Strange noise coming from Ampeg PF-50T

Discussion in 'Amps and Cabs [BG]' started by Sound&Fury, Mar 13, 2018.

  1. Hi TB,

    Just got an Ampeg PF-50T. Great amp, love the tone! (Ampeg fanboy)

    However, after about 15 to 20 minutes of playing, the amp starts to make a sort of rattling sound. I recorded a short clip this weekend:

    (kids were in the room, that's NOT the sound I'm talking about ;))

    I have tested this multiple times and it's always after a bit of playing that the sound occurs and stays. So I presume whatever is happening is only happening when the tubes are fully warmed up.
    When I up the gain and volume, the sound gets triggered more easily but it's not necessarily louder. When the amp is not on top of the amp, the sound is less present but not totally gone. So I presume something is vibrating that shouldn't be vibrating.

    I have used the same cab (Barefaced Gen3 Super Twin) with my V-4B reissue, my PF-800 and Micro VR heads and never heard something like this before.

    Since it's a new amp, the most sensible thing to do is to just return it. But I'm not keen on the idea that the amp would be sent back an forth... So if there are some things I could check myself, I'd love to know them.

    Last edited: Mar 13, 2018
  2. Acoustic356


    Jul 3, 2014
    The most likely culprit may be a bad tube. I had a tube failure with my PF-50T within 45 days of having mine.

    I am sure the tube experts will be along soon...
  3. EatS1stBassist


    Apr 15, 2016
    So cal
    If it’s new return it.
    Old Garage-Bander likes this.
  4. Yes. If new, this. ^
    EatS1stBassist likes this.
  5. JxBass

    JxBass Supporting Member

    Aug 5, 2008
    When I got mine (new) it was making an odd noise. I found that the bias needed adjusting, after which it ran flawlessly.
  6. ahc


    Jul 31, 2009
    No. Virginia
    Couple things you can try: With the amp shut off and cold, remove the tube cage and reseat the tubes in their sockets. Be sure to put the tubes back in with the pins lined up with the holes in the socket. Tubes usually look like they have one pin missing and the socket has a wider gap for the holes. This is to ensure the tube is replaced correctly. Then leave the cage off, warm up the amp and play. If it sounds good, you just had a tube that wasn't seated all the way in the socket. If it still rattles, then take a non-metallic rod like a No. 2 lead pencil or wooden dowel and tap each tube. If the amp rattles when you tap a tube, that tube is bad and needs replacement. As @JxBass said, you should follow the directions and check the bias too.
  7. Most likely a tube. Do the pencil test..... with amp in operate mode, tap lightly on each tube with a wooden pencil... see if any sounds come out thru the speakers . Often it's one pre amp tube. . sometimes a power tube.
    Swap if you can.
    But. .. as it's new. . yeah. . return it.
    EatS1stBassist likes this.
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