Disconcerting sound coming from amp... sounds like broken glass rattling or a bowl of marbles

Discussion in 'Amps and Cabs [BG]' started by Dave Campbell, Dec 30, 2014.

  1. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    Recently picked up an Ashdown EVO 300, LOVE the tone, in the short amount of time I've had it it's solely been plugged into an Avatar 112 8ohm cab, used twice during rehearsals. The first time around no issues whatsoever but at practice the other day after about a half hour of steady playing at 50% volume, a weird sound became audible when plucking the strings on my P Bass... everyone in the room assumed the speaker was toast in the cab (it's about 10 years old, been used a lot)... kind of sounded like a bowl of marbles or broken glass vibrating. Sorry to sound like a noob, I just can't find a better way to describe it...

    I toughed it out for the duration of the practice, and then yesterday brought my Eden 410 cab as a potential backup, but started the day using the Avatar again, this time with my loyal and faithful Thunderfunk TFB420 amp, to troubleshoot if it was the speaker that was messed up. No weirdness at all, so I'm gathering it's the Ashdown head I just acquired.

    If it really is the amp, what on earth could be going on inside?
  2. bad pre-amp tube??
    Jim Carr and B-string like this.
  3. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    Pretty sure it's strictly solid state throughout.
  4. Sorry, I'm just going by what the ashdown website said ( "blend of solid state and dual triode tube preamps stages" ) and a search here that brought up a tube rolling thread for them ("What is correct pre-amp tube for Ashdown EVO 300 ??"). If yours is a different model, without the tube pre (looks like it's had several model revisions evoii and iii) I apologize, please disregard.
    Last edited: Dec 30, 2014
  5. BassmanPaul

    BassmanPaul Inactive

    It does sound very much like a microphonic tube to me too. Disconnect your bass, turn the amp up and bang your fist on the top. If you hear a similar noise then a tube could be it. If no tube I'm stumped without getting my hands on the amp.
    Last edited: Dec 30, 2014
    Jim Carr and B-string like this.
  6. I agree check for a preamp tube in there, I have also come across small signal caps that became notably microphonic as well. You will need an amp tech in that case.
  7. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    Hey yes that is it, although I believe it's the previous generation, looks exactly the same (but is 300W).
    A preamp tube... Wow, had no idea!
  8. mh72nc


    Sep 2, 2009
    terre haute, in
    My Genz Benz Shuttle 9.0 does that every once in a while. I found that resting my head on my avatar cab (surely that's a coincidence) slowly loosened the screws that held the case together, causing things to vibrate. So every month or two i make sure the screws are tightened down, and I no longer put my head on top of my cabinet. Seems to have solved the issue for the most part. It needs a good slap on the top every once in a while still, though.
  9. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    @Dave Campbell — I agree it is tube microphonics that you are hearing. Try setting the rig up with the amp head NOT on top of the speaker. There can be a "feedback loop" between the tube and the cabinet vibrations that worsens the problem. Separating head and cab can help a bit. You need a new tube.
  10. RED J

    RED J Lol

    Jan 23, 2000
    Microphonic tuuuuuuuuuuuuube.
  11. Dave Campbell

    Dave Campbell

    Jul 13, 2006
    What's the most amount of money I should pay for a tube?
    For fun I looked on Ebay last night, wow, quite a range in pricing.

    I also found that earlier
    thread on the Ashdown and tube swapping, for those guys who really know their stuff it sounds like tube swapping can get quite interesting.
  12. For a single tube hybrid amp more than $40.00 for a preamp tube is more for "fun" than useful. IMO, IME ;)
  13. Dave Campbell

    Dave Campbell

    Jul 13, 2006
  14. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Get a new tube. Don't waste money with NOS. Cost: around $15.
  15. dincz


    Sep 25, 2010
    Czech Republic
    Doesn't that interfere with your playing, and do you get strange looks from the audience?
    mh72nc and BassmanPaul like this.
  16. devnulljp

    devnulljp Supporting Member

    Oct 13, 2009
    BC, Canada
    Admin on the D*A*M Forum
    Dave, I have a bunch of 12AX7 preamp tubes you can try in your amp. That way, you'll know whether that's what you need or if it's something else.
    Give me a call (you have my #)

    You can also get them in Canada from http://www.thetubestore.com or http://www.leeselectronic.com

    Sovteks, EHX, and JJs are pretty good and no more than ~$15 each.
    Last edited: Jan 4, 2015
  17. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Tapping or prodding the valve with a chopstick can tell you if its the issue. If a prod rather than a tap makes noise, might just be a dirty/corroded pin/socket, that sometimes does that, clean or just a pull out and put back in can fix it. Free to try.
  18. Relsom

    Relsom Supporting Member

    Nov 23, 2013
    The Old Dominion
    Yup, ABM = Tube Pre, MAG = SS.
  19. OP: i once experienced the same symptoms, it turned out to be the dying battery in my instrument.