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tube amp mod question, a.k.a getting a good tube o.d. sound at low/medium volumes

Discussion in 'Amps and Cabs [BG]' started by Scott Lynch, Apr 22, 2006.


  1. Scott Lynch

    Scott Lynch Supporting Member

    Nov 27, 2002
    Delaware, USA
    Is it possible to install a switch that would allow a tube amp to run in half power mode? It would be nice to have an SVT or 400+ that could run at both 150w and 300w, to accomodate different types of speaker cabs and such, rather than owning multiple tube amp heads. I've heard that the trace elliot v8 could run at 200w and 400w, but i'm not sure if that is specific only to that amp design.

    Or, would it be smarter to just find a smaller speaker cab w/ high power handling for smaller/medium gigs?
     
  2. gwx014

    gwx014

    Dec 22, 2005
    Yeah, It's possible. I forget who but someone has a mod on their 400+ with a bunch of different power settings.
     
  3. Yes it is dooable

    A user on here has had it done to thier 400+, they have 5 switchs, when all are on its 300 watts, and with each switch you switch off the amp goes down 50 watts (it shuts down pairs of tubes)

    With an SVT you could do the same, but would only use two switchs, so when they are all on 300 watts, then each other one takes off 100 watts

    What you are looking to do is have a switch that will ground the cathode so that the plate volatges etc stay the same IIRC

    - Will
     
  4. BbbyBld

    BbbyBld

    Oct 13, 2005
    Meridian, MS
    If you turn off a lot of power tubes, the grid resistors may be too low for the remaining tubes...just an observation.
     
  5. anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    http://www.talkbass.com/forum/showthread.php?t=232820
    Heres the link to my 1st thread on this subject.

    This mod will work with any tube amp with 4 or more tubes.

    My modded amp is still working great. I can get all kinds of saturated power tube sounds at just about any volume level.
    The only drawbacks I've found with this mod are:
    (1) Cool sounding low wattage bass amps dont cut through very well with loud bands. (no big suprise there)
    (2) When gigging and recording at high gain levels, the side efect is a very hot and noisy balanced/DI output.

    Its not the mods fault. This amps DI signal is transformer balanced and goes though the power tube section. If I was to push a un-modded 400+ to the same high master volume settings, that amps DI would be the same hot and noisy signal.

    Next show I plan on running, f/x out(pre-only) to a DI box, Then to the soundman.
     

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