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Bypassing "Tone" Knob

Discussion in 'Hardware, Setup & Repair [BG]' started by nerdcore, May 13, 2002.

  1. nerdcore


    May 12, 2002
    I have a Squier P-Bass. I've just added a Quarter Pounder to it and it sounds worlds away from the $100 bass it used to be. I've heard talk of bypassing the Tone circuit, how is this done and what benefits does it yield?

    On a side note, I'm now getting buzzing. I did a straight replacement of the pickups using the existing wires. It is grounded through the bridge. The buzzing stops when I place my hand on the strings or any metal part, such as a knob, so I suspect this is a grounding issue. Should I clip the grounding wire going to the bridge? should I find another way to ground everything?

    Also, would it be beneficial to replace the potentiometers? What values would I need to get?

    I basically want to beef up the circuitry. What can I do?
  2. Have you tried another bass on that amp? Grounding yes, cut the wire definately not. If you have tried other basses and it doesn't happen then we've cancelled out poor earthing in your amp. ;)

    If its the bass then try cleaning up the earth joint with a wire toothbrush. Check the solder connection. If it still does it, i heard a technique to cancel out earth hum in amps, it might be possible to apply it to the earth point in a bass.

    Place a 100 ohm resistor in series with the earth connection. This is like a earth lift or a earth damping technique. Cancels out the oscillations (hum) because (as discussed in another thread) you are grounding one side of a phantom capacitor. So by putting the 100 ohm resistor in, you effectively creat a filter network. And yet you are still earthed properaly as 100 ohms is not the greatest resistance (like a open circuit is infinite resistance and thus you get a shock, with the resistor there is still a path to earth, plus if a fault is present the resistor smokes out so you'd smell it before you got the shock heehee)

    Eh it works for amps, try it with the bass. I may be wrong.. where's Pkr2???????? :p


  3. mchildree

    mchildree Supporting Member

    Sep 4, 2000
    I've done this with a P-bass, and it doesn't yield that much improvement...all you'd be doing is taking a high-pass pot out of the circuit.

    But why do it, really? The P-bass is already a limited animal, tonally, but if you take out that tone pot you're guaranteeing that bass will get 1 tone only. If you find a setting you like, just leave it there. At least then you'll have other sounds available in case you want a more or less agressive sound.
  4. pkr2


    Apr 28, 2000
    coastal N.C.
    Nerdcore, I suggest that you check the simple things first.

    First, and probably most important: check the work that you've done up to this point VERY critically. Check for good solder joints (shiny and smooth).

    Check both the control cavity and bridge ground either with an ohm meter or visually. To check the bridge ground visually, you will have to remove the bridge. It is possible for the wood to become dented where the ground wire contacts the bridge causing a faulty connection. Scrape the wire with a pocket knife till it's shiny and move it over so that the tip of the wire is positioned over "new" wood.
    Do the same with the cavity cover ground wire.

    Check to make sure that the control cavity is shielded either with metallic foil or conductive paint.

    As a "grabbing at straws" check, replace the new pickup with the old one and see if the hum goes away. You don't really have to remove the replacement, just hook the original up outboard. If the hum goes away, I would suspect the replacement PUP. Very unlikely but it's always possible to get a defective new part. If you are using a used PUP, it may have been removed because there was a problem with it.

    Be sure to relace the cavity cover. You can bring the PUP lead out under the edge of the cover. Bring it out as far away from the cover screws as possible so you don't crush the pup wires and don't tighten the screws nearest the wire very tight.

    If none of the above suggestion cure the problem, a ground loop may have been been created. If that is the case, and you can only be sure by using the process of elimenation, I suggest that you take it to a GOOD repair person. Keep in mind that the guy in the music store that does the repairs usually isn't all that sharp on electrical matters.

    Good luck, Pkr2
  5. nerdcore


    May 12, 2002
    Thanks for all the suggestions. I'll do some troubleshooting tonight!
  6. Great advice from Pkr2.

    I entirely agree that ground wires usually do get squashed into the body wood, thus loosing the electrical contact. I've used a small piece of shim brass under a bridge to increase the possible contact surface area. Solder the ground wire to the brass shim then slide it under the bridge before screwing down.

    For control cavity shielding, I've successfully used a graphite loaded spray paint that designed for electrical shielding purposes. Make sure you well mask-off all the areas not to be painted!

  7. if touching the strings stopped the buzzing, then there's definitely a contact between the bridge and the grounding wire isn't there?
  8. Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    As far as bypassing the tone pot, I agree with mchildree. I bypassed both my tone and volume pots (see Chaos Gwar's link) and after about a week of raving about how great it sounded and how happy I was with my "new" tone, I bought new controls and installed them.


  9. do you still have gums?
  10. nerdcore


    May 12, 2002
    Thanks all for the advice. The grounding wire was indeed not making contact. I plan replacing the bridge soon, as a side note.

    The reason I was inquiring about bypassing the tone and volume controls was, I thought the simpler the circuit, the cleaner the signal. I plan on buying better electronics in the future anyways. Thanks again.
  11. Suburban


    Jan 15, 2001
    lower mid Sweden
    Quite the opposite.

    I resoldered my Squier P a few weeks ago, and changed the grounding to a "star-connection", meaning all single grounds go to the output. (Also had to move the capasitor from the volume pot to the tone pot, which made a deal of difference...some sucker didn't know what he was doing there...)
    Anyway, this ground improvement I did, took away all of the noise problem, by closing the circuit (please see the thread "Why wire the wires?" for some physics). Before, I closed the circuit with my fingers, now, the grounding cabl does it. Much nicer.:cool: