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"Rat Rod" Ampeg V4B

Discussion in 'Amps and Cabs [BG]' started by Chris 'Wighat' Jordan, Oct 22, 2013.

  1. Some of you may have been following my other posts on this and the DIY 2x15. I decided to do something different instead of restore this gem. Cheaper!

    Just finished this "Rat Rod Ampeg V4B". I got the guts out of a VT-22 (combo version of the V4), chopped the cabinet into a head box, converted the relevant components to V4B specs (the bass version), replaced every capacitor and resistor, converted the output stage to take 6550 tubes (formerly 7027), put NOS tubes in the pre and a matched quad of Svetlana's in the power section. Set the bias just right for plenty of clean headroom. I gigged with two guitars and drums and only had the gain on three (there's no master). Most all the tech work from my friend, George. Matching 2x15 cabinet to come.

    Attached Files:

    • V4B.
      File size:
      153.8 KB
  2. AdamR


    Sep 24, 2007
    Bethel CT
    Nice !
  3. Alex1984


    Jan 16, 2010
    Oh my, hope your 2 VT-22 speakers are still okay, they sound phenomenal, but the combo was simply too heavy.
  4. SirMjac28

    SirMjac28 Patiently Waiting For The Next British Invasion

    Aug 25, 2010
    The Great Midwest
    Nice job what color tolex?
  5. Did you take into account the vastly increased heater draw from the 7027, 0.9A, to the 6550, 2.5A??
  6. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    That's way too much work for me, but sounds like a fun project.
  7. Dig it! Great work.
  8. Forrrest


    Mar 10, 2013
    tell me more about this tube conversion. what OT did you put in there?
  9. The stock transformer is plenty stout for the heater draw. In fact, later production amps were alternately spec'd for 6550's. Obviously, Tolex-free. A change of resistors/bias was all that was necessary. Got the Amp without the original guitar speakers.
  10. I would have thought that Ampeg would have increased the heater winding spec for the 6550. In your place I would add a supplementary heater transformer to feed the output tubes. In my mind that's better engineering. Better safe than sorry.
  11. Gotchya, but we were able to determine that the transformer in this model was identical to the one spec'd in the later amps that could take 6550's.
  12. The cab is the exact width of the head and 8 cubic feet. I stayed with the two MCM 55-2983 drivers I already had. No mid-range or horn.

    It's made from the best plywood I could get here. 3/4" 10 ply cedar faced. Very few voids and those are tiny. Braced and glued with Titebond. 15 guage finish nailer and clamps.

    In the one pic you can see the tee nuts for the speaker and four extra for the grill clamps. I put them in with polyurethane construction adhesive as they tend to turn or pop out of their holes.

    I'll post some more pics as assembly progresses.

    Attached Files:

    • cab1.
      File size:
      133.2 KB
    • cab2.
      File size:
      155.9 KB
  13. Here's a couple more photos showing the hand holes for pulling the cab back on its wheels, the old school jack plate and then the finished cab with the amp on it.

    Attached Files:

    Tbone76 likes this.
  14. Cool - love the exposed wood look. Very nice and Rat Roddy.
  15. Thanks. I have a process for making new plywood look old and specifically like someone ripped the Tolex off thirty years ago. Here's an out-of-focus close-up showing the texture and another the installation of the amp feet cups.

    Attached Files:

  16. Mosfed


    Apr 21, 2013
    Chamonix Mont-Blanc
    Partner - CCP Pedals
    Very cool!

    Way beyond my capacity, and that makes me like it even more!
  17. Glad you dig it, couple more pics featuring the wheels.

    Attached Files:

  18. will33


    May 22, 2006
    Relic'd cabs......that's pretty neat. Cool work, man.
  19. BassCliff


    May 17, 2012
    So. Cal.

    I just wanted to say "Well done!" thumbsup. clap2.


    I'm digging it! Thanks for sharing.

    Thank you for your indulgence,

  20. Thanks, all. BTW, the cab is tuned to about 43 Hz, which is just above the Fs of the drivers. F3 @ 42 Hz, F10 @ 31 Hz. It would exceed Xmax pretty quick with a bigger amp, but it's perfect for this V4B. Cab could be more efficient, but enough clean headroom for small gigs without being in the mains and I am happy to report that it sounds really good.

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