1987x LAR/MAR PPIMV mod

Discussion in 'The Workbench' started by Lespaulnmarshall, Oct 23, 2011.

  1. Lespaulnmarshall

    Lespaulnmarshall Well-Known Member

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    20 minutes ago I finished modding my 1987x. :)
    Tried it and it sounds pretty good to me. Haven't cranked it up higher than 8:30 o' clock for longer than a second, but I can say that at low volume levels it sounds better than any attenuator I have tried so far.

    Pics:

    Before starting:

    [​IMG]

    [​IMG]

    5K6 swamp resistors installed:

    [​IMG]

    Gnd5 and QR wires and 220k resistors removed! Bias wire installed:

    [​IMG]
    Installed the other wire:
    [​IMG]

    Under the PCB:

    [​IMG]

    Wires that go to pin 5 of the power tubes installed:

    [​IMG]

    Wired up the pot:

    [​IMG]

    Hole drilled in chasis:

    [​IMG]
    Ready to install the pot:

    [​IMG]

    Ready to put it back in it's cabinet:

    [​IMG]

    Done!

    [​IMG]

    :h5:

    Cheers! :cheers:
     
  2. hbach

    hbach Well-Known Member

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    Congratulations! Was this your first mod?
     
  3. Lespaulnmarshall

    Lespaulnmarshall Well-Known Member

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    Thanks!
    No, I've moddded my 800 before. I have done some mods on pedals and guitars too.
     
  4. Midnight Blues

    Midnight Blues Active Member

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    Nice job!

    Has anyone tried this on a 1959?
     
  5. Lespaulnmarshall

    Lespaulnmarshall Well-Known Member

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    Thanks, midnight!
    Many people have. Should work just as well as on my 1987. The mod is exactly the same, except that the wires that go to the power tubes go to V4 and V6 (there are jumpers between pin 5 of V4 and V5 and pin 5 of V6 and V7 on a 1959) instead of V4 and V5.
     
  6. hbach

    hbach Well-Known Member

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    I have it on my 2061 clone and it works great too. It just uses a different pot value.
     
  7. TradAmpGuy

    TradAmpGuy New Member

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    I have one on my 1959 clone and it kicks ass
     
  8. Neaves The Wicked

    Neaves The Wicked Member

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    Hi, I'm looking at buying at 1987x with the effects loop in the near future and would like to maybe have this mod done by a proffesional since I suck at this sort of stuff. Is there a schematic available for this?

    Thanks, Josh
     
  9. Neaves The Wicked

    Neaves The Wicked Member

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    Oops Nevermind. I did some more research and using this mod in conjuction with an amp having an effects loop is not the best. I guess it's OD pedals for room volume and cranked for the stage :)
     
  10. plexifier

    plexifier New Member

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    There shouldn't be any issue using a PPIMV in an amp with an effects loop. What concerns did you have?
     
  11. Neaves The Wicked

    Neaves The Wicked Member

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    I read a post here in the forum mentioning something about since the PPIMV mod uses the PI that when using the effects loop it would be distorted because the PI works with the Effects Loop? Unless I completely read it wrong.
     
  12. Lespaulnmarshall

    Lespaulnmarshall Well-Known Member

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    I can send you the schematic and manual I found if I can find it somewhere haha. PM me your email.
     
  13. Neaves The Wicked

    Neaves The Wicked Member

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    Awesome, Thanks! :)
     
  14. plexifier

    plexifier New Member

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    The effects loop is right before the PI and the master is after it so any effects should sound the same as they do without the PPIMV. You can make the PI overdrive a little more when turning down the PPIMV, mainly because negative feedback is reduced, but the overall sound from effects should be okay.

    I've never heard anyone mention any problems when using the MV with a loop. However, my amps don't have loops so I can't say for sure based on experience.
     
  15. jonzguitar

    jonzguitar New Member

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    Just wondering... do you use any modulation effects?
     
  16. Neaves The Wicked

    Neaves The Wicked Member

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    Oh Ok what you said sounds familiar to what I read. Yup I messed that up, :lol:

    Thanks Guys! :)
     
  17. RickyLee

    RickyLee Well-Known Member VIP Member

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    Good work!

    What was the cable and the gauge of it that you used?

    Did you use a dual 250K pot with the two 2.2MEG resistors?

    Did you use metal flame or carbon comp or carbon film?

    I want to try this mod on my '88 2205 as well.


    Regarding the FX loop together with a PPIMV? I have the LarMar PPIMV on my Ceriatone 2555 which has an FX loop. There's no issues there. But the Jubilee loop is a very different topology than most loops, as the Jubilee loop is before/upstream of the tone stack and before the last gain stage as well.

    The thing I've noticed with the PPIMV on the 2555, is that it is actually not all that useful. The Jubilee seems to actually get a bit harsher using the PPIMV and running the normal Master Volume up past 8. And the PPIMV negates the Presence circuit as well somewhat. I am actually thinking of removing the PPIMV on the 2555 and use the vacant hole to try something else. Maybe a Resonance control.

    :hmm:
     
  18. plexifier

    plexifier New Member

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    I use chorus occasionally but mainly just a couple of clean boosts. I have run a phaser and flanger in front of the amp and they sound fine. Just my opinion, but the only time you really need a loop is for reverb or delay when using a lot of preamp gain. I use an analog delay in front when clean or lightly overdriven and it works fine.
     
    jonzguitar likes this.
  19. Lespaulnmarshall

    Lespaulnmarshall Well-Known Member

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    1) I don't know I just got some decent size coax wire

    2) I used a 220K pot, and the 2.2 meg resistors

    3) carbon film
     
  20. RickyLee

    RickyLee Well-Known Member VIP Member

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    Coax cable like what is used on a cable box to TV?
     

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