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Electronics question, but no responses in other forum

Discussion in 'Luthier's Corner' started by Basschair, Aug 4, 2005.

  1. Basschair

    Basschair .............. Supporting Member

    Feb 5, 2004
    Stockton, Ca
    Hey guys,

    I posted this in the electronics forum, but didn't get any bites. Hope no one minds if I repost here as well...

    Aguilar obp-3 with vol, vol, treb/bass stack, sweepable mid, and tone pots.
    Nordstrand NJ5st pair (sick...absolutely sick. Mr. Nordstrand does a great job)

    Here's the deal: there is this subtle "muah" sound going on that shouldn't be. Normally I'd think "muah" is great, right? Well, this happens when open strings are plucked, and sounds like this: the note is produced clean, then gets a bit lounder and loses focus, almost like a single instance of and out-of-phase harmonic beating.

    After boosting/cutting settings, I've narrowed it down to the tone pot. The only way to completely get rid of it (at least to my ears) is to turn the tone pot all the way down. My questions are these:

    1. anyone else ever had a tone pot do this?

    2. could it be something else and the tone pot simple helps it be heard?

    3. if it is the tone pot, could it be a grounding issue, or is it probably a bad pot?

    4. does it make absolutely no sense, and I should go back to trying to isolate the sound?

    If you'd rather respond in the other forum, here's the link:

    Thanks for any help!
  2. Rodent

    Rodent A Killer Pickup Line™ Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Honey Badger Pickups & Regenerate Guitar Works
    question for you: are you using DR stainless strings by chance?

    I had a similar thing happen on a bass I made. Changed strings to a non-DR brand and presto! it was gone. It's a real bummer, too, cuz I just love DR's. :crying:

  3. Basschair

    Basschair .............. Supporting Member

    Feb 5, 2004
    Stockton, Ca
    Nope. I'm using Rotosound 88 tapewounds. A pretty good string, and my first time with them. I've got DR's on my Warwick which isn't making any sound similar to this one I'm dealing with. Thanks for the comment though!
  4. flange


    Feb 22, 2005
    Cochrane Alberta
    Since you've already isolated this to the tone pot this might not be relevant. If the sound is somewhat like a wah I would suspect something in the mid sweep control or battery.That is to say that if the voltage is varying maybe thats creating the noise. Just a suggestion.
  5. Basschair

    Basschair .............. Supporting Member

    Feb 5, 2004
    Stockton, Ca
    Well, it sounds like it's the tone pot, but I'll give the mids a try in a few minutes. What would cause a fluctuation in the voltage?
  6. fivehawks


    Aug 4, 2005
    Greetings my friend,
    I'm an apprentice working for John Carruthers for a good long while, a newly appointed bass fanatic due to the great basses we build :) I made more money in the last month playing bass than 20 years of guitar playing. Thanks, L.A. Here are some thoughts with regards to the "muah" problem, and I'm 99 44/100s sure it is not electronics:
    1) Strings, strings, strings. If you change gauges of strings, you'll get this "muah" sound from the string vibrating past the nut. You will have to reslot your nut if you change gauges and it should give you a solid sound. The main clue is that it happens on OPEN string plucking.
    2) Bridge Saddles. If the action is not set up correctly, the string may not come off the saddle correctly and generate this sound. Same idea as the nut problem - the string is vibrating past the saddle.
    3) Strings again: certain string gauges with long scale basses will "muah" around because they do not achieve enough tension. Try a heavier gauge and remember to reslot the nut.

    Your electronics will not produce a changing frequency automatically unless you have static in your pot, and then most likely it will be an abrupt change in tone instead of a muah, accompanied by a nice crackle.

    I hope this helps! If you have any qestion, email me - I'll be happy to help.
  7. Basschair

    Basschair .............. Supporting Member

    Feb 5, 2004
    Stockton, Ca
    Thanks for the suggestion Rick. I'll break out the files and check the nut. I'm using pretty heavy strings as is, though they still have a fairly loose tension. At any rate, I'll try some things tonight...
  8. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    I'd agree that the problem is mechanical, not electronics. Turning down the treble simply removes the offending sound.

    I'd agree also that it is nut-related, but most likely not due to resonance of the string between the nut and tuner. More likely it's because the string is moving in the nut slot. After plucking the string, the vibration goes through shifts in parallel-to-fingerboard and perpendicular-to-fingerboard vibrational modes, and this would be why the effect does not happen until shortly after the note is plucked.

    Most likely the slot should be filled and properly re-slotted.
  9. Suburban


    Jan 15, 2001
    lower mid Sweden
    Definitely a mech problem. Whether it is nut or bridge, is to me an open question. The same effect can occur if the witness point at the bridge is "impure".
    You can also have this kind of effect in a spring, i.e. if there is a spring somewhere in your instrument, you need to check that, too.

    How to find the problem: use a hose! Put one end to your ear, pluck the string and move the other end of the hose over the bass (not in contact!). You will now be able to tell where the sound is loudest, i.e. where it comes from. Investigate that part, and remedy the problem.

    Simple, isn't it? :D