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V4BH Tube positions???

Discussion in 'Amps and Cabs [BG]' started by rodl2005, Sep 9, 2008.

  1. Can anyone tell me which tube is which in the V4BH PLEASE???

    I need a V1, V2, V3, V4 type list for the Pre amp tubes in it! There are 3 x 12AX7's & 1 x 12AU7 but I don't know which does what. I'm currently switching them about & noting what they do to the sound- I've some old Philips 12AX7's, a cuppla EH 12AX7's & an Aus. 70's 'Miniwatt' 12AU7 & 12AX7 The Philips 12AX7's give the V4BH a nice smooth overdrive compared to the Groove Tube Rebranded 'SOVTEK's that were in it.:)
    Any help appreciated.:help:
  2. BUMP/Smash/Grab
  4. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I just did a Yahoo search for a schematic that turned up nothing. That sucks. Maybe you should PM Jerrold Tiers.
  5. Jazzman


    Nov 26, 2002
    Raleigh, NC
    According to the schematic, the tube listings are split into preamp and power amp.

    In the preamp:
    "V1" is two early gain stages. 12AX7.
    "V2" is a post bass/treble gain stage, the final gain stage before the power amp. 12AX7.

    In the power amp:
    "V1" is the 12AX7 driver tube.
    "V2" is the 12AU7 phase inverter.
    "V3" and "V4" are the first pair of power tubes. 6L6GT.

    [My disclaimer: I am a mechanical engineer, not electrical, so my ability to interprit electrical schematics is probably far inferior to most people on this board. My only electrical training was in school. ...but the above should give you an idea of where the tubes are in the circuit.]
  6. Top of chassis:

    V1 is located towards the instrument inputs.

    V2 is located towards the power supply.

    Both are 7025/12AX7

    V3,4,5,6 6L6GC

    Inside the chassis:

    V1, 7025/12AX7, towards XLR, Pwr Amp In/Out jacks

    V2, 12AU7, towards connectors J10, J11

  7. umph. I thought you were talking about the v4b, but everyone was talking about the wrong tubes... I was just about to post a link to a v4 schematic when I realized that ampeg made this weird svt/v4 mix of an amp! I'm curious!! Anyone have a schemo they could send to me or post? I'd like to see the insides of this thing. Thanks!
  8. Yeah Me too would love a Schematics for the V4BH..???? anyone.
    Thanks for the replies so far guys!
  9. THANKS Jazzman!!!
    So would the Pre amp tubes-both 12AX7's be able to be ANY other valve??

    Also the DRIVER tube 12AX7 &/or the Phase splitter tube 12AU7 - can these be swapped to be say ALL 12AX7's or does it HAVE to be a 12AX7 for the driver tube, & have to be a 12AU7 for the phase splitter???????????

  10. bump a dump. Crump
  11. Crump is the Motor bike Speedway World champ!
  12. Well I tried out all the Different 12AX7's & 12AU7's I had & while it DID make a differece to the OD sound-the OLD phillips 12AX7 gave a much smoother OD than the Sovteks that came in the amp- The amp is STILL OD-ing earlier, sounding DULLER, & not getting to near the same overall volume that it did previously. Sounds like the terms described when you need to replace the POER AMP TUBES?????? NO???? I'll probly give it to my tech-so he can bias it, then see IF it does need four new 6L6GC's for the power amp.
    Any helpful info would definately be appreciated here!

  13. Got this. Also got my V4BH back today. My tech seems to think it should have 2 12AU7's in it-as the MANUAL describes-one inside & one where it's listed in the chassis.

    Mine came with ONE 12AU7- in the chassis-the PS tube AFAIK. The others were ALL 12AX7.
    Me tech reckons I should get a 12AU7 for the one inside the pre amp section(can't remember WHICH Pos. he said to place it, will ask him later.
    What do U think?????????
  14. BACK

    O O O O

    12AX7 12AU7***
    O O

    12AX7 12AU7 } inside
    O O } inside


    Does this seem right to any of U???? Thing is MY V4BH came NEW with 3 12AX7's & 1 12 AU7 in the **** marked pos. :rolleyes::help::rollno:

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