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Balance pot question?

Discussion in 'Pickups & Electronics [BG]' started by tubehead2, Feb 13, 2013.


  1. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    I just install new set of Delano pickups in my warwick state 2 in passive and Vol-Bal-Tone configuration.

    I like the tone of it but output of the bass noticeably decrease.
    With Delano pickup the output is very low. I used to turn both gain and volume knob in my amp at 10-10.30 but right now I have them at 12.00 to get same sound level.

    After I play around for a while, I just notice that the output increase a bit when I turn the balance all the way up or down using only neck or bridge pickup.

    This quite strange to me, in Vol-Vol-tone common Jazz bass configuration which I get used to, the maximum output can be get from turning both volume all the way up.

    Is this common thing for balance pot?
     
  2. Cadfael

    Cadfael

    Joined:
    Jan 4, 2013
    Location:
    Germany, EU
    1.) It is not normal that the output generally noticeably decrease ...
    Did you install a 500k balance pot?
    HOT and GND are on the outer connectors, wired diagonal form upper to lower pot? PU-HOT is in the middle?

    2.) It is normal that the parallel volume (middle position) is a bit lower than full-left or full-right.
    The impedance of the PUs has no direct, but indirect influence on the output. In the middle position you have about half the impedance compared to full-left/-right.
    (1/Itotal = 1/I1 + 1/I2)

    Can a HOT connection have contact to a grounded part or grounded cavity? Especially a black shielding might cuase a restistance to a HOT part touching which is big enough to still hear a tone but small enough to lower the output ...
    Put a piece of paper (as isolator) under the balance pot. Better? If yet, use something more lasting to isolate the pot connectors (like plastic tape).
     
  3. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    Thank a lot Cadfael

    1. I use 250K balance pot. And everything is correct.
    2. I see. So I do not have to worry about that.

    I already check hot and ground, not found anything wrong.
    I will recheck again tomorrow.

    May be the pickup itself has not much output.

    Do you think Bartolini TC3 can help?
    Is 12db more gain is too much?

    http://www.bestbassgear.com/bartolini-preamps-tc3.htm
     
  4. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    As Cadfael mentioned, what a blend pot does at the center detent is place both pickups in parallel. This means that the input impedance loading either coil is lowest at the position, since favoring either pickup increases the output impedance of one pickup, decreasing the resistive load on the other. The volume drop at the center position is normal, and there isn't much you can do about it, with the nature of passive wiring. You can try active buffered blends, if you want, though.

    I find it interesting, however, that you don't have insertion loss issues with a VVT setup. VVT is electrically identical to VBT, except that VBT has one extra volume pot. If you roll one volume down slightly, the other pickup should be louder, just like in a VBT setup.
     
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  6. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    This formula is correct, but just a side note, "I" is the symbol for current, and parallel current sources don't work that way. Impedance is "Z."
     
  7. Cadfael

    Cadfael

    Joined:
    Jan 4, 2013
    Location:
    Germany, EU
    Got me once again! :D

    At school during becoming a skilled metal worker (President Obama praised our German dual-system today?!) I had an "A" in "controlling & regulate" (building and background of hydraulic and pneumatic systems).
    At grammer school I was always a "D" student in physics ...

    The 250k pot may be a little bit too low - but I had a Warwick Rockbass Streamer which had a 25k pot - and worked.

    What you should do:
    Connect one of the Delano PUs (or both PUs in parallel) directly to the jack! What does the amp say? Is it MUCH better? (a bit better might be normal).

    Delanos normally have a "normal" output! I have JC4 AL/M2 in my "Elwood" Jazz Bass (copy). There is no difference to my other Jazz basses ...

    If the output is much higher, connecting the PUs directly, you made a mistake somewhere - or one of the pots doesn't work correct ...

    Connecting the PUs directly gives you the first hint where the problem is. The PUs themselfes or the pots / cap / wiring?

    You have to find a "systematic error research" then. A multimeter would surely help ...
     
  8. bumperbass

    bumperbass

    Joined:
    Jun 19, 2012
    250K sounds kind of low for a balance pot. Mine's a 1 meg. That's 500K loading on each pickup in the center position. Another volume control after that would loading it down.
     
  9. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    500k on both pickups. They run parallel to each other at the center detent.
     
  10. bumperbass

    bumperbass

    Joined:
    Jun 19, 2012
    Yeah. ^^What he said that I said (meant). Thanks, L6man!
     
  11. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    Thank you all.

    I am using the Jazz bass blend form seymour website, it specific 250k blend control pot
    and there is only 250K blend pot in best bass gear.


    So where can I find 500K or 1 meg blend control pot?
     
  12. walterw

    walterw Supportive Fender Gold Supporting Member

    Joined:
    Feb 20, 2009
    is this 250k balance pot an "M/N" type or an "A/C" type? if it's not M/N, then the middle setting is actually both pickups turned down a bit.

    M/N pots leave both pickups at 100% in the center, only bringing one or the other down when you turn it.

    use a 250k M/N, then leave the ground connections off the other lugs, and you'll get no loss from it.
     
  13. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    I use 250k blend pot from bestbassgear, do not know if it "M/N" type or an "A/C" type.

    However, I did measure it with digital meter when the pot set in middle position it reads 265k from outer lug to outer lug and 225K, 40K from middle lug to outer lugs.

    So i think it is A/C type.
    Where can I buy M/N type?
    What value should be use? 250K 500K or ???
     
  14. walterw

    walterw Supportive Fender Gold Supporting Member

    Joined:
    Feb 20, 2009
    aha!

    it's not the right kind.

    the bourns M/N you get at allparts (when centered) reads more like 250kΩ from middle to one side and 10Ω from middle to the other side!

    that will keep the pickups at full output in the middle, especially if you do the "ungrounded" trick, where you bring the two pickups in to the center lugs, jump the two output lugs and send that off to the volume pot, and leave the rest of the lugs alone.
     
  15. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    Thank so much Walterw.

    Right now a problem is solved.

    After recheck the wiring again, nothing wrong. And when Blend pot is turned fully on or off the output is close too normal. So at this point I conclude that I am using wrong type of blend pot.

    The M/N type blend pot should solve the low output when the pot set in the middle.

    The problem left is what value of blend pot and volume should be use ?

    And I ordered bartolini TC3 from BBG last night should where should I place it?

    Blend pot > TC3 > Volume > tone > output jack or
    Blend pot > Volume > tone > TC3 > output jack

    any idea?
     
  16. walterw

    walterw Supportive Fender Gold Supporting Member

    Joined:
    Feb 20, 2009
    i'd say normal is pickups-->blend pot-->250k or 500k linear volume pot-->preamp-->output

    if you wanted no volume pot loading, you could put the preamp after the blend and use a 25k or 50k volume pot after the preamp.

    having the blend and volume stay up front and passive gives you the option to switch the preamp out for passive operation.
     
  17. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    Thank a lot. I think I have to try every way and use my ears as a judge ^^.
     
  18. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    I just try replacing 250K Vol with 500K.
    I prefer the tone of 500K, more natural tone, not too tight bass and slightly more high.

    And the output between center and 100% up/down blend pot are no more problem.
    I can not hear any difference in output.

    The bass output still a little too low for me but I think Bartolini TC3 will
    ease the problem smoothly. ^^

    Thank again, everyone.
     
  19. SGD Lutherie

    SGD Lutherie Banned

    Joined:
    Aug 21, 2008
    Location:
    Bloomfield, NJ
    Disclosures:
    Owner, SGD Music Products
    Are you sure? How do you know?

    There is a right and wrong way to wire the blend pot. If you are it up the wrong way then you will love volume n the middle.

    The way to tell if you have it wired right is to put the blend in the center detent, then measure from the center wiper terminal to the two output ones. One side should read almost the full value of the pot, and the other side should be close to zero ohms.

    The higher side goes to ground, and the low side goes to hot.

    Here's an example with a 500k pot.

    [​IMG]

    Different blend pots are set up different ways, so you have to check them. Also, M/N taper works better than A/B taper. M/N gives full volume at the center.
     
  20. tubehead2

    tubehead2

    Joined:
    Jan 26, 2013
    I have experienced the problem before with my other bass.
    Connected signal and ground to wrong side cause the output dramatically weak. So that is the first thing I check out after notice the output is weak. Thanks BBG for the very useful article.

    http://www.bestbassgear.com/ebass/gear/electronics/pickup/nordstrand-wiring-diagrams.html

    And about the A/B and M/N pot types, I think of it this way. With A/B type that I have on hand, the output in the center lower than the M/N type . But the output in the 100% up or down is the same (I assume please correct me if I am wrong)

    With M/N types, the max output is in the center, the A/B type works opposite way. I normally prefer the single neck or bridge pu a little louder for solo, and use both pu for walking.
    I already ordered Bartolini TC3 which will boost over all output of the bass around 12db, so I hope the low output problem will be solved and may be too high output will be my next problem :p.

    I have no idea how +12db output will do to my bass.

    Do u have any idea?

    I will try the M/N type soon too. But I live in Thailand, the shipping fee costs me many time more than the price of the pot so I have to think carefully which items I should have too.
     

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