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Pickup Blending Problems with Kent Armstrongs and East Preamp

Discussion in 'Pickups & Electronics [BG]' started by DaveAceofBass, Mar 15, 2009.


  1. DaveAceofBass

    DaveAceofBass Supporting Member

    Feb 20, 2004
    Charlotte, NC
    Hi guys,

    I wanted to get some of your input on this problem, :help: although John East has definitely been trying to help me figure it out and find a remedy.

    The bass is a custom Kinal DK-5 with custom Kent Armstrong soapbars, Graph Tech piezos, and a custom John East preamp. The preamp is a modified 5-knob U-Retro. (The five knob version has a passive blend, unlike the active blend in other East preamps.) I have a serious tone suckout when I blend the magnetic pickups together. We have flipped the wires on the pickups, but they are not wired out of phase with each other (the problem was worse when we tried that). If I can't get the pickups to blend, then I'm going to have to sell them and get something else, :( but I like them and don't really want to do that.

    The pickups are two different styles. The neck pickup is a proprietary design that Kent calls the SS. It's like the one that JP used in JPBasses. It's essentially a humbucker flipped on its side, so it acts like a single coil but is dead quiet. It has a huge fat tone similar to a P bass, but probably bigger sounding. The bridge pickup is a dual coil humbucker, real aggressive sounding, cutting tone, not as warm. With a DC test the neck reads 21K and the bridge 14K. This is odd as the bridge is usually hotter, but Kent said due to the proprietary design of the neck pickup the DC shouldn't affect the output and that this is correct. To my ears, they sound very different, but they have similar output.

    We've tried two other blend pots, with no improvements. Kent's solution was to use a concentric volume pot instead of a blend, and to test it passively first. He said that would fix it. The blending of the pickups loading into each other is the most likely problem, but Kent assured me that the pickups are okay and I don't need to have another one made to match one or the other. Problem is, I don't like the concentric volume idea because there are so many other controls on this bass, it'd just be too much, and harder to set levels. :meh:

    John East was thinking of sending me something to buffer the pickups, but won't that mean I'd lose the passive blending capability? :eyebrow: John might have something up his sleeve though...

    I thought about this earlier tonight...what about a 4-pos. rotary switch? Neck pickup solo/Neck and bridge parallel/neck and bridge series/Bridge pickup solo. Would that work? There's a series/parallel/single switch for the bridge pickup now, would that work with the rotary pot? :confused:
     
  2. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    What kind of blend pot are you using? You know you have to have the ground connection on the correct lug or you lose output in the middle.

    The blend pots are not symmetrical, and since each half is opposite you have to make sure you have them wired the right way.

    An easy way to tell is while the pot is unwired to anything, put the pot in the center detent, and then with a meter read from the center wiper lug to one of the outside lugs and then the other.

    If it's a 250K blend, one side will read about 240K and the other will be about 10K. The ground is connected to the higher resistance side.

    The other deck of the pot is opposite.

    Some blend pots are better than others too.

    You can do the 4 position switch as well. Does matter if the individual pickups have series/parallel switches.

    Buffering the pickups before the blend is the best way to go because they wont load each other.
     
  3. Budha bass

    Budha bass

    Feb 19, 2009
    Paris / France

    Hi,

    This rotary switch is the one fitted in my JPbasses, no need for a blend pot with this one.

    (JP basses : Custom Armstrongs PU with Custom East Pre, so that would work in your case.)
     
  4. Skelf

    Skelf

    Apr 15, 2005
    Moffat D&G Scotland
    Builder AC Guitars.
    I have used the Dingwall switch with Armstrong pickups and an East BTB with out any problems.

    Alan
     

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