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Ampeg SVT-CL Surge sound when fired up

Discussion in 'Amps and Cabs [BG]' started by Robert733, Mar 12, 2014.

  1. Robert733


    Mar 12, 2014
    Hello, I am new to the forums and would like to say hello!, over the last year I have recently gotten a SVT stack, I love it, sounds amazing, but I have been having a few issues with the head. When I fire the amp on to let warm up, and turn on the standby it makes a weird surge sound but the sound goes away and I am able to play withouth the sound happening again untill I turn it off. I Found a you tube video with my exact problem and was wondering if anyone knew what could be possibly wrong with it. Are my tubes going bad? Also I noticed when I play at loud volumes I hear a vibration of some sort from the tubes. :meh:

  2. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008

    The video helped. I suspect that you have a bad tube but there are other possibilities. When the amp is turned off standby, the high voltage (what is called B+) ramps up and hits the tubes. It is taking a second for the tube to stabilize when the voltage is not at the right level. This isn't normal.

    One solution is to try swapping out the small tubes that are in the preamp and on the power amp, one at a time. Preamp tubes are inexpensive so it wouldn't cost a lot to try. This isn't so doable with the power tubes. Since you can easily see the power tubes, when you take the amp off standby and are hearing the buzz, look for any odd flashing going on in the power tubes.

    The vibration that you hear could be a rattle of the retaining springs on the power tubes. One solution is to get a high temperature silicone tubing in the right diameter and slide it over the springs. This offers a cushion and stops the rattle. The tubing can be found at hobby stores.
  3. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Wow, first I ever heard that! Anyway, listen to beans. He can take an SVT apart and reassemble it before your very eyes within seconds! OK, maybe a little longer than seconds, but he's extremely good with SVT's. Does sound like it's tube related. Wouldn't go replacing them all or anything but I'd try to find the culprit. Might show itself as microphonic. You can take a chopstick or butt end of a wooden spoon or similar (don't use anything with metal on it for obvious reasons), turn it on and tap the tubes with the volume up a little, and listen for pinging, ringing or crackling sounds. I'd start in the back since most of the tubes are accessible there, but there are two tubes in the preamp...those 4 bolts on top just unbolt and it slides out enough to get to the tubes.