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Can you remove Tubes from an SVT 2 Non-Pro to lower output? Is it safe?

Discussion in 'Amps and Cabs [BG]' started by Ryan Buck, Oct 30, 2016.

  1. Ryan Buck

    Ryan Buck

    Oct 30, 2016
    Can you remove Tubes from an SVT II Non-Pro to lower output? Is it safe for the amp?

    If you can, does anyone have links to a tutorial? I couldn't find anything specifically for bass amps on google.

    I love my SVT II, because its an absolute beast. However, in order to get the tone that I prefer, I have to dime it and boost like a guitar head. It sounds absolutely monstrous, but I completely drown out everyone else at that volume.

    I feel as though my only other option would be to go with the Ampeg V4B, but if I can avoid buying another head, that would be great. Plus, I like having the head in a rack.

    Thanks in advance!
  2. BassmanPaul

    BassmanPaul Inactive

    You can do this but you will have to adjust the load impedance to compensate for the missing tubes. having six output tubes makes matching more than a little awkward.

    I would just leave the amp be and look for an amplifier with lesser power.
    Aqualung60 likes this.
  3. Ryan Buck

    Ryan Buck

    Oct 30, 2016
    Aww. That was what I was afraid of!

    But, Hey. At least I already got the "all clear" from my wife to buy a new head right?

    Thanks for your input!
    BassmanPaul likes this.
  4. Get a smaller cab. I had one and thru a 4 ohm 115 I could crank that SOB till it screamed! (Vol about 11-12 o'clock).
    What cab are you using with it?
    Last edited: Oct 30, 2016
    McFarlin and Plucky The Bassist like this.
  5. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Try an external master volume. Should work the same on these as with the old V4 and SVT amps.
  6. brbadg


    Nov 10, 2006
    Turn the amp up the way you like it.
    Then use the volume knob on your bass to turn it down a little.
    You are too loud if you are drowning everyone out.
  7. primusfan1989


    Jan 17, 2005
    new jersey
    You probably should consult a qualified tech before doing anything like that, better yet just get a smaller head if you need less power. Have the incorrect amount of power tubes in there is a good way to fry something else down the line (output transformer). People try doing the same thing with fender twins, take half the tubes to quiet it down, Ive seen a couple of them fry their amps and it ended up being pretty catastrophic for the amps and those are only 80watt amps so keep that in mind when you're thinking about doing this to a 300watt amp. Again, consult a good tech on this topic
  8. hbabels

    hbabels Supporting Member

    Jul 26, 2015
    Phoenix, AZ
    Another option would be a power soak or attenuator.

    One of the guitarists in my band uses one & it's great.

    Rivera Rock Crusher , Marshall power brake , & rocktron power soak to name a few. They're popular with guitarist who basically have same issue with tube amps

    They sit between Amp & speaker can & let you drive the amp hard & then dial back the actual output volume.
    Plucky The Bassist and msiner like this.
  9. anderbass


    Dec 20, 2005
    Phoenix. Az.
    Ryan, I've been gigging my SVT-II non pro for 10 years now and had the same exact Issue, get a Sansamp VT pedal. With the right settings, It'll get you very close to that same cushy, slightly compressed feel and tone at any volume.

    Another option is to engage your EQ section, (leave all the frequency sliders centered if you want) and try some of the lower settings of the Level slider on the far right. It'll attenuate and act as a Master volume knob, giving you the option of cranking up your Volume knob to add grit from overdriving the preamp section, but It wont give you that magical cushy feel & vibe of playing too loud or using a VT pedal.

    I see your new here, check out this thread:
    Ampeg SVT-II appreciation thread

    PS: you'll find some info (from psychobassguy) on why pulling tubes from an SVT is a really bad Idea, in my old thread at this link: SWITCHABLE MAX OUTPUT MOD, FOR a 300/w TUBE AMP.
    Bass 45 and RiZzBot like this.
  10. mpdd

    mpdd neoconceptualist

    Mar 24, 2010
    maybe try a bass with low output pickups, sometimes i do that for practice in my house
  11. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    None of those mentioned - nor any other commercial attenuator I know of - are designed to handle 300 watts.
    kosmicwizard and Jazz Ad like this.
  12. Smaller cab. crank it. or a VTBass pedal . or both. done.
  13. primusfan1989


    Jan 17, 2005
    new jersey
    Another thing to consider is a boost or an OD of sorts
    Power soaks and attenuators are not good for your power tubes, you'll cook them faster than with normal operation and those things are expensive to re-tube

    Your best recourse is a small tube head or a vt bass pedal IMHO
    kosmicwizard likes this.
  14. hbabels

    hbabels Supporting Member

    Jul 26, 2015
    Phoenix, AZ
    Definitely true about lulling your power tubes quicker & I didn't realize the common ones couldn't handle 300 watts that's an important point !! :)

    I also recommend VT Bass pedal or DI Peda if you want a blend knob extremely tube like & flexible drives Amps very well.

    Also might try a clean boost like MXR micro amp to drive input hitter of amp.
  15. okcrum

    okcrum in your chest

    Oct 5, 2009
    Verde Valley, AZ
    RIP Dark Horse strings
    Unfortunately, this "mod" is the same as pulling tubes as far as impedance matching goes.

    EDIT: more explain

    I have done gigs in a pinch with 4 output tubes in an SVT-CL, without damage. The output impedances rise by about 50%. It's only a little less loud, though.

    If you have to have tubes in a rack, I'd just get a pedal.
    Last edited: Oct 31, 2016
  16. Plucky The Bassist

    Plucky The Bassist ZOMG! I'm back from the dead!

    Jul 30, 2010
    Houston, TX
    Very good idea.

    OP, it would definitely be cheaper to find a low-sensitivity, 8-ohm 1x15 than to buy a V4B head. You could even go with a 1x12 if you propped it up on something. Just make sure it can handle that much wattage or you might shred it to pieces.
  17. Or even a 4 ohm 115. 's what I had. Now I use a Fender Super Bassman which has a 8/4/2 ohm select switch. So I'm good with a single 8 ohm 115. And it handles MOST of what I'll give it. Definitely get the Super Bassman into power tube break up a little. . or maybe that's the 115 stressing :woot:. Still. ...sounds good & and keeps doing so. With 2 of the Bassman Pro Neo 115 cabs it's a whole different situation. MUCH more volume and I'd have to be WAY loud before the power tubes start to cry:thumbsup:
    Definitely shows what more speaker cone area will do for yr volume! One 115 will sound great but let me drive the amp harder. i.e. ankle to get a little power tube break up. ..less CLEAN toob tone.
    2 x 115s YOOOOOOOOJ volume and earth moving levels before tube break up. i.e. lotsa CLEAN tube tone.
  18. Boot Soul

    Boot Soul

    Feb 10, 2009
    I have a SVT-II NP and similar to the suggestions of using less speaker, I got more drive with low efficiency speakers. I have used two 4x10 cabs, a Bag End (originally 8 Ohms, re-wired to 2 Ohms) with an SPL of 103 dB, and an Acme (4 Ohm) with an SPL of around 96 dB (I think). The matchup with the Acme has me turning up quite a bit more to get the same volume as when coupled to the Bag End, and as a result is a more overdriven, growly tone. Many Ampeg cabs are also not super efficient, maybe by design, and might behave more like my Acme than my Bag End. Just a guess, I've never used Ampeg cabs with my amp. It's weird that I found my Acme to be such a good matchup because when I originally got that cab I did not own the SVT and was actually going for a cleaner more hi-fi sound, powering it with a Crest CA9.

    Another idea could be trying to roll lower gain preamp tubes in any/all of the first three sockets. I put a 5751 in V1 and V2 which seems to allow for a bit more tube saturation at a similar output volume than when using the specified 12AX7 tubes in those sockets. I have read somewhere on TB of SVT owners using a 12AU7 in V1, trying to achieve similar results.
    Last edited: Nov 1, 2016
  19. Bass 45

    Bass 45

    Jun 23, 2011
    Tempe, Arizona
    If you want to stay with one amp, I think the SVT-2 Pro would be ideal for you. It has Drive and Gain knobs. you can get heavy distortion at speaking levels with that amp if you want to - and it sounds just like the non pro - if you want it too.
    anderbass likes this.
  20. Bass45, my experience is different than yours regarding your last comment and my side by side comparison of the ll NP and the 2 PRO, in two specific ways. 1) I couldn't get power tube distortion out of the 2 PRO at speaking levels regardless or settings and 2) I couldn't get the 2 PRO to sound like my favourite settings on the II NP either. Cheers.
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