2203KK - should I choke it and depth knob it? update: done and done!

Discussion in 'Marshall Amps' started by Filipe Soares, Jul 3, 2020.

  1. Filipe Soares

    Filipe Soares Well-Known Member

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    Dear M'Fers,

    Due the extra time COVID gave me I started thinking about modding a little bit more my 2203KK. What are your thoughts about installing a choke and a depth knob?

    I mean love my amp, but better is always better. the question is would it be better with these mods?
     
  2. BanditPanda

    BanditPanda Well-Known Member

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    A good depth knobbing is always good Filipe but choking is not advised.:lol:
    BP
     
  3. Filipe Soares

    Filipe Soares Well-Known Member

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    I think I should do all of it while fingering Pia with Mr. Vai's consent... but I don't want to buy a Pia just to make this joke.
     
  4. South Park

    South Park Well-Known Member

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    Don’t do it keep it stock . Some day it will be a collector item . Looking at the schematic not sure if it will work right
     
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  5. Filipe Soares

    Filipe Soares Well-Known Member

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    Every mod I do I do it in a external box, I don´t like drilling holes in the back of the chassis. in the upper part I already did a 3/4 hole to pass the cables for the loop which are in a external box (future home of the depth knob).

    And I think this is my "ultimate marshall" and I have no wishes to sell it. I'm really not worried about the next owner.
     
  6. coolidge56

    coolidge56 Well-Known Member

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    ^^^ nailed it. :cheers:
     
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  7. Filipe Soares

    Filipe Soares Well-Known Member

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    my thoughts:

    about my cars: drive it like it was stolen.
    about my wife: fuck her like she is your mistress
    about my gear: mod it as you need.

    I don't care about the next owner, about her next husband... the next "owners" will receive some well used material!
     
  8. South Park

    South Park Well-Known Member

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    Go look at the schematic and I don’t see the same power supply as the 2204 . The choke and filter caps work with the voltage drop of the power tubes. It Is a big part of the Marshall sound . If the circuit is not the same you might not get what you want. I’m not saying it can’t be done you would be better off building a 2204 Clone with all the mods To see how these mods work . A big part of this biz is picking what to mod and build
     
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  9. Filipe Soares

    Filipe Soares Well-Known Member

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    there are lots of people who replaced the 470k resistor for a choke in the 2203KK. I have seen some videos and I really liked the result.
     
  10. South Park

    South Park Well-Known Member

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    It looks like it can be done .
     
  11. mad5066

    mad5066 Active Member

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    you won't know until you try, I say go for it especially since you can easily reverse it since you're not drilling holes. Maybe do a recording to A B it. A depth knob could be cool too.
     
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  12. Filipe Soares

    Filipe Soares Well-Known Member

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    that´s a great idea... installing a switch. will the choke/resistor interfere with the bias?
     
  13. mad5066

    mad5066 Active Member

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    If the choke has the same or relatively close to a DC resistance of the resistor than the bias shouldn't really change. If you do use a switch to compare I would make sure the amp is off first before switching settings just as a precaution not to damage anything. Since it seems like it's your main amp though you may notice a different feel immediately.
     
  14. Drinkingdeath01

    Drinkingdeath01 Well-Known Member

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    I had the same idea with my Soldano SLO. Had them do the depth mod and was excited about it only to be disappointed with the end results. I didn't like it all. Luckily when the mod is off its completely out of the circuit.

    Give it a try and let us know what your thoughts are.
     
  15. Filipe Soares

    Filipe Soares Well-Known Member

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    I have ordered a choke, when it arrives I´ll do both mods.
     
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  16. Marshall Boogie

    Marshall Boogie Member

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    My experience with chokes is they get rid of sag. If you love turning it up and feeling the amp sag don't choke it. If you love turning it up and staccato picking and hearing that pop of the initial transit then by all means choke away(that is seriously the only difference I got outta my chokes, it makes a little more power available at high volumes....hence sag goes away).
     
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  17. spacerocker

    spacerocker Well-Known Member

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    It's 470 OHM not 470K....

    This is the same mod that people do on the JVM410. Some people (like me!) also reduce the size of the filter caps at the same time for more dynamics (with a choke doing some of the active filtering, the caps don't need to be so big!)



    A choke will have a much lower DC resistance than the 470 Ohm resistor, so steady state plate voltage will increase slightly. For this reason it is worth re-biasing! It doesn't change by much, but is worth checking!


    A choke DOES NOT get rid of "Sag" (i.e voltage dip during transients) - it increases it! That is why adding a choke gives a more "classic", dynamic feel! During a loud transient, the rapid current demand change causes a transient volt-drop across the choke (that's how they work!) - causing the plate voltage to dip momentarily! For a "tight" feel with minimal sag - the stock resistor is the best option! For a dynamic, classic feel - choke is best!
     
  18. coolidge56

    coolidge56 Well-Known Member

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    Putting 500vdc across a switch isn't something I personally would do. A choke vs a resistor would not effect bias much if at all. Some HT voltage will drop across the resistor, not so much across a choke (one of the advantages) but probably a rounding error in the bias calc.
     
  19. mad5066

    mad5066 Active Member

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    @spacerocker is correct, I was only saying if you spec one than you wouldn't need to but more than likely the DC ohms will change thus requiring rebiasing. Or at least checking doesn't hurt to make sure it's around 70% in idle unless you like running it hotter.
     
  20. coolidge56

    coolidge56 Well-Known Member

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    Yes however choke resistance varies for a given choke. There's a Mercury Magnetics 10 Henry choke at 110 ohms, another at 210 ohms, and a Classic Tone at 270 ohms for example.
     

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