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Early 70's vs. Mid 70's SVT...same circuit?

Discussion in 'Amps and Cabs [BG]' started by Chris Breese, Mar 20, 2006.


  1. This may be a dumb question, but are there any differences in the circuits of the original early 70's SVT and the mid to late 70's SVT? Are they basically the same amp except for the looks?
    Thanks
     
  2. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    There were three different power transformers used - one for 6146's and two for amps that came stock with 6550's. The early 70's heads ('70-'71 or so) with the first generation 6550 PT had a little more plate voltage (~695V) than the later ones (~660V). Other than that, there are a few slight differences with plate resistors (5 ohms versus 10) and the current clamping diodes in parallel with the screen resistors.
     
  3. Thanks!
    I wonder how much difference all that has on the sound...?
     
  4. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    Probably not a whole lot. Most of the SVT tone is in the preamp, so the sound should be there as long as it's stock, up-to-snuff, and hasn't been modded for 12AX7's.
     
  5. In the preamp? In place of the 12DW7s?
     
  6. Rickenbackerman

    Rickenbackerman

    Apr 17, 2001
    Laurel MD
    You got it!
     
  7. Thanks a bunch, Rickenbackerman!
    I just scored a mid '70's SVT from eBay and I was just wondering if there was much of a difference between the two.
     

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