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Ampeg SVT-3 Pro upgrade tubes

Discussion in 'Amps and Cabs [BG]' started by disfiguredmetal, Apr 1, 2009.


  1. disfiguredmetal

    disfiguredmetal

    Sep 23, 2006
    here's a question for you tube enthusiast, i have ampeg svt-3 and i've had it for about 3 years and i got it used. now i need to replace the preamp tubes and i wanted some thing that i could get some nice warm tones out of with plenty of grid/ overdrive out of as well. does anyone know what kind of pre amp tubes i could use to spruce up my 3 pro?
     
  2. dose

    dose

    Nov 2, 2008
    Mobile,AL
    Hmm I to would like to know the answer to this one
     
  3. TheMutt

    TheMutt Guest

    Apr 28, 2007
    I've got a 4pro, but would love to know as well since it's essentially the same thing for when I eventually need new tubes. :)
     
  4. Martizmo

    Martizmo

    Mar 26, 2009
    Metro Detroit
    the phase inverter tube is the most important. This is the first tube in the chain and has most to do with your tone. I would still stick with the 12ax7 but maybe get a tungsol or other make. I am wondering if the other 2 tubes in the preamp stage are for the effects chain or eq, not to shure. Hopefully someone with more knowledge can fill us in.
     
  5. meatwad

    meatwad

    Apr 9, 2008
    Smallville, USA
    Preamp tubes are cheap, and I've thought about putting JJ's in my 3PRO for starters. They sound great in my CL.
     
  6. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Um..... well........

    The first three tubes in the 3 pro are in the preamp......... providing the gain, bright, ultra-low, ultrahigh, low and high eq, mid eq......

    The graphic is after them (if selected) , and is all SS.

    The power amp has two tubes, but no phase inverter..... They provide all the gain for the poweramp, with the 12AU7 directly driving the mosfet outputs.

    For preamp performance, the 3 tubes in the preamp would be the most important.......
     
  7. jimbilly

    jimbilly

    Apr 19, 2006
    I've always heard that V1 is the primary preamp tube for tone, but you'll have to find a schematic. I've never heard that the phase inverter has all that much to do with tone.
    I'm a big fan of pretty much anything old built in the USA, new or tests-good (used). I had RCAs in my SVP pro, you can't go wrong with those. Sylvanias and GEs are underated. Everybody is so hung up on NOS (whatever that means) that used tubes get no respect, but I've bought, and found lots of good used tubes that test new, but are much-much cheaper than "NOS".
     
  8. TheMutt

    TheMutt Guest

    Apr 28, 2007
    Uh... This is the 3Pro we're talking about here, right? I thought the power amp was solid state?
     
  9. MIJ-VI

    MIJ-VI Banned Supporting Member

    Jan 12, 2009
    NOS: New Old Stock.
     
  10. grimmchaos

    grimmchaos Supporting Member

    Nov 22, 2007
    Albany, NY
    The power amp is solid state, but 2 tubes send the signal into the mosfets.
     
  11. bassman_al

    bassman_al Supporting Member

    Apr 16, 2008
    Fairfax, VA USA
    Here is a photo schematic, with tubes labeled, of the SVT 3 Pro that I got from another TB thread. I am thinking of switching at least 2 of the tubes to JJ's... I hear tubedepot dot com is a good place to buy...

    tube schematic photo SVT 3 Pro.
     
  12. A SS power amp has outputs and drivers. A tube amp has outputs and a driver usually the phase splitter but it could have a buffer between the PS and outputs.

    The 3Pro has a SS output stage but a tube driver stage.

    As most phase splitters have a gain of one or even less they are not that important to tone shaping though you do need a good tube in that spot. Tube rolling may or may not give you any change whatsoever. It depends on the particular amplifier and on your ears. By all means try different makes of tubes and if you hear a difference great. I use Sovtek and JJ.

    Paul
     
  13. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Yep.....

    The 12AU7 is coupled direct to the Mosfet gates, and they provide only current gain, "matching" the 12AU7 to the speaker.

    So you get whatever the 12AU7 did, out the speaker.That explains the "tube gain" control that seems to be so puzzling to many folks (and sometimes not very effective).

    But the amp still has NO phase inverter........ The mosfets don't need one.
     
  14. 12bass

    12bass

    Jan 2, 2003
    Victoria, Canada
    Sorry to muddy the discussion, but would it be possible to increase the output amplifier gain somewhat by using a higher gain tube to drive the mosfets, say a 12AY7 or 12AT7? I ask because many people report that the preamp gain is insufficient to properly drive the output section in this amp without adding some boost in the EQ section.
     
  15. meatwad

    meatwad

    Apr 9, 2008
    Smallville, USA
    BUMP - To answer this question, please.
     
  16. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Jerrold,
    In addition to the above question, would you recommend Tung Sols as a good brand to retube a 3Pro?
     
  17. Metal Mitch

    Metal Mitch

    Jul 14, 2003
    NJ
    Ok, after reading the thread on biasing this afternoon my guess is you would need to re-bias the amp after making direct changes to the gain structure of this circuit. And we don't know if the required change in bias is within scope of the trimpot. So I wouldn't do it.

    Tung-Sol makes an excellent 12AX7 - I use em in my SVP-PRO and wouldn't trade em for anything else.
     

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