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John east j-tone issue

Discussion in 'Pickups & Electronics [BG]' started by baTassi, Nov 18, 2018.

  1. Hi everyone.
    I'mhaving an issue with my j-tone. I installed it 2 weeks ago with a brand new battery and it was perfect, everything worked as expected and it made the bass sound great. I couldn't been happier, it made a bass I didn't like the pickups sound amazing.
    I used it on a rehearsal for 2-3 hours with no issues.
    Next week after that, I connected the bass and after 10-20 seconds a weird noise started to raise very fast. It wasn't hum, it sounded like an electronic noise and started to escalate very quickly. I tried to get the volume down but somehow, it was worst. So, I muted the amp and unplugged the bass. I tried again with the same result.
    Then I tried another bass with the same setup (cable and amp no pedals in the chain) and no issues what so ever. Since I couldn't take the bass home at the time I couldn't test any further.
    Today I opened it and checked the connections, made sure the ground was ok and moved the the dials a bit. Also checked the caps where ok. No visible issues whatsoever.
    I tried the bass again and it works perfectly on passive mode, but on active move, no sound, nothing. The noise is gone but also the bass sound. Any ideas? What else I can check or try?

    I'm taking the bass home so i can do some other tests like trying with another battery.
    I just sent to John through him web to see if they can help
  2. I got an asnwer from John a few hours after I posted this. I was able to try another baterry until today, but it seems that was the whole issue (I'll do some more testing this week).

    This is the explanaition John gave me:

    If the battery is low, it shouldn't be less that 6V when under load (ie when the preamp is on), sometimes the chips can go unstable and create very nasty noises.
    This only happens when the voltage is well below the 6V, which is the spec for the chips. Often they will work at much lower voltages, but some do go unstable, due to a battery in a poor state.
    I have had this reported a few times in the past and even had preamps here which have exhibited such behaviour but not managed to recreate the issue. But in the end, I have managed to fake what is going on with a bench test. It's down to a very weak battery. It powers up the preamp, then being very weak, starts to fail, unable to keep the preamp going. The preamp chips shut themselves off. Then the battery recovers a little and the voltage goes up. Then it's enough the fire-up the preamp again, but can't sustain it, so the chips shut off again.
    This occurs in fast succession, fire up, die, fire up die, this is the nasty noise. So the only way is to replace the battery as soon as below 6V when powering the preamp.
    Many chips shut down without any noise with a low battery, but often these, higher spec chips, don't.

    I'm really happy with the product, I was before and now even more becuase I see that the guy behind it is there to back it up, to take care of the customer.

    If moderators want to clsoe this trhead or deleted it's fine for me, I just thought of leaving it here in case someone have a similar problem in the future

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