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Ampeg SVT VR Tubes Going Out

Discussion in 'Amps and Cabs [BG]' started by idkid1980, Jun 11, 2014.

  1. idkid1980


    Jun 11, 2014
    Hi Everyone,
    I'm new to the forum and in need of some help. I purchased an SVT VR amp in December and received the amp with a bad preamp tube. It came out of the box with a very strong sound like static. I contacted the company from which I purchased the amp, and they sent a replacement. Things have been fine until this weekend. I was playing a show, got through my show fine, but tried to turn the amp on for a friend to use and it kept having all sorts of trouble. The volume was in and out (with no punch to the tone), and once it did begin to sound ok but after playing for a few minutes it began to have a very loud sound, almost as if it was holding one note at full volume. The loud noise stayed no matter what volume I actually had dialed in. If it was turned on, then it was super loud.
    I guess my question is could this be another preamp tube going out or one of the larger tubes? Is it normal to have to replace tubes this often (I play on average for a few hours each week)? I tried different cables, basses, etc. to no avail. Also, I should say that I use a Y-cable for my input into the amp to utilize both channels. Could this be a problem?

    Thanks to whomever might be able to help me out with this issue!
  2. This does not sound like a tube problem to me.
  3. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    It doesn't? Kind of does to me, but admittedly I'm no tech.

    Tubes are funny...sometimes one can last years, and the one next to it on the assembly line can last a week. Doubtful all of them are bad, though. You can try pulling them out and reseating them and see if it makes a difference, or you can go through the amp while it's on tapping each one lightly with a chopstick or butt end of a wooden spoon (NEVER use anything with metal on it for obvious reasons), or you can swap each tube one at a time with a known good one of each type till you find a culprit. I think in your case, though, tapping them will reveal if you have a bad one. If not, it sounds like it's under warranty still (tubes aren't) so get in touch with Ampeg CS if you can't figure it out.
  4. The very-loud sound part tends to make me think it's not a tube, that seems a little out of the ordinary for a tube failing...to me.
  5. idkid1980


    Jun 11, 2014
    For the power tubes, does the tube glowing necessarily mean that it is working?
  6. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    A tube can be glowing and not work, some tubes don't glow because the coils are shielded. The part in the tube that glows when the amp is in standby is called the heater. Oddly enough, it's an element that heats the cathode inside the tube and allows the tube to work.

    Here are some symptoms of a bad tube: http://wiki.talkbass.com/index.php?title=Tubes#How_do_I_know_when_I_need_to_change_my_tubes.3F

    A fading in and out can very well be a sign of a bad tube. The squeal can also be tube related but it can also be an oscillation caused by something else. An issue with a power tube or a badly matched set of power tubes can send the amp into oscillation. You shouldn't use the amp if it is squealing. Have a tech look at it.

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