Help me diagnose low output and distortion on my active bass?

Discussion in 'Pickups & Electronics [BG]' started by Sgroh87, Jan 9, 2014.

  1. Sgroh87


    Dec 4, 2012
    DFW, Texas

    I have a Pedulla 6 string active bass with Bart pickups and preamp that was built in 1993. I've had this thing since this summer, and every once in a while the output on the bass will suddenly drop and the tone will become fuzzy, static-filled, distorted... however you want to describe it. The first time this happened I replaced the battery and the problem went away for a while. However, just a few weeks later, it started happening again intermittently.

    I took it to a local repair tech, and he ruled out that there was a short in the jack draining the battery. He did say that the output jack was pretty worn and not making a very solid connection due to its age, and he wanted to order a jack in and replace it.

    It was going to take too long to get the part in so I took it to another local luthier/repair tech (who is pretty well known; I know a few people on TB have his basses). He pointed out that there were some bad solder spots inside and some of the wires had worn through their insulation. He replaced the output jack and did a complete rewiring and resoldering job on the bass. Problem solved, or so I hoped.

    Last night I accidentally left the bass plugged in overnight. When I got it out this morning to practice a little before work, I noticed that it was doing it again. I replaced the battery with one that had been used, but only for a short time. When I plugged it back in again, it sounded distorted, but after about fifteen seconds it cleared up. I thought everything was good until I sat down to practice tonight and it was distorting again.

    I've emailed Pedulla to see if this is a problem he's had before, and after I hear back from him I'm probably going to talk to the luthier again and see what he can do for me. I was hoping that maybe you guys would have some ideas or suggestions for me.

    Here's a YouTube clip of the actual sound. The video was taken on my phone, but the sound IS an accurate representation of the phenomenon. This is probably the worst that it has ever sounded. It's not this bad right now, but if I don't get this sorted out then it may end up this bad again. Please don't judge my playing. ;)
  2. Leaving it plugged in will drain the battery. The negative lead from the battery is normally switched by contact with the sleeve of the plug. Get a completely new battery out of the package and then try it. If there are any issues with a new battery in it, then call the guy.

    If it sounds like this with a brand new battery in it you've likely killed a component in the preamp. I can't tell you what for sure.
  3. Sgroh87


    Dec 4, 2012
    DFW, Texas
  4. Hi.

    Is it a Neutrik jack?

    Most of the people on the barrel jack related threads swear that whatever will do, but IME the only choice is Neutrik.
    And even that will fail relatively quickly compared with a CTS open one for example.
    A marred plug tip is a sure way to destroy a barrel jack in a few weeks.

    One possibility is also a corroded plug.
    The pre-amp draws so little juice that even the tiniest oxide layer will cut the circuit on the poor mans way of using the R&S as the voltage ground path for the pre-amp.

    (Un?)fortunately there's no barrel jacks with switching contacts that I know of so there's no direct replacement, but my suggestion is always to replace the jack anyway. Even though it does require routing the body.

  5. JustForSport


    Nov 17, 2011
    Try a new Duracel first.
  6. 96tbird

    96tbird PLEASE STAND BY Supporting Member

    Yes, ditch that no name battery and spring for a good one.
  7. fhm555

    fhm555 So FOS my eyes are brown Supporting Member

    Feb 16, 2011
    I'll third the "get a real battery" idea.

    I've bought no name batteries when I had no choice and had about half of them be inadequate out of the package to drive the pre in my US J Plus.

    Go to a place like your friendly neighborhood AllMart where battery turnover will be high and you can be reasonably assured the cells you are getting are factory fresh, and buy a couple of copper tops before calling in an expert.
  8. Sgroh87


    Dec 4, 2012
    DFW, Texas
    Well, I just went to the store and got some new Duracell 9v batteries and installed one of them. Static is still there. The strange thing is that the static is only present when the strings are vibrating. When i mute the strings, it's dead silent.
  9. pfox14


    Dec 22, 2013
    Have you eliminated all other possible causes? Try a new cord. Try plugging into another amp.
  10. Sgroh87


    Dec 4, 2012
    DFW, Texas
    Yeah, I have. I have two chords and it acts like that on both of them. I've run another instrument through my amp and there's no problem with it. My repair guy (Pavel of ) is pretty sure from my description that it's the preamp going out.
  11. JustForSport


    Nov 17, 2011
    Could be a 'cold' solder connection that hasn't completely come apart- not full signal transfer: same as a weak battery.
  12. MethodsofDance


    Nov 19, 2013
    This sounds like exactly the same problem I was having with my Ibanez SR300F. I took it to get looked over and the guy said all the wiring looked ok, I couldn't explain the problem. Different cables, different batteries, I tried a whole bunch of things. I eventually decided it was down to the little Behringer mixer I play through being a bit old and not in the best shape. The (passive) bass I own now hasn't given me the problem though. I was concerned it was something to do with the pickup itself, at which point I decided to get rid of it and make sure my next bass was passive.
  13. RobbieK


    Jun 14, 2003
    I get to diagnose these sort of things quite often. I'm afraid that with a circuit like this with 3 or 4 bartolini boxes, and after all the rewirings etc, it's time to go one by one. What I mean is to desolder the pickups and test them individually. Then test the twin buffer, first with a signal generator (remove it's outputs from the circuit too), and then with the pickups back. Then it's on to the pre. etc. etc. You'll have to find a good, patient tech...
  14. Sgroh87


    Dec 4, 2012
    DFW, Texas
    I talked it over with my repair guy and he said that he'll install a new preamp for $30 labor since he did a full rewiring for me already. $160 for the preamp and $30 or so for the knobs, so about $230 all told. Not a terrible deal.
  15. RobbieK


    Jun 14, 2003
    Yeah, I'm afraid that's kinda how it rolls mate. The labour to diagnose a pre like that will probably be as much as a new pre. Tech's gotta family to feed. Besides, even if he/she sussed which box was at fault, tracking a replacement from bart might be hard, and, yeah almost as much as a whole new (modern, single box) preamp. There's a good chance your bass will sound a bit different though...