NAD- '79 Marshall JMP 2203

Discussion in 'Amps and Cabs' started by mix2much, Jan 19, 2015.

  1. mix2much

    mix2much Member

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    https://www.flickr.com/photos/129043797@N03/

    Came with 6550's. It was the best sounding JMP I could find in the area (I think I tried 5or 6 of them). I miss the power tube compression of the EL34s however and I think I might convert it. Has anyone done the conversion?
     
  2. sickboy79

    sickboy79 Member

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    Looks fantastic! That's a good year - I have a 79 2204, LOL! Amazing amp. Yours looks super clean.

    Yes, I converted mine to EL34s. I didn't do the work myself, had a tech do it. It wasn't pricey and was a quick turn around. Find a good tech and they'll do you right.

    Congrats!
     
  3. sixty2strat

    sixty2strat Member

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    I have 4 JMP 4 holers, 2 came with 34's one I changed and I left one with 6550 so I have 3 and one. In each did what the amp needed. The one was "not there" and needed the 34's to my ear a bit brittle and shrill.The other sounds so perfect that it's 6550's for life. Honestly they are both great sounds that NO one would ever mistake for non-marshall tones. Look if you thought it was the best I'd live with it and enjoy for what it is during the honeymoon period. Why mess with what sounds great
     
  4. custom53

    custom53 Member

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    I have a 1980 JMP 2203.. It is definitely a Keeper.. Pictured with a 1977 100 Watt Cabinet.. Mine came with 6550's and I had them changed to EL34's.. I like the EL34's better but really nothing wrong with the 6550's.. The EL34's seemed to break up a little quicker to my ears..

    Congrats on yours..!

    [​IMG]
     
  5. Sean French

    Sean French Supporting Member

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    Yes, have it converted back to original spec EL-34s.
    I have a March '80 JMP 2204 with EL-34s and it's glorious.
    Congrats. :dude
     
  6. Belmont

    Belmont Member

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    I wouldn't touch it if it sounds great as is, the EL-34 vs 6550 thing is way overblown, Hendrix used 6550's.
     
  7. TAVD

    TAVD Guitar Player Gold Supporting Member

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    Leave them. 2203's sound best with 6550 tubes, imo. You've got big iron and tons of treble and the 6550's help balance it all out. I tried el34's in mine, hoping to sweeten it but it just messed with the treble in a bad way.
     
  8. buddy7168

    buddy7168 Silver Supporting Member

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    Congrats! I have a '77. I did the el34 conversion and it was pretty easy once you get the board lifted. Of course don't forget to discharge the caps!

    [​IMG]
     
  9. Beng2040

    Beng2040 Supporting Member

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    Tons of treble for sure. I have my treble a quarter of the way up and it's still bright. I was thinking of converting mine (79 JMP 2x12 combo) to EL 34's but if it brightens it up more, I think I won't.
     
  10. tone?

    tone? Supporting Member

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    If its eating at you do the conversion. Its super easy and if you dont like it change it back.
    Any competent tech can do it.

    If you think it is too bright change out the bright cap on the preamp knob to 470pf instead of the 1000pf which is stock. That will take out a lot of the "unwanted" brightness and give back the lower end.
    Yes lowering that cap gives back lower end and a healthy dose of it as well.
    unless you are putting the preamp knob all the way up, in which case the cap is out of the loop.
     
  11. mix2much

    mix2much Member

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    The amp is not overly bright at all. It has a very good balance of tone. What I am more interested in achieving is more compression/sustain, which I get from my 2204 naturally. Of course the wattage is lower but I am thinking I can get a similar result by reducing headroom with EL34s.
     
  12. BADHAK

    BADHAK Member

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    I recently got a 79 2203 after being blown away by my 80 2203. Wanted to have a great backup and see if the 80 was a fluke.
    The 79 is pretty beat up and sounded abit tired. The previous owner had also snipped the bright cap. I mean, its still nice and was easily as good as my Ceriatone jcm 800 HW and my Landry, but not nearly as good as the 80.
    So i took it to the tech for new tubes, reinstall bright cap and a tune up.
    Man, i am over the moon....this thing just flat out rocks! !!! Is it as good as the 80??nearly, maybe. ...doesn't matter. ..i got a KILLER backup and the 80 was not a fluke.
    P.s. they both got 34s
     
  13. illini

    illini Member

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    I've had 6 different Marshall heads (2204's/2203's) run through my house over the years. They all were built between 78 to 83. Once I got them tuned up, they all sounded basically the same. Only difference was some would break up earlier than others, and this was due to plate voltage. I hear people talk about good ones or bad ones, but in my experience they all sound great once they are tuned up and running properly. Before that some were very bright, and some dull.
     
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  14. Schafrocks

    Schafrocks Member

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    Yep, even with the different tubes, you can dial them in to sound pretty much identical.
     
  15. mix2much

    mix2much Member

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    Thank for all the input. I did some knob twisting and really liked what I was able to get from the amp as is. I can always change it out down the road but for now it rocks as is.
     
  16. kramerxxx

    kramerxxx Member

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    What causes the dullness? I just played one that the owner said had new caps and tubes that had this dull, hollow tone that was lifeless.
     
  17. ronmail65

    ronmail65 Supporting Member

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    I agree. The difference is subtle at best. Personally, I prefer the 6550's in a JMP.

    Crank everything but Treble - start Treble at 0 and gradually increase to taste.
     
  18. mix2much

    mix2much Member

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    Just to update, I decided to do the switch to EL34s and I'm glad I did. It's not night and day different but just different enough the ways I was hoping. (Little bit more compression and mids)
     
  19. severinsteel

    severinsteel Supporting Member

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    How do you guys run your treble? For me, it depends on the cab/ speakers.
     
  20. buddy7168

    buddy7168 Silver Supporting Member

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    I keep mine at or a little above noon. That's going into 1973 pulsonic cone greenbacks (attenuated).
     

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