JCM800 4010 combo harshness

Discussion in 'Amps and Cabs' started by Renardm, Jan 15, 2008.


  1. Renardm

    Renardm Member

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    Do any Marshall JCM 800 4010 combo owners find their amp harsh when they crank the master to distortion? I don't have the bright cap clipped on mine and it gets real ice picky at high volumes. Would a power tube change help this?
     
  2. John Phillips

    John Phillips Member

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    Possibly, and it may also be biased too hot - the commonly recommended setting of 70% of tube rating is much too hot on these amps and makes them harsh and strident as well as eating tubes - 55% or so is much better. (And even lower if it's a 6550 model.)

    They also sound better with the negative feedback feed (the purple wire on the impedance selector) moved from the 4-ohm to the 8-ohm tap, IMO.

    It's probably nothing to do with the bright cap though, since when you're into power stage distortion most of the harmonics come from there, not the preamp.

    Which speaker does it have?
     
  3. Squigglefunk

    Squigglefunk Senior Member

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    my 4010 gets fatter sounding as you turn it up.
     
  4. Renardm

    Renardm Member

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    Mine has the original Celestion G12-70 speaker. I play it in a smaller room with low ceilings. I wonder if that has something to do with it. Plus, it gets way too loud when it is cranked. Maybe it just sounds harsh because of the volume.
     
  5. daddyo

    daddyo Guest

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    Hmmm, who'd have thought a 50w marshall would be too loud cranked - rock on, :dude
     
  6. Renardm

    Renardm Member

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    Yeah but it is not a pleasing sound. Just may be the nature of this amp!
     
  7. bosstone

    bosstone Member

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    It's not the amp. It's the speaker.
     
  8. RKHIII

    RKHIII Member

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    I never could get real close with my 4010 either so I traded out of it. It was way more amp than I needed for the house anyway. I'd probably side with Bosstone though that a speaker swap could be the ticket. I stuck a Celestion Century in my Marshall Studio 15 and it sounded considerably better to my ears than the stock Celestion Vintage 30.
     
  9. sundaypunch

    sundaypunch Member

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    I have to agree with you. I'm not a fan of the 70-watters. Along with the other tips I think that dropping a G12-65 in there would help.
     
  10. rockon1

    rockon1 Member

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    Maybe but the G12M-70 isnt a harsh speaker to my ears. Might not be the most colorful or toneful but I wouldnt call it harsh. A G12-65 might be smoother though. On the bising thing-


    Interesting coinicidence what John Phillips posted about biasing too hot. I just got thru lowering the bias on my Supersonic because it was harsher than I remembered before I set it hotter at 65% dissapation. I brought it down to 55% dissapation (right around 33 ma where the factory calls for it to be)and it smoothed out a good bit. Bob
     
  11. Renardm

    Renardm Member

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    Does adjusting the bias affect the overall tone and gain of an amp just when it is played at higher volumes or will you notice a change even at lower volumes(preamp dimed)?
     
  12. rockon1

    rockon1 Member

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    Well not sure about your Marshall but with my Supersonic it was harsher /more piercing as I turned it up-pre amp dimed or not. Lower "bedroom" volumes it wasnt as much an issue.Of coarse thats just my experience with this amp. Bob
     
  13. anibas

    anibas Member

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    An Eminence V12 would help things out considerably-I've used one in my 4210 combo for about 3 years now,and it helped tighten up the low end as well as smoothing out the high end a good bit.Overall,it makes my amp sound like it's running through a closed back 2X12 or 4X12.Try one out if you get the chance.
     
  14. vintage66

    vintage66 Member

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    Interesting-I read another review that said the same thing about sounding like a closed back cab. Has anyone compared it to a Vintage 30-that's what my 4010 has in it.
     
  15. HoboMan

    HoboMan Silver Supporting Member

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    I have the same speaker in my 4210 1x12 combo. I've been using it for over 13 years and just found out how bad the G12M-70 speaker really is.
    At the advice of John Phillips I used my Boogie F-30 with a V30 speaker as an extension cab.

    The amps sounded a lot fuller and got A LOT louder.
    Also at the advice of John Phillips I bought a Classic Lead 80 speaker for my Marshall. It came in today but I am out of town. Won't be able to put it in until tomorrow.

    The speaker may not be the main cause of you problem but I recommend changing the speaker first thing.
     
  16. joolzriff

    joolzriff Member

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    give it a go over....new tubes and bias at a tech's and a speaker swap...now for some more research.....what about a scumback?
     
  17. gldtp99

    gldtp99 Member

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    I hated the G12M-70 in my 4010----- i had a new G12T-100 laying around and it's an improvement---- besides eliminating the farty bass at high vol, it sounds better overall---- it might not be the #1 best choice but it's what i had on hand to try---- i also de-modded and voiced the amp to my taste----- i eliminated both treble peaking circuits, replacing with different value resistors. And a few other things.
    the previous owner had installed zoso tone caps throughout--- i didn't hear the amp before so i'm not sure if these are an improvement or not---- they are supposed to be.
    I still like this amp better when it's pushing a single 4x12 cab instead of the internal speaker but i'd play a show with the internal 1x12" G12T-100 with no problem................gldtp99
     
  18. rastaman

    rastaman Member

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    I have a Classic Lead 80 in mine and it is smooth. Where do you live? Jeff Andrews http://www.andrewsamplab.com/ here in Atlanta went through mine when I got it (it had a couple few mods for more gain, it was VERY noisy) and turned it into a rock and roll machine. It is loud, no doubt about it.
     
  19. Renardm

    Renardm Member

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    I live in Rhode Island. I know a small, local place that can bias some new power tubes that I received from Eurotubes. The next thing I will do is look for a new speaker bases on the suggestions here. thanks!
     
  20. HoboMan

    HoboMan Silver Supporting Member

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    OK, I replaced the G12M-70 speaker with a Classic Lead 80 in my 4210 combo and WHAT A DIFFERENCE!

    Much fuller & smoother sounding. A lot more bottom without the spikey highs and A LOT MORE volume.
     

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