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Weird 'rattle' when I play an A

Discussion in 'Setup & Repair [DB]' started by Warpeg, Oct 10, 2018.

  1. Warpeg


    Jun 20, 2005
    So, I discovered a few weeks ago that my plywood DB has an internal rattling sound whenever I play an A (of any octave). It's not a loud rattle, but it's loud enough that I feel the need to troubleshoot it. Here's what I have checked and eliminated so far:
    • The rattle is only apparent when I play an A with moderate or higher pizz force. Quietly-played A's do not have the rattle. So, something inside the bass seems to have a resonant frequency of 110, 220, 440, 880Hz, etc.
    • It's unknown if I get the rattle arco, as the sustaining of the notes would cover up the rattling sound anyway.
    • End pin assembly: Everything appears tight and firm, at least on the outside
    • Bridge and bridge piezo pickup: Nothing appears to move or shift
    • Tailpiece and string ends: Everything appears to be solid
    • Neck, figerboard, tuning machines: The sound seems to be coming from the body of the bass.
    • Soundpost: A visual inspection shows no issues, but I'm really not an expert there.
    Does anyone have any ideas or suggestions for additional troubleshooting? Thanks in advance.
  2. jackn1202


    Feb 14, 2018
    Austin, TX
    How long have you had the bass? It could just be a wolf tone. However, my cello had a similar problem awhile back, but it turned out to be a loose string end in the headstock that was affected by certain frequencies, it would buzz. I found the offender, tucked it in behind a peg, and never had the problem again. That's a lie, it popped out one time so I fixed it again. But yeah, I'd check your string ends in the headstock.
  3. Could it be the A string itself? I've seen old wound strings rattle as the windings loosen up.

    Do you have a pickup installed? I've seen pickup wires rattling against the tailpiece in the past.

    Are the loose string-ends in the pegbox rattling? I've also seen this in the past.
  4. Warpeg


    Jun 20, 2005
    Thanks. I've had the bass for about two months. For all I know, the rattle was there when I got the bass, but I didn't catch it until recently. I'll check the head, but rattle really sounds like it's coming from the body area. It's hard for me to play an A and also move my ear closely around the bass to try to pinpoint the rattle, though.
  5. getrhythm


    Nov 2, 2015
    New Jersey
    My open G would rattle. I have to constantly tighten the endpin set screw.
    jackn1202 likes this.
  6. Warpeg


    Jun 20, 2005

    I suppose it could be the A string. I don't have any extra A strings. Is there a way to troubleshoot it without using a new string?

    There is a dual sensor pickup installed. However, I have everything installed nice and tight, and I do recall having the rattle before I installed the pickup recently.

    Everything looks very tidy in the pegbox to my (inexperienced) eyes. What should I be looking for?
  7. jackn1202


    Feb 14, 2018
    Austin, TX
    That's fair. It was awhile back but I think what happened to my cello sounded like it was coming from the body too, just 'cuz that's the most resonant area (duh). The sound got magnified by the body. Also, it doesn't take much of a string end to make a noise.

    But I could be very wrong.
  8. Warpeg


    Jun 20, 2005
    That was the first place I looked, too. The set screw is nice and tight, as well as everything else that I can see on the endpin assembly. Is it possible that there is a part of the assembly inside the bass that is vibrating?
  9. Try to replicate the problem by playing a closed A on the E string. If you get nothing, likely either the string is bad, mounted incorrectly, or there’s a problem with the string path.

    If the rattle is frequency-specific, check for an open seam by rapping with a knuckle around the perimeter of the top and back plates. If any part goes bang-bang instead of thunk-thunk, that’s it.
  10. Warpeg


    Jun 20, 2005
    That's a great point. I do get the rattle on all A's played on all strings. I guess that means it wouldn't be just an A-string issue?

    Thanks for the suggestion on the open seem troubleshooting. I'll try that tonight. If there is an open seem, should I assume that a professional would need to glue it, or is this something that I may be able to address myself?
  11. wathaet


    May 27, 2007
    unless it is an A wolf in which case playing A on the E string will eliminate the wolf if the A string is free to vibrate
  12. It’s a simple and cheap repair. Not a big deal.
  13. Carl Hillman

    Carl Hillman

    Jan 1, 2010
    Play it after you take the endpin and the set screw out to eliminate the possibility that's were the rattle is coming from.

    If it's still making noise, and it's not an open seam, get a mirror and a light and look inside at the bass bar.
    getrhythm and wathaet like this.
  14. Warpeg


    Jun 20, 2005
    I just played it at home on my lunch break. Interestingly, I only get the rattle when I extend the endpin to my playing position. If the endpin is shortened any, or even completely pushed back into the body, the rattle goes away. Is it possible that there is some part of the endpin assembly inside the bass that is causing the rattle?
  15. Absolutely. If the pin is too long it vibrates like a tuning fork inside the box. It also adds excess weight.
  16. Warpeg


    Jun 20, 2005
    Thanks. Is it common to cut the pin, or should I experiment with something like wrapping a small amount of tape around the top of the post to act as a bit of a cushion?
  17. Some times, just turning the endpin can change something (if it is slightly curved fx). 180/90 degrees.
  18. Try isolating the shaft with a layer of packing tape first.
  19. Just to be sure that either end of the bass bar has not come unstuck tap the bass front at each end of the bar and see if that makes a rattling sound. If the rattle turns out to be the end pin then is this a solid rod or a tube-style? The former will often rattle if the hole through which it passes is too big or not round. It should not be a big cost to replace the end pin assembly with another solid rod but a cork lined hole, or a tubular style rod that is lighter.
  20. mooseonbass

    mooseonbass Supporting Member

    Jun 24, 2011
    I have the same problem intermittantly. (Mine is also with th A) It turns out that there is a small, previously repaired rib crack that is responsible. When it happens, I put my finger on the crack and it stops. I finally took it to my luthier and, of course, there was no rattle. He said to bring it back next time that it happens and he’ll fix it up. So far, no more rattle though. He may just be magic!

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