are setting up a P-bass passive, I would say that a 22nF and 47nF cap will not make much difference until you roll the tone control to the warmest setting. At least that's what the circuit simulator says assuming a 6.4H, 10.5K-ohm pickup.

    The 47nF will be a little better behaved (not as much resonance) but the 22nF will pass more highes with a bit of a resonance peak.

    If you are running passive and want more clarity, you may want to look trying a 10' George L cable or other low capacitance cable of 10' or less (19pF / foot or so). A low cap 10' cable looks like 200pF while a 20' normal cable looks like 1000pF. This capacitance should have more of an impact on your tone than the tone cap (unless you are playing your tone pot all the way down).

    Dave
     
  3. +1 I built a inexpensive, homemade outboard preamp that adds no colour to the bass itsself and its gain is only moderate <6db.

    By using a short patch cable from my bass to the preamp (i'm fixing this to my strap), I can drive virtually any long cable without having the long cable colour my sound.

    End result is clarity.

    I have enough electronic parts for two pre-amps, as soon as I get a push-pull pot (for bypass), I'm building an identical onboard unit for one of my basses.
     
  4. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    currently I am using a 10ft neutrik cable. its suppossed to be high quality. Is it?

    And yes, this a passive p-bass.
     
  5. DavePlaysBass

    DavePlaysBass

    Mar 31, 2004
    CO
    Most instrument cable runs 40 to 50 pF per foot. George L runs about 19 pF per foot. There are some other low cap cables out there but you gotta read the specs. I would guess the neutrik is 40 to 50 pF per foot unless they advertise differently.

    If you can get a cable with 200pF or less, you can pass a lot more highes to your amp. At that point the tone shaping at your amp is as effective as an onboard preamp.

    Dave
     
  6. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    I would also try 0 uF :)

    IMHO deep bass comes more from the amp and cabs. If they can put out deep bass, you will get it.

    For my rock bass I disconnected the tone control completely. I control the tone at the amp and want all the highs I can get. I might cut them at the amp, but I have them to use. For rock I need to be able to cut through at higher volumes.

    I also play old country. These tend to be quieter gigs and I want a very warm sound. This bass does have a tone control with a 0.1 uF cap. I roll off the tone about 33% to 50%.

    For rock I tend to also go through a SansAmp for the SVT type sound. For country, I want it clean clean clean.

    Both are P basses.

    YMMV.
     
  7. DavePlaysBass

    DavePlaysBass

    Mar 31, 2004
    CO
    The simulator says....

    Pulling the tone pot and cap will result in a 7 dB resonant boost around 2kHz and then rolls off (-6dB at 3kHz). Both circuits roll off the same but the tone pot configuration has a softer resonant peak at 2kHz of 3 dB. This is assuming you are using a 20' 1000pF cable.

    If you go with a 200pF cable, the standard tone pot configuration (47nF, 250K) rolls off without any resonance and passes a lot of highes (-6dB at 6kHz). The no tone pot configuration has a 3dB resonance around 4kHz at then rolls off (-6dB at 7Khz).

    Dave
     
  8. Wow! I can actually HEAR it! :bag:
     
  9. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    What are your assumptions about the pickup? I am using Quarter Pounders in the rock bass.
     
  10. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    Memphis
    Dumb moment deleted.
     
  11. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    Memphis
    I wouldn't suggest QPs to someone looking for clarity. They run towards the dark (but agressive) end of things.

    But a P Bass isn't about clarity - it's about musical humps in the midrange response. It won't give you a ton of highs and lows, but it will give interesting upper and lower mids (the low mids of a good P Bass) coincide with the lowest frequencies most car speakers will reproduce, and the lowest frequencies most listening environments will support, so you hear it as "a ton of lows" but really it's just the prominence of low mids.
     
  12. DavePlaysBass

    DavePlaysBass

    Mar 31, 2004
    CO
    For a P pickup I am using 6.4H and 10.5k which are what I found on the Fender website for P aftermarket pickups. Different P pups may have varying numbers but things should stay in the ball park and the cause and effect should be the close.

    Resonants created by an inductor (L) and capacitor (C)P vary by a square root relation. Meaning doubling or halving inductance 2 results in a frequency shift of 1.4.

    Dave
     
  13. DavePlaysBass

    DavePlaysBass

    Mar 31, 2004
    CO
    I think your numbers are off.

    Google on "instrument cable capacitance pF".

    At 2000pF per foot, a 20' cable would completely choke the signal coming from any passive instrument. That would be 40nF on a 20' cable. Equivalent to the tone caps.

    Here are some links regarding cap / ft.

    Stompin Ground

    At the Belden site select "Brilliance Broadcast", then select "Microphone and Instrument Cable", then select "Single Conductor High Impedence Cable". Part Number 9395 is an 18AWG center condutor which is typical of what I have used for instrument cables. Belden calls it 55 pF / foot.

    Belden

    There are two ways to decrease capacitance in a coxial shaped cable. The first way is to change the insulation material between the center conductor and shield so it has a lower dielectric constant. This can cost money if the materials selected are exotic or not used in high volume MFG. A second way is to change the spacing between the center conductor and the shield. This can be achieved by using a smaller center conductor (i.e. 24AWG instead of 18AWG) and using more insulation material so the shield is farther away the cable is bigger. I believe George L uses the first approach given the small diameter of his cables.

    I was involved in the design of a steel jacketed coax cable that was used to connect a Turbine ignition box to the spark plug (called an igniter in Turbines). The cable was responsible for conducting a 20kV, 50usec, 2000A pulse. Needless to say the coax characterisitcs were crucial to maintaining performance with cables ranging from 10' to 30'.

    Dave
     
  14. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    +1 I use the QPs for my rock bass for exactly the reasons you mention.For a P pickup I am using 6.4H and 10.5k which are what

    Thanks.
     
  15. Lyle Caldwell

    Lyle Caldwell

    Sep 7, 2004
    Memphis
    Holy smokes, you're right. This is what I get when I post when sleepy.

    Had a huge argument about this a few weeks ago in another forum, and I misremembered things a bit. The capacitance ranges I listed were for total cable length, not per foot.

    I don't know what I was thinking last night.
     
  16. DavePlaysBass

    DavePlaysBass

    Mar 31, 2004
    CO
    When it comes to pickup winding more turns equals stronger signal which is desired but also results in higher inductance which tends to results in less clarity. So like everything there is a trade off. Magnet materials can play a big part in all of this as well.

    If you use an onboard preamp or low capacitance cable, you can get more clarity out of the hotter pickups. If you look at the typical passive arrangement that the great Leo made standard 50 years ago, there are some places to optimize for clarity sake and I personally would not limit my thinking to what the status quo defines as typical. Leo certainly didn't.

    Of course there is also the frequency response of the pickups themselves independent of the electrical circuit. Predicting that is a bit more complex... More turns on the pickup will also limit the pup itself. I personally do not know what the self resonance of a pickup is? Maybe I should take one to work and try to figure it out.

    Anyone know where I can buy a Jazz Bass pickup kit? I have seen some wind your own for guitar pups. I could emerse myself in geekdom for hours with some bobbins, some magnets, and a network analyzer...

    Dave