Tobias/Bartolini inquiry

Discussion in 'Pickups & Electronics [BG]' started by abarson, Oct 18, 2012.


  1. abarson

    abarson

    Joined:
    Nov 6, 2003
    Location:
    Santa Cruz
    I've got one of the older Tobias Growlers, with the single volume, balance, two stacked bass/treble controls and two toggle switches. My understanding is that the pickup and EQ are from Bartolini.
    My problem is that this bass no longer has any power to it, no "oomph". The controls all operate as they are supposed to, but the whole thing just lacks the powerful output it had when I bought it. I've replaced the batteries and changed strings (obvious and simple), but it didn't do much. Anything else I should be checking?
    Does anyone have a wiring diagram for this rats nest? It might give me a clue what to check, even though the controls are working.
    If that fails, does anyone have a good replacement recommendation?
    :help:
  2. sotua

    sotua

    Joined:
    Sep 20, 2004
    Location:
    Chile
    Have you moved the pickup height?

    You could also check if the preamp has internal trim pots to boost the gain.
  3. Doug Parent

    Doug Parent Gold Supporting Member

    Joined:
    May 31, 2004
    Location:
    San Diego, Ca.
    If the controls are working don't mess with the rats nest unless you want to learn how to rewire a preamp vs. playing your bass. As far as I know, the Bart preamp can have a faulty component, but that would be inside the epoxied "brick" and the only problem I had with a Bart pre was battery consumption went way up as a result. If you think it's the the electronics, and are up for an adventure, you can swap the preamp. Suggest you
    research this before you start tearing that apart. Maybe take a picture of the rats nest and see if someone can identify the pre. Is it a domestic made bass or import?
  4. abarson

    abarson

    Joined:
    Nov 6, 2003
    Location:
    Santa Cruz
    I can confirm that I haven't changed the pickup height. Any recommendation of what the appropriate gap between the pickup top and the bottom of the strings should be?

    It does have trim pots, but if I need to boost the gain, something has changed over time. Is that typical?

    This is the first generation Growler, made in Tennessee. Someone on a different forum thinks that it is a Bartolini DNTBT-18, if that helps.
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  6. abarson

    abarson

    Joined:
    Nov 6, 2003
    Location:
    Santa Cruz
    Well, it turns out that the 9 volt batteries were both below 7 volts, but they're only a couple of months old. I wouldn't expect them to drain so quickly. I've been careful not to leave the cable in the jack when I'm not playing. I poked around looking for anything that may be shorted to ground and came up empty-handed.

    Does anyone know what each of the two trim pots per preamp does?

    One more question: is it typical to have multiple ground points soldered to the shielding? I thought the common practice is to bring all those wires to one spot.

    Attached Files:

  7. Rano Bass

    Rano Bass

    Joined:
    Sep 9, 2006
    Location:
    Tijuana Mex.
    IIRC two of those trim pots are for output gain and the other two control something about the midrange boost/cut controls.
    Those preamps are really complicated to look at.
  8. abarson

    abarson

    Joined:
    Nov 6, 2003
    Location:
    Santa Cruz
    I'm following up on the suggestion to check pickup height that sotua mentioned. It's a MM humbucker shape with three screws to adjust height. I raised the screws, but the pickup isn't rising. Are there supposed to be springs that push the pickup up on its screw, or just the foam padding in the bottom?
  9. Jaco Taco

    Jaco Taco

    Joined:
    Jul 30, 2012
    Oh, active pickups, how silly they are! :smug::bag:
  10. mmbongo

    mmbongo I like turtles. Supporting Member

    Joined:
    Aug 5, 2009
    Location:
    Upstate, South Carolina
    He doesn't have active pickups. :eek:
  11. Jaco Taco

    Jaco Taco

    Joined:
    Jul 30, 2012
    Batteries..... :eyebrow:
  12. bongomania

    bongomania Gold Supporting Member

    Joined:
    Oct 17, 2005
    Location:
    PDX, OR
    Disclosures:
    owner, OVNIFX and OVNILabs
    Those are for the preamp and EQ, not for the pickups.
  13. 73jbass

    73jbass Gold Supporting Member

    Joined:
    Apr 17, 2004
    Location:
    Ellenwood,Ga.
    What he means is the pickups are passive with active electronics.
  14. pb9717

    pb9717 Supporting Member

    Joined:
    Aug 18, 2006
    The Growler has 3 individual preamps (2) individual varible frequesncy Mid pre's ( the ones at 12 and 2 oclock) and the big mamajama in the center of the cavity where the pickup connects to, that does bass & Treble. The cavity is fully shielded and grounds at multiple points. The electronics in 1st gen growlers are very complicated, well designed, and VALUABLE, since they can no longer be replaced. The pickup is also actually FOUR individual pickups in one cover. Very difficult to construct and also no longer available to replace. My guess is you got a couple or one bad battery. Bring up the pickup to a good height for correct volume (not too loud) and try it out again. I highly discourage replacing the preamp/pickup The electronics are the heart and soul of the Growler, and coupled with it being well set up, can make for a really great bass. Killer , SNappy and cutting sound.

    good luck.

    heres a pic of mine.

    [​IMG]
  15. SGD Lutherie

    SGD Lutherie Supporting Member

    Joined:
    Aug 21, 2008
    Location:
    Bloomfield, NJ
    Disclosures:
    Owner, SGD Music Products
    Yes it is. There's no reason to solder grounds to one spot. It's all ground.
  16. moonshinegtrs

    moonshinegtrs

    Joined:
    Jan 28, 2009
    Location:
    White Bluff,Tn.
    Disclosures:
    Owner: Moonshine Custom Guitars
    The Growler (the early models with this particular pre-amp) are really great sounding instruments and a lot of that is due to the Bart pre-amp (I believe that this was Bill's most complicated unit & one of the reasons that it is no longer in production... IMHO) & the really cool four coil (two humbucking pickups in one casing) pickup.

    The newer models don't hold a candle to the early Growlers. Totally different animals.

    Moonshine :bassist:
  17. abarson

    abarson

    Joined:
    Nov 6, 2003
    Location:
    Santa Cruz
    As stated:
    1. Batteries replaced - negligible difference.
    2. Ammeter used to make sure that
    a) no current is being drawn when the cord is not plugged into the output jack, and
    b) no more than 4 mA are drawn when it is plugged into the jack.

    How do I further troubleshoot whether the problem is with the pickup (low output from the pickup into the preamp) or that the preamp is kaput, even after I've checked the current draw?

    Neither Bartolini or Gibson/Tobias are any help. I'm on the verge of giving up on this bass, but right now it's the only one I own.
  18. ctmullins

    ctmullins Registered 8er Supporting Member

    Joined:
    Apr 18, 2008
    Location:
    MS Gulf Coast
    Did you measure the battery voltage before installing them? It's possible the batteries could be weak straight from the manufacturer. Not common, but possible, and easy to verify.

    Failing that, I would temporarily wire the pickup straight to the jack, or to some jumper wires straight to a cable. Of course, this may not be feasible or agreeable due to the wiring complexity; I don't know. It all depends on how much you're willing to go to troubleshoot. But that's the only way I know of to determine if the problem is with the pickup or the preamp.

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