The UN-official 4100 mods thread

Discussion in 'The Workbench' started by ampmadscientist, Jan 26, 2015.

  1. JWRE

    JWRE New Member

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    I'm unable to post sounds clips, as of now anyway, but thought I'd share my personal mods with the forum. Without sound clips I know it doesn't really help you decide whether or not to mod it, but to give you an idea of what I was looking for (and achieved) I'll share my taste in tone. I wanted a thick and heavy, yet also clean sound. I wanted that Marshall tone you hear at a live AC/DC or Slayer concert when they're cranked up. Something that sounded like an OD pedal was hooked up to, but wasn't needed for that thick tone. For those of you who run a patch cord in the Fx loop, imagine that much change plus more. A jumper plugged in there does nothing now. Here goes-

    First, install the R2 bypass cap. I went with a 6.8uf from the start. This alone will surprise you. Mine is a 50v with the +side on the leg of R2 facing the power amp board, and the - side soldered to the post labeled "SCN". Do not connect it to the other side of R2.
    My R37 ohm'd 8.2K so I left it alone.(from previous mod)
    Changed R33 to 10K
    Changed R7 to 6.8k
    Changed C25 to .1uf
    Jumped R54 with 390pf cap
    Changed R35 to 56K (didn't go with 68K because 56K was already in)
    Changed C8 to 100pf cap (a cheap ceramic disc type actually sounded best)
    Clipped C33,35,48 and R13
    Upgraded C5,15,37,38,39 to 400v
    Bypassed C11(not clipped, replaced with wire)
    For the slope resistor (R61) I used a 220k pot in place of the resistor by removing it and running the wires from the pot in their place. The plan was to adjust it to my liking, then put a resistor of that value in its place. Well, for me anyway, 220K was the best.
    To add a little more bass, you can strap R15 with a .0022 to .0047uf cap. I used a .0033.
    Plate voltage is 486 (was 472) and is biased to 42ma which is 68% with 30 watt tubes

    I hope this helps someone. I highly recommend these mods. And you can change certain values to your tastes, but you can't pick and choose certain mods because some of them work together. My Les Paul sounds amazing through it. The A channel alone has enough distortion to play most songs.
     
  2. cesar bogner

    cesar bogner New Member

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    people.. why so lack activity in this AWSOME thread??? OMG... no Pics.. no Video, no Sound Samples?? Cmon.... Good job and amazing iniciative ampmadscientist... keep going! and i dont listen to you im rookie wiring jaja but still does it!! if i dindt reply anymore is bocause i died xD.. i prefered Die by a Marshall and no by a heart atttack! regards!
     
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  3. solarburnDSL50

    solarburnDSL50 Well-Known Member

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    No worries my DSL brother. The clips I put here are all phone recorded. Nothing special and it doesn't have to be.

    I have modded amps and I have a JMP 2203 that is a straight up build of an amp to meet my wants.

    What I'm finding is I can tune my DSL40 outside of any mods and I haven't heard any one tone wise offer something I needed mine to do. However I realize our ears are different and I can't expect others to judge tones like I do. I do find words exaggerated in a lot of cases. That's why I like clips. Don't expect others to do the same.
     
    Last edited: Aug 13, 2017 at 2:55 AM
  4. solarburnDSL50

    solarburnDSL50 Well-Known Member

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    RIP.
     
  5. solarburnDSL50

    solarburnDSL50 Well-Known Member

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    Found a clip of me playing through my OR15...4 years ago. See what a goof I am...

     
    Last edited: Aug 13, 2017 at 4:48 AM
  6. tubes

    tubes Well-Known Member

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    Welcome Cesar.

    Well, it's an old and large thread... I'm sure there are clips in here somewhere....

    Personally, I have not felt a need to modify my own 4100.
    I am not looking for a perfect tone for a specific genre of music: I enjoy my 4100 for its grunt and versatility.

    But I have taken note of some of the things that the mad scientist has said.
    For one thing, he has mentioned some non-invasive tweaks that make the amp better.
     
  7. ampmadscientist

    ampmadscientist Well-Known Member

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    In your bathtub.
    You would be amazed at how this amp can sound....
    It will blow a boogie right off the stage.

    I would play it against any other amp.
     
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  8. tubes

    tubes Well-Known Member

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    Cheers mad scientist.
    Good to see you.

    As for "You would be amazed at how this amp can sound...."

    You don't need to convince me.

    I believe that some of the people who dislike this amp are not thinking in terms of a stage amp and a loud band.
     
  9. ampmadscientist

    ampmadscientist Well-Known Member

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    Oh, how that amp can roar...
     
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  10. tubes

    tubes Well-Known Member

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    Sometimes I think there is a good old fashioned 1960s Bassman hidden inside it: this might not mean much to the young people but I like it.
    Some Marshall lovers say there is an 800 inside it.

    Well that's two classic amps right there and we have not yet spoken about the 90s.
     
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  11. Rokinroller

    Rokinroller Well-Known Member

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    That is correct . From my experience with plenty 900 DR's , its when you start opening up some volume that the amp blooms with great bottom end and serious cut - through with Classic Marshall roar and punch ..... it really becomes a hot rod 800 then. Might be that Too many young bedroom wanna be's bought 900 series half-stacks to play in their parent's house bedrooms , got yelled at or thrown out when they tried to turn it up for a bit , cause then it REALLY shook the house in a scary way ... lol The 900's were meant to be played at decent volume ..... not bedroom levels. Applicable to most good tube amp power sections.... Especially 100 watters !
     
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  12. tubes

    tubes Well-Known Member

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    Cheers Rokinroller.

    We sometimes see threads in which people ask something like 'does anybody even need a 100watt amp?'

    I can only imagine that these questioners have not played with a confident and loud keys guy, or a heavy hitting drummer, or a band with numerous vocalists, or a band with numerous percussionists, or any band with any horns.

    Sheesh, the horns issue is kind of a killer here: I don't see people saying that they play in a band with four horns and the 5 watt amp or 25 watt is all they need.

    Meanwhile I'm not as stroppy as I might sound; I think of myself as eager to learn.
     
  13. Rokinroller

    Rokinroller Well-Known Member

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    Cheers Mr. Tubes , nice to see you still around here. Personally I do have some small wattage amps . They do have their place and I do like them when thats whats needed. They can still be plenty loud in a home studio . But man , nothing like a 100 watt's headroom in a band situation when required , its a good thing . I will say , I'm from the camp where there can never be "too many watts". LOL There are volume and master volume controls to tame the beast. Never a power soak for me either . Enjoy your powerful Marshalls .... its what our father of loud built them for !
     
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  14. tubes

    tubes Well-Known Member

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    I hope you stick around here too. We need reports from the front lines of all sorts of experiences.

    I am aware that it's good to have low watts on hand. (I can switch one of my 900s down to 25 watts. But that's as far down as I can go at present.)

    There is weirdness in this area.
    I have a memory... one time I said that anybody would want lots of watts in a guitar amp if that person had a horn section in their band.
    I received back the response that there is something wrong with this picture at the outset: nobody wants to hear horns these days: my thinking is wrong.

    But this cannot possibly be the final word about that!

    Meanwhile, for tonight, it's late and I'm tired.


















    f
     
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  15. liontato

    liontato Active Member

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    Love a live horn section. They will always be cool and wanted!
     
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  16. ampmadscientist

    ampmadscientist Well-Known Member

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    In your bathtub.
    4100 overview:
    The tone stack is designed like a Plexi, and the boost channel has a pre EQ which is fixed, you can't adjust it.
    Unless you modify it...but the pre EQ is also a lot of Plexi type EQ, it's still the same basic Plexi tone stack without the adjustment knobs.
    You see in my list of mods where I tweak the Pre-EQ design a little....
    Both clean and boost channels have diode clipping circuits. The boost channel uses LEDs for clipping.
    The clean channel is not really clean unless you take the diode clipping out. (which I did)
    The boost channel is where I left the LED clipping in, but some techs remove that. I liked the grind of the clipping in this amp.

    The major difference in this amp is that is has a lot more compression..which will also boost the noise from effects pedals.
    So if the effects has a lot of noise, you are going to get that noise boosted and amplified. Any effects needs to be tweaked until it's really low noise. (needs a really low noise effects power supply)
    Cheap noisy effects pedals do not work very well with this amp.
    AND for effects - you really don't want to use the channel input --but you want to use the loop instead.

    The effects loop won't match standard effects pedals very well...but that level can be adjusted / modified to match the effects if you want it to.
    (the stock loop level adjustment control is pretty useless, because of the design you can't really get the levels corrected.)
    When you turn the SEND down, it turns the return UP at the same time...etc...so it's hard to get it set just right.
    For some reason Marshall effects loops in general, never worked that great...
    That's really why we modified the effects loop levels.

    But on the + side:
    Once you iron out the bugs....it's quite a great Metal Amp!
    Has a very nice grind...great sustain...and when tweaked, it's pretty ferocious.
    I think it would hold up against just about any other amp, as far as Metal goes. It has a really nice smooth sustain for lead guitar.

    My other choice for Metal Amp would be: Mode 4. This Mode 4 amp has unbelievable grind, like a chainsaw on steroids.
    Quite a great Metal amp, I would say.
     

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