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Ampeg SVT 2 Pro Valves

Discussion in 'Amps and Cabs [BG]' started by Slamms, Sep 11, 2019.

  1. Slamms


    Sep 11, 2019
    Hamilton Scotland
    I have an Ampeg SVT 2 Pro. I bought it in February 2018. The Output valves were changed in 2013 when 6 Winged C's were installed, I have the engineers receipt for this. Since the install the Amp has not had much use before I bought it and ive gigged it maybe 13 times since. I have no knowledge on when the other valves were replaced or what they are. The amp was serviced in March this year at a reputable service centre. The amp sounds great through my Ampeg 410HLF but would appreciate some guidance.

    Can anybody help on:

    1. How long I can should expect the valves to last? Am I already skating on thin ice?

    2. What other valves are recomended for the pre amp and how many are there.

    3. Recomended replacements for both.

    I play a Fender 57 re-issue precision with a quarter pounder and a Fender Mexican Jazz Bass with stock pickups. I play in a punk rock and roll band.

    Thanks for any help in advance.
  2. Wasnex


    Dec 25, 2011
    It's not really possible to say how long your tubes will last. It depends upon how frequently you play and how hard you push the amp. If you play infrequently at the low volume, the tubes could last for 20 years. Or the the amp could have a random failure at any time.

    If you regularly push the amp hard for several hours, the output tubes may wear out in a matter of months. The amp has six 6550s and there is quite a bit of disagreement over what is best. I suggest you use your Winged Cs for as long as they continue to sound great because they are fabulous tubes and have been out of production since 2012. It's a good idea to occasionally check the bias, as tubes change over time, so read your owners manual so you understand how to check and rebias the amp as needed. Current production tubes that people tend to recommend most frequently include JJ, Tung Sol, Sovtek, Shuguang.

    Preamp tubes can last for much longer than the output tubes. The amp has four 12AX7s and one 12AU7 in the preamp. It also has one 12AX7 and two 12AU7 down in the power amp section that serve as phase inverter and driver tubes. If you like the way the amp currently sounds, just use the same type of tubes that are currently in it.

    I would suggest buying a couple of spare 12AX7 and 12AU7 rather than a full set. If a problem develops that you suspect is a tube, then roll a fresh 12AX7 through the 12AX7 positions in the amp. If that does not correct the problem then you can roll a fresh 12AU7 through the 12AU7 in the preamp without concern.

    A bit of caution is required when swamping out the 12AU7 driver tubes because they control the bias of your 6550 output tubes. I would replace both of these at the same time, but before pulling the tubes reset the bias controls for minimum current in the output tubes. It's likely that installing new/stronger drivers will pull the bias down and cause the output tubes to conduct more current. So you want to turn the current way down before you install the new drivers, and then follow the bias procedure in your manual after you have installed the new tubes.
    JimmyM and Raw N Low like this.
  3. Slamms


    Sep 11, 2019
    Hamilton Scotland
    Thank you Wasnex, I really appreciate the advice.
    Wasnex likes this.

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