Recommend a 2203 mod with certain restrictions.

Discussion in 'The Workbench' started by Matthews Guitars, Nov 7, 2019 at 1:38 PM.

  1. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I love my 1977 2203. It's a great sounding amp. But I couid wish it had more gain and sustain. It really does not do singing sustained notes very well. And that's with the hottest preamp tubes I can find for it. Even with a 20 db input boost via a Seymour Duncan pickup booster pedal.

    I just want it to have more drive. And yet I don't want to do any irreversible mods to it. No holes drilled. No added tube sockets.

    I also don't want to lose it's touch sensitivity, where it can go from clean to raging by a change in pick attack or turning the guitar's volume knob.

    So that places some serious constraints on what mods I'll allow to be done.

    Since I really don't have a lot of experience with various Marshall mods, personally, I'm asking for your opinion.

    Within the constraints I've set, what would YOU do to try to get more gain out of this amp?

    I do not expect to reach the kind of liquid smooth gain levels that would come with adding another tube and two gain stages. But there has to be something that will help.
     
  2. myersbw

    myersbw Well-Known Member

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    Well, you're not going to get extreme results (like David Hopkins' overhauls) without ruining the value of a nice vintage piece. You can roll tubes through and see bits of change. However, there's one completely reversible mod that can start to kick it even further by driving the phase inverter harder and that's to add a PPIMV (post phase inverter master volume). Regardless that it already has a master, this one lets you push the standard master up...drive the PI harder...but, keep the overall volume dialed back.

    You want any competent tech...a 1Mohm PEC 2 watt pot...and willing to pull the front panel 'Lo' jack to insert the pot into a jack hole most of us never use. No other parts are removed and it can further fill the gap you're looking to close in regard to increased clipping.

    There are three common types of PPIMV circuits you'll find. I use the components mentioned and use the Trainwreck-style PPIMV Type 3. Search and you'll find a dozen drawn up or more. Some other variations may provide a more loved lower volume level of tone vs the Type 3, however...the Type 3 is more stable in regards to safety and ease of install where room is tight. I generally install them in the front when I can and use single, sold core, cloth insulated wire twisted for the connection...usually no other need for extra strapping is required with solid core. I've had no noise issues with that either.

    A good tech will have it done in about 30 min or so including chassis removal. Do NOT skimp on the 2 watt PEC pot! :)

    Give it a try...very inexpensive gain boost. I've done quite a few in SW Ohio and the only time I've been asked to reverse it is when the owner decides to sell it.
     
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  3. herbvis

    herbvis Active Member

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    just swap the 10k for a lower value and or bypass it with a cap for a bit of a boost
     
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  4. pedecamp

    pedecamp Well-Known Member

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    You have an aversion to pedals? Throw an SD-1, TS9, or RAT pedal in front and youre done, unless youre looking to do surgery on your amp, then do what Brad suggests or do a one wire mod or both. :yesway:
     
    Last edited: Nov 7, 2019 at 11:20 PM
  5. wakjob

    wakjob Well-Known Member

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    ^
    Agreed...at least with an OD pedal there's some way of adding clipping/compression as opposed to just slamming the input with dB's.

    My answer...wrong amp.
    Been there, done that.
     
    Drinkingdeath01 likes this.
  6. South Park

    South Park Well-Known Member

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    Just putting a pedal in the front end is a great idea. It is like adding a gain stage. The big benefit to that is the gain and tone stay the same in the amp.
     
    Jethro Rocker likes this.
  7. pedecamp

    pedecamp Well-Known Member

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    Right, he needs a JVM and sell me the 2203. :yesway:
     
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  8. Drinkingdeath01

    Drinkingdeath01 Well-Known Member

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    I was in the same boat with my JMP's, but decided like everyone else mentioned above that pedals are the best way. Don't hack a classic, your conscience will thank you later.
     
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  9. myersbw

    myersbw Well-Known Member

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    Yeah, minimal & reversible for anything regarding the amp. You won't hit beautiful metal-land without a pedal or extreme mods.
     
  10. neikeel

    neikeel Well-Known Member

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    My suggestions:
    Replace 470pF treble Peaker with a 2200pF silver mica.
    Lower the v1a cathode resistor to 6k8.
    You can also raise the v1a anode resistor from 100k to 150k, subtle but effective.
     
    Last edited: Nov 8, 2019 at 5:07 PM
    Guitar-Rocker and wakjob like this.
  11. johan.b

    johan.b Well-Known Member

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    Boss SD1 to the rescue....
    ... but if you have to mod, Google SIR34... you just tuck a number of components on top on what's in there. No need to cut traces or doing serious work, so if done cleanly is reversible... and no, it won't make everything you play sound like the artist named /
    J
     
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  12. Matthews Guitars

    Matthews Guitars Well-Known Member

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    All comments have been taken into advisement. For the moment I'm going to leave it be. In any event I won't do any mods that can't be completely reversed. I've kind of had an itch to scratch build my own amp anyway, so maybe I'll build one that suits this particular desire.
     
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  13. Rudy v

    Rudy v Active Member

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    How about soldano the hot mod
     
  14. Rudy v

    Rudy v Active Member

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    You can also use a kasha quick mod
     
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  15. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    What is the configuration that exists now?
    Have you tried different preamp tubes?
    Will you post some pictures of the preamp section?
     
  16. Matthews Guitars

    Matthews Guitars Well-Known Member

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    It's dead stock other than the addition of a Metropolous zero loss FX loop. I've already put the highest gain preamp tube in it that I can get my hands on, and that certainly makes a big difference but it's still well off from the level of gain needed to achieve liquid singing overdriven sustained notes. I'm thinking I'm going to experiment with gain stage plate resistor values and see how it responds to those resistors being increased in value up to maybe as much as 330K on a trial basis.
     
  17. NewReligion

    NewReligion Well-Known Member VIP Member

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    I addition to all mentioned above try a reversible mod. Remove one speaker out Jack to install a Friedman style SAT Mod on a DPDT Switch for added compression and clipping.

    David
     
  18. ampmadscientist

    ampmadscientist Well-Known Member

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    "...liquid singing overdriven sustained notes..."

    Would you really like to learn how to do that? It's not on any schematic.
    And you can do that with 100K plate resistors, no problem.

    :lol::lol: The fun is in the teasing, because only certain people know how to do that.

    I will give you a clue: it's in the layout of the circuit board. Not on the schematic.
     
    Last edited: Nov 10, 2019 at 4:37 AM
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  19. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    What kind of Guitar are you using?
     
  20. Drinkingdeath01

    Drinkingdeath01 Well-Known Member

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    Plus one on the Kasha quikmod. Kind of noisy but badass none the less.
     

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