Fender Blacktop Precision volume pots

Discussion in 'Pickups & Electronics [BG]' started by mlevendo, Nov 5, 2013.


  1. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    I've had my Fender Blacktop P bass for almost a year now. It's a great bass for cost and I like it a lot. I find it a bit more versitle in tones than my MM StingRay. Like many others with the Blacktop P and J basses, I too dislike the volume pots. The usable volume is in the last 10% and that is being gernous, almost to the point of being unusable. I have read here on TalkBass that others with the Blacktop J have replaced the volume pots with 250k pots instead of the 500k pots to allow vor better volume control. Since the Blacktop P has humbuckers I'm wondering if anyone else out there has swapped the pots out for 250k? What about the tone pot? Leave that at 500k? I have not looked at the pots in my Blacktop P but I am guessing they used the same 500k pots as they used in the Blacktop J basses.
     
  2. wild4oldcars

    wild4oldcars

    Joined:
    Jan 22, 2012
    Messages:
    965
    Location:
    Garner, NC
    250k pots will darken the tone, but will not necessarily allow for better volume control. then you might be getting into tapers, not so much values.
     
  3. Rich McCoy

    Rich McCoy

    Joined:
    Apr 8, 2013
    Messages:
    417
    500k pots are going to give you a hotter output signal and more bite. 250k pots may, and I do mean may, give you more liearity throughout the range of control, but when you turn it down the output level will be a lot less than the 500k pots output level when turned down the same amount.
    I have the Jazz version and there is no way I would replace the pots.
     
  4. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    Exactly. I'm perfectly fine with current tones. Just looking for more control over the volumes for each PU. Right now there is so little room with the current volume pots that it's difficult to mix the two PUs with an accuracy. If I can get more volume control for each PU I will have infinate tonal posibilities. :D
    Thanks for the info.
    Still wonder though if anyone has actually done this with a Blacktop P bass.
     
  5. Register to disable this ad
  6. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    What I am actually wordering is if anyone has replaced pots with something else to give a smoother volume transfer between off and full beside the current low volume at 90% and full volume at 98% :help:
     
  7. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Messages:
    11,382
    Location:
    Brookfield, CT
    It's not 'the pots,' it's the system as a whole and there's really nothing you can do about it except go active (buffer pickups from each other). However, the passive setup works a whole lot better if you don't turn either volume up all the way. Try it. Turn the neck and bridge up to about 75% . Bring up the gain on your amp to compensate. NOW try varying the levels of each pickup-you'll find you have much more flexibility.
     
  8. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    I understand completely. At 75% mine seems to be at such a low signal. Running both volumes at 75% is very low. It seems that any usable signal is closer to the upper 80% with a audible jump to full signal at about 97%. Even if I had usable levels starting at 60% or even 70% I'd be mutch happier. I make it work now but it is difficult to get back to great tone I once found. I tend to run the neck PU a little shy of the all out full volume burst at 97% and then bing up the bridge PU to taste for some growl which is probably around the upper 80% to low 90%. I guess when I think of a volume control I think of an audio receiver or car radio, more gradual. For some reason I just think it should work a little bit better.
     
  9. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Messages:
    11,382
    Location:
    Brookfield, CT
    It won't. It's just the way it is. Compensate with amp gain. That's how every passive Fender player has done it for decades.
     
  10. AlarmClock314

    AlarmClock314

    Joined:
    Mar 26, 2007
    Messages:
    179
    Location:
    Southern WI
    If you have some experience with soldering and are feeling ambitious, this is what I would recommend:
    Replace the pots with
    Neck V: Bourns, 500k linear, solid shaft
    Bridge V: Bourns, 500k linear, solid shaft
    Master T: Bourns, 500k audio, solid shaft

    You could instead use 250k for the volume pots (depending on your personal preference).

    While you're at it, replace the capacitor and input jack. A Switchcraft 1/4" mono jack and a Sprague Orange Drop .047uf capacitor would work just fine (again, preference on the uf value).

    Rewire and now you should have a more usable volume sweep and a nice working bass. It shouldn't cost too much either =)

    Read other TB posts on 250k vs 500k pots, linear vs audio taper, and capacitor values.
     
  11. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    I found this when doing a search on linear vs audio taper:

    "Choosing audio (log) vs. linear depends on what you will be using the pot for. You should always use audio pots for volume control, otherwise you will find that the volume does not change smoothly as you turn the pot up and down. With a linear taper pot, you will find that the volume increases slowly from 0 to about 60 or 70 percent, then increases rapidly from that point on. This is because there isn't a direct relationship between resistance and volume in a passive circuit (which is what a guitar with passive pickups is). Audio taper pots compensate for this, and give you a consistent volume change throughout the sweep.

    A tone control, on the other hand, works best with a linear taper pot. The role of a tone control is to feed part of your signal to a capacitor that bleeds the treble to ground. In order to have a smooth transition from bright tone to mellow tone, the pot has to be linear. You can use an audio taper pot in a tone control, but you won't find the tone roll-off to be as smooth as it could be."

    So correct me if I am wrong here but it sure seems like my Blacktop P Bass has linear pots for the volume on each PU. With very little change in volume for the first 70%+ and a huge jump in that mid to upper 90%.

    By the description above that I had found I should swap them out for audio taper pots (sticking with 500k for the humbuckers). Correct?
     
  12. AlarmClock314

    AlarmClock314

    Joined:
    Mar 26, 2007
    Messages:
    179
    Location:
    Southern WI
    That actually sounds like an audio taper pot.

    I believe the Blacktop J bass has cheap, 500k audio taper pots for all three controls.
    Check this out: http://www.geofex.com/article_folders/potsecrets/potscret.htm
    "If you used an audio taper pot... the output voltage would increase very slowly at first, creeping up to maybe 10% of the final output at 50% of the pot rotation. It would then blast the other 90% in the last half of the rotation - very hard to control. Likewise, if we used a linear pot for volume control, the volume would come up dramatically in the first half of pot rotation, and then do very little change in the last half."

    Pot taper is personal preference. Remember that on positions 0 and 10, the volume levels are identical; only the sweep changes. I prefer to have the volume swell from 0-3 rather than from 7-10. I find that the remaining range from 3-10 to be useful. Also, it may be easier to mix two pickup volume levels together using linear taper pots.

    The value of pots (250k, 500k, ect) may effect its sweep, but I've never tested this before.

    Do what you prefer!
     
  13. Vince Klortho

    Vince Klortho

    Joined:
    Jan 8, 2013
    Messages:
    1,285
    Location:
    Squierville, California
    Have you considered using a volume/balance/tone configuration? That might allow you to have better control over the balance between the pickups.
     
  14. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    Perfect. Exactly the information I have been looking for. I think the info I found on using audio taper for volume was found on a guitar site. I later found that linear pots are better for volume control on basses. I'll either go good quality linears on the volumes and good quality audio taper on the tone. Replace the cap with orange drop matching uf. Replace the jack with a switchcraft mono.
    But now that volume/balance/tone intrigues me. Would the middle position of the balance mean that both PUs are on 100%? Turning left or right would leave one PU at 100% while gradually decreasing the other?
    I do have one issue with 100% (full up) on the PU. They have strong signal (I think a tad more than my MM StingRay with active electronics) and I tend to never run either PU 100%. Staying slightly under 100% (or the last big volume burst as the volume pots work today), they tend to have that more classic warm passive PU tone. If the balance knob runs one PU at 100% and reduces the other, I may not like that. Anyone have some input or experience on a balance knob controlling two PUs. Thanks!
     
  15. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Messages:
    11,382
    Location:
    Brookfield, CT
    I do. It acts more or less the same as what you are experiencing now, like a pickup selector switch. Which is why you don't see balance pots on passive basses. Linear pots will help, but only a little, because this problem isn't due to the audio taper pots- it's about one pickup fighting the other. The only real, effective solution is to use on board buffering or an actual preamp. Just trying to save you some wasted time.
     
  16. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    I guess if a linear pot will reverse what I have going on with the audio pot, I would be better with that. Having finer control of the upper portion of the volume control for each PU is where I would want it. That's pretty much the sweet spot of mixing the two PUs. Right now with the audio pots the sweet spot is in such a small area of adjustment that I will find a real nice mix of the PUs but after changing it I have a real tough time getting back to that same mix again. Having more adjustment room to mix those two in that sweet spot would really make this a killer bass for the price range it is in. Thanks all for sharing your knowledge. Please add more this thread if you think of anything. It will help me and hopefully others. :bassist:
     
  17. Vince Klortho

    Vince Klortho

    Joined:
    Jan 8, 2013
    Messages:
    1,285
    Location:
    Squierville, California
    If you read this and the basses forum you will see that LOTS of people put balance potentiometers in their passive basses, including Blacktops.

    I prefer them because you can adjust the overall volume of the bass without affecting the balance between the pickups.
     
  18. David Jayne

    David Jayne

    Joined:
    Jan 16, 2006
    Messages:
    11,382
    Location:
    Brookfield, CT
    I meant to add 'from the factory......'
     
  19. HCEarwicker

    HCEarwicker

    Joined:
    Aug 30, 2013
    Messages:
    125
    Location:
    London UK
    Hi mlevendo,

    If you haven't already seen it, this thread deals with some of the issues you've raised:

    http://www.talkbass.com/forum/f38/ignoramus-asks-1018530/index2.html

    Yours has been a help to me. Perhaps mine - particularly the stuff on page 2 - may be of some use to you (page 1 includes misinformation compounded by my ignorance, but check the OP).
     
  20. mlevendo

    mlevendo

    Joined:
    Nov 5, 2013
    Messages:
    8
    Yes it was helpfull. Thanks.
     

Share This Page