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A different tone circuit

Discussion in 'Pickups & Electronics [BG]' started by topper, Jul 23, 2005.

  1. Ok, so the standard tone control is treble cut right? It bleeds the high frequencies through the capacitor off to ground. I've got a bass (my first DIY bass) that is really bottom heavy and I've been trying to figure out how to fix this.

    I found an alternate tone diagram via a google search a while back and then lost it. I think I've recreated the general idea here.


    Can anyone tell me if they think this will work? I'm guessing I'd have to use a fairly high value capacitor to get a good range of tones. Any thoughts?
  2. David Wilson

    David Wilson Administrator Staff Member Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    I'm not 100% sure what you're trying to do.
    Your sound with tone control on 'full' really has zero (or minimum) cut being applied. If that sound is too bassy, changing the cap value won't help you IMO.
    What sort of strings are you using? If you're using nickels for example, try steels. What is the pickup in the bass in the bass also?
  3. ddnidd1

    ddnidd1 Supporting Member

    A larger value cap will only increase the amount of highs that are rolled off when you use the tone control, resulting in a 'relatively' more bottom heavy tone.

    One other possibility might be to add a preamp which would offer you the ability to boost highs and attenuate the lows, etc.
  4. Yes it will work, but if you want more treble, you'll need a LOWER value capacitor.
  5. BassikLee

    BassikLee Commercial User

    Feb 13, 2004
    Deltona, FL
    Owner: Brevard Sound Systems
    Unless I am high, and I haven't done anything to make that happen in 15 years, there IS a way to have a bass rolloff that works similar to the trble rolloff of a typical tone control. Look at GL basses. Passive B&T cut controls. How they do it, dunno. Works well too. I have a Tribby 2500. I'd open it up and take a look, but there are just too damn many wires in there. Scares a fella...

  6. ddnidd1

    ddnidd1 Supporting Member

    Yes...you can also use (in a different schematic application) a LARGE size/value capacitor to act as a High Pass Filter where you would tailor the value to rolloff the unwanted low end frequencies. This would be a fixed frequency rolloff. However, for what you would pay for new pickups and also having to Guess what they would sound like, you can buy an on-board preamp and have all kinds of flexibility over tone control.

    There are a number of ways to approach your situation. This suggestion is just one possibility.
  7. seanm

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

    Feb 19, 2004
    Ottawa, Canada
    The following should work, but I have not tried it. I used a 250k pot just because they are common.

    Notice it works just like a treble cut, except that the resistor goes to ground rather than the cap.

    FYI f = 1000 / (6.28 * R * C) where R is in k and C in uF.

    Attached Files:

  8. notduane


    Nov 24, 2000
    FWIW: Here's the tone, bass, and volume control section of an L-2000

    Attached Files:

  9. Thanks for all the tips. A few folks seem to think I'm just looking to change the cap value to get more treble. I'm actually proposing a different kind of tone circuit.

    My idea is that the cap would serve as a high pass filter letting only the higher frequencies through to one side of the pot. The original (very bassy) signal gets routed to the other terminal of the pot. The pot then serves as a means to blend between the original very bass heavy signal and a higher signal that has been filtered by the capacitor.

    Does that make any sense?

    Seanm, that looks like a volume control with a high pass filter on it to me.

    noduane, that "bass" control sort of looks like what I'm after.
  10. notduane


    Nov 24, 2000
    The Fender "TBX" tone control maybe?...

    From GuitarElectronics.com

    - schematic -
  11. The TBX control is sort of what I'm after although I'd never use the treble cut side. From looking at the diagram, one side looks like a standard tone control. The other side is basically a tone control using a resistor instead of a capacitor. I'm not educated enough to figure out why this works.
  12. luknfur


    Jan 14, 2004

    the only time I've really jacked with caps, I had a pair of Bart M34C's in a bass with a Bart 3 band (I think both a TCT and NTMB). The pups were so dark they were useless. For whatever reason I ended up running a passive setup using a '54 Les Paul harness as the basis with two very different cap values on each tone pot, and a switching that ran both inside coils/both ouside coils/and both pups HB. The bass brightened up significantly all around, was all humbucking so dead quiet, and had an amazing array of useful tone options. The preamps did nothing but boost or cut what the pups put out - which was DARK!

    Don't understand electronics but from what I can gather a resistor and capicitor fulfill two different functions. A resistor is designed to maintain a relatively fixed resistance whereas a capacitor is actually a storeage device. To my knowledge they definetly aren't used interchageably in guitar electronics. Aside of on PCB's about the only place I've seen resistors is on mid switches.
  13. seanm

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

    Feb 19, 2004
    Ottawa, Canada
    It is ..... Guess it wouldn't really work since it would affect the volume too much.
  14. Ok, I tried this idea out today. Adjusting the pot had absolutely no effect on the sound. I tried taking the pot out of the circuit entirely and connected the hot wire from my pickup directly to one lead of the capacitor, the other capacitor lead I connected to the tip for the jack.

    I expected the capacitor to work like a high pass filter. It did not. There was no difference in the sound with the capacitor or without it.

    Anyone have any idea why?
  15. luknfur


    Jan 14, 2004

    the first thing that comes to mind is that to A/B anything you really need to be able to do them side by side. In my experience, even the time it takes to flip a switch or swap basses can have an adverse affect and the more time lapse the less valid the A/B is.

    From what I can gather you, you soldered it up with and without the cap and that's really way too much delay for any kind of A/B. That may be of use for a variation that is dramatic but not one that may be significant (one difficult to distinguish yet matters).

    The second thing that comes to mind is that once the capacitor is at maximum storeage, with a steady current it simply functions as a direct circuit.

  16. I think you must be right about this. I thought maybe the cap was bad, but I tried three different caps and then hooked it up as a traditional tone control and could definitely hear the difference.

    As far as switching back and forth, everything was connected with alligator clips so this was pretty quick and there clearly was no change in tone.

    I think my only option is to figure that G&L passive bass cut circuit out. I don't have caps that match (or are even close) for it and it looks like it uses a 1M pot and mine is 500K. I'll probably put this on hold for a while while.
  17. Bongo5


    Jun 29, 2005
    I just took a circuits class... so maybe I can help a little. I don't know much about bass electronics yet, but I'm learning.

    In a simple RC circuit - AC Voltage source, resistor and capacitor, if you measure the voltage across the capacitor, it behaves like a low pass filter. i.e. the voltage is the same as the voltage of the source for low frequencies, zero for extremely high frequencies. The opposite is true when measuring across the resistor - it behaves like a high pass filter, the voltage is the same at high frequencies but not at low ones.

    So, if you switch the position of a resistor (the knob) and the capacitor, you should be able to get the effect you are talking about. I know that bass electronics are more complicated than an RC circuit, but I'm pretty sure the same concept applies here.
  18. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN

    A capacitor by itself will cause no noticeable change in tone. It is the combination of capacitance with resistance that creates a tone control. The pot is the resistance that makes the tone control work.
  19. That explains a lot. So do you have any idea how I would create a passive bass cut control?

    So far two ideas have been advanced:
    Fender TBX Tone Control (http://static.zoovy.com/img/guitarelectronics/-/wdu_sss5l12_02_clapton) looks the easiest, but I don't understand how it would work and I need to isolate just the bass cut. I assume this isn't a standard blend pot.

    The G&L passive tone controls have a bass cut, but this is way over my head. (http://www.talkbass.com/forum/attachment.php?attachmentid=21017)
  20. ddnidd1

    ddnidd1 Supporting Member