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Loud Pop playing at low volume

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  • Loud Pop playing at low volume

    So last night sat down to play and about 20 mins in I hear a really loud pop like someone popped a large balloon in front of me. Was on the Gain channel and channel volume was low as was the master volume.

    So to say the least really caught me off guard and kinda scared the **************** out of me to say the least....nothing shut down and seem to be OK. Shut everything down to be on the safe side. At this point was expecting

    Prior to this happening I have been experiencing the Master Volume starting to crackle when trying to adjust it...also experiencing the volume fluctuating going from set volume to lower and then back up. I have suspect that PWR Tubes might need to be fact all tubes as they are the OEM tubes.

    Having said that first thing I checked were the Tubes and no cracked glass or burns. No burnt electrical smell in the amp head.

    Eganter Vengeance Head(60w - 120w)
    4x12 cab 16 Ohm
    Pre: Tuner->NS2->TS-9->MXR 10-eq
    Post: TC Electronics G-Major->BBE 382i

    So current thought are

    1- Bad Tubes
    2- Surge though the electrical circuit that was amplified through the head/cab?

    Any thoughts?

    - Ibanez MTM2(EMG-18Voltz) -
    - Mesa Boogie Single Rec -
    - Egnator Vengeance -
    - TC Electronics G-Major
    - Custom 4x12 Build DIY -

  • #2
    Its not a surge. The power supply would filter that.

    It can be a loose tube or an oxidized contact. What you can do is remove the tubes then wet the pins on the tubes with non lubricating contact cleaner (not the lubricating stuff designed for pots) or use alcohol then plug and unplug them a few times to clean the sockets. If the problem persists its likely a tube going bad and you want to change them before a catastrophic failure occurs.

    If the volume is turned off and you hear the popping its likely the power tubes. The problem is if it only happens occasionally its really tough to find the culprit. As a tech one test was to turn the volumes and tones up then tap each preamp tube lightly with a pencil. If the tube has become microphonic you'll hear a pinging sound or a crackly from the speaker. Other then that, you simply have to change them out.

    When tubes heat up the metal elements inside expand and when they cool they contract. In a combo they also vibrate from the speakers. Eventually the metal weakens and welds that hold screens and plates in place crack and start making bad electrical contacts. The crack you heard occurs when the high voltage path is broken or the suspended screens inside the tubes warp and arching occurs. The only fix is replacement.

    The problem can occur with new tubes too. Tubes get shipped long distance and can see allot of vibrations in transit. I Re-tubed my Bassman recently. I first tried a set of Ruby power tubes on sale and barely had time to bias them when I got a loud pop like you experienced. I immediately pulled them out and sent them back. I then tried a set of JJ's after biasing I heard light popcorn sounds in the background. Another set of duds, so I sent those back too. The next set I bought Electro Harmonics tubes which I now to be great tubes. I had replaced a set in my Music Man a year Earlier and they were excellent. I had no noise and they sounded great. I replaced all my preamp tubes with the EH too and it was like taking a blanket off the amp for tone,

    I did have Groove tubes in there which had lasted me a good 15 years and sounded very good. I don't use the head all the time and since its a head, not a combo I can get those kinds of mileage out of them. I developed a problem with one of the preamp tubes so I did the entire set. The EH rate the highest for low microphonics and noise and they have an excellent frequency response high for low noise plus the cost is excellent. You'd have to using something like Mullard black sable's and pay an arm and a leg to get similar results.


    • #3
      Master Volume starting to crackle when trying to adjust it...also experiencing the volume fluctuating going from set volume to lower and then back up.
      These are the classic symptoms of a dirty and/or worn out volume pot.
      This space left intentionally blank.


      • WRGKMC
        WRGKMC commented
        Editing a comment
        Pot wear is usually progressive and has symptoms of crackle. The crackle can be loud but rarely as loud as he describes. It can be a loose tube contact too, but something as loud as a balloon popping spells bad tube arching out in my book. The pots can be cleaned with lubricating pot cleaner to rule those out but I wouldn't wait around to find out if that pop occurs again. Next time the arching may cause more then a loud noise.
        Last edited by WRGKMC; 01-12-2018, 10:09 AM.