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Stacked volumes WITH resistors.

Discussion in 'Pickups & Electronics [BG]' started by newbold, Jan 20, 2012.

  1. newbold


    Sep 21, 2008
    A few questions:

    1. Will any pedal buffers between a bass with classic stacked controls with resistors interact with the way the electronics work together or with a valve/tube amp?

    I ask this because I gather from reading that some preamps work 'better' with a bit of resistance and that is a big part of the vintage vibe and tone these controls have.

    2. is a series/parallel mini toggle possible to add to this configuration?

    I have never seen anyone discussing resistors in a p-bass or with series config but if it is possible, I can only presume that only one resistor would be used (they'd interact, no?)...but if the resistors do more for the setup than prevent interaction, perhaps it would be worth including across the board.

    Thanks for any insight y'all have for this guy.
  2. I don't know exactly what you are asking.

    The resistors used on early stacked knob Jazz basses were there to "isolate" the two pickup circuits from each other by placing resistance between them, so that the tone controls would not interact.
    The major disadvantage is that the resistors, being placed in series with the signal path, killed output/treble. It's the equivalent of rolling a volume pot down about a fifth of the way (Assuming an audio taper.), but leaving the ground off.

    If there is only one pickup, such as on a P bass, there is no reason you would want to kill your signal, and there can be only one tone control for the one pickup.
    When you run two pickups in series, you only get one volume and one tone, because the two pickups become as one in the circuit. If you want individual volumes/tones, that takes special multi-pole switch wiring, but one tone pot has to function as a master no matter what you do.

    The other thing the resistors do is give a slight increase in output impedance, but this should not be desirable. You usually want to keep your output impedance low. Furthermore, to some degree, you are increasing thermal noise, as thermal noise is proportional to resistance.
  3. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    What do you call "vintage vibe"? Dark? That's why Fender stopped making the Jazz bass that way. It's dull sounding.

    Having a buffer between the bass and the amp is a good thing, if you want to preserve the sound of the bass.

    Both active and passive basses work just fine with tube amps. Active, or buffered basses might sound a little brighter and clearer. People who are looking for a muddy tone, thinking that's vintage, or are over driving the amp and want a darker distorted tone tends to not like active basses.
  4. pacojas

    pacojas "FYYA BUN"

    Oct 11, 2009
    isolating stacked V/T controls is a huge mistake, IMHO!!!

    carry on, :bag:
  5. +1. Don't know why anyone does it. Fender stopped doing it a long time ago.
  6. newbold


    Sep 21, 2008
    I would like the volume controls to not interact but would also like to be able to get the resistors out of the path at the flick of a switch and have the pickups summed in series.

    I usually have my tone control rolled off a bit and tend to prefer passive electronics.

    If I have series, parallel with, and parallel without resistors going through a 3 way mini toggle, would I run into any problems with the resistors loading the circuit?

    in this link, you'll read that

    " the presence of the resistors has the advantage of preloading the front end of a valve amp,something that valve amps like a lot.
    Even with the volumes rolled right off the amp sees 440k.
    Bear in mind that Leo Fender designed his instruments to work with his amplifiers,for best sound and results.
    And ever since,half the world has been copying his amp thinking,or using it as a yardstick by which others are judged..."


    I'm not trying to debate here. I trust and respect you guys and appreciate the time you put into reading my posts and helping us out around here.

    I merely would like to be able to have the non-interacting controls, interacting controls, and a series configuration.

    If there's a chance that the resistors work well with tubes because of 440k worth of resistance then so be it.

    I'd still like to know if a buffer would either counteract that resistance, presuming uncle stack-knob is right about that.
  7. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Why do you want the resistors? What do you think they will do? They were put there to try and isolate the two tone controls. But it doesn't work well so Leo changed the design.

    You will get lower output with the resistors. That's about it. Just turn down your volume controls for the same affect.

    The stack knob basses were darker sounding because they had four pots in parallel. When tone pots are on 10, the impedance of the cap is less than the resistance of the pot. So it's like another volume control on 10. Four 250k pots in parallel is 62.5k! That made the tone darker than a regular Jazz bass. Jaco's bass was a stack knob and he changed it.

    If you want a darker tone, turn your tone control down more.

    That's a bunch of hooey. The people posting there do not understand how things work. Amps have a pretty high input impedance, especially tubes. They don't "see" any loading. The bass sees loading from the resistors, and they raise the output impedance of the bass. The loading rolls off high end and makes the tone darker. If you like that tone, then fine. But it does not make tube amps work better or any of that nonsense. Also the resistors are not in series, so the amp the load is not 440k. A 440k resistor in series with your signal is almost the same as turning your volume control about half way down. The two pickups, along with the resistors are in parallel. Two 220k resistors in parallel is 110k.

    I have a Mesa 400+ tube amp, and I use active basses with it. It sounds just fine.
  8. newbold


    Sep 21, 2008
    If it's the ONLY option then I think it could be a mistake, but I can't say it's a mistake just yet. Unless it could actually wreck my amp it'd be a mistake.

    I find that my bass sounds a lot differently when my volume and tones are turned down but my volume's compensated for.

    If it winds up being a tone control and slight pad then maybe the switch could come in handy but if the loading changes my tone beyond that I might like it.
  9. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    How would it wreck your amp? No bass can wreck an amp.

    That's because when the volume is turned down a little, you have decreased the resistance between the pickup and ground, thus loading it down, and increased the series resistance between the pickup and amp. These two things lower the frequency of, and flatten the resonant peak of the pickup.

    If your tone is turned down a little, it does what tone controls do, it rolls off some high end.
    You might. You can get similar results using small value caps between the signal and ground, and even resistors to increase loading.

    But all that stuff about "pre loading" a tube amp is gibberish.
  10. newbold


    Sep 21, 2008
    re: loading a tube amp - understood.

    As far as the resistors being there to reduce the interaction between the tone controls - that's really the bigger interest for me. I play SS gear.

    I think that if there were some magic resistor one could mod their bass with to get a better amp response then we'd probably know about it. I was just going off what I'm reading online and trying to make sense of it.

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