6550 vs. EL34 in Marshall JMP

Discussion in 'Amps and Cabs' started by drano, Sep 4, 2005.


  1. drano

    drano Member

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    Is there a noticable difference in the sound of the amp between these two power tubes?

    What is that difference?

    Does either make the amp more valuable on today's market?

    Thanks for the advise.
     
  2. 908SSP

    908SSP Member

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    The EL34 is more traditional and has a warmer midrange. The 6550 has a wider frequency response less midrange. This is a generalization because there are a bunch of exceptions between tube brands new and NOS. They are easily interchanged so it really doesn't mater value wise. Now a days I bet you find so many Marshalls that aren't original what tube is in there hardly mater's.
     
  3. sssmile

    sssmile Member

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    definitly el34's
     
  4. PUCKBOY99

    PUCKBOY99 Silver Supporting Member

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    I bought a '77 Marshall JMP MkII 2104 from a buddy of mine...all original with 6550 tubes.

    Prior to even hearing it, I had it set in my mind that I'd bring it straight to a tech for a rebias to EL34s.......

    Then I heard it:eek:

    ........Just a HUGE booming tone to it.

    Preamp up, it's true AC/DC...Thin Lizzy...all ROCKnROLL tone.

    But the surprise is how nice the clean is if you roll off the preamp. Dirty blues to almost bastard jazz clean.


    I see no need to change them.....I guess it's all personal taste though!:BEER:
     
  5. Scumback Speakers

    Scumback Speakers Gold Supporting Member

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    I'd have to agree. For the wider tonal response, I think the 6550's are the ticket. I tried out a dual 6550 setup in my prototype amp (single ended Class A type) chassis over two years ago. The clean was amazing, the OD was very fat. The EL 34's have their tone, too, no doubt, but overall I thought the 6550 was the more versatile tube.
     
  6. wyldefan

    wyldefan Silver Supporting Member

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    6550's are great but put in a JJ KT88's and they will rock you!
     
  7. JES1680

    JES1680 Silver Supporting Member

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    I love 6550s in my JMP. I tried the new GT 6CA7's and they are ok, but I'm going to go back to the 6550's as soon as I find a nice NOS pair.
     
  8. heybulldog

    heybulldog Member

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    +1 for the 6550's. got a set of GE's in my 82 jcm 4104 and i love the sound of that amp. people ask me about the mods i have done to the amp- its bone stock
     
  9. The Golden Boy

    The Golden Boy Member

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    Wow, it's interesting reading about people liking their 6550 amps. Most people on intarweb forums advocate changing them to EL-34s. I've got a '78 50w MV with 6550s that smokes. I wouldn't change anything about that amp.
     
  10. PUCKBOY99

    PUCKBOY99 Silver Supporting Member

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    Yeah, when I was about to get mine, all everyone said was change it to EL34s.....I wouldn't change a thing!


    BTW...nice to see ya' over here Golden Boy:BEER
     
  11. heybulldog

    heybulldog Member

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    Out of all the marshalls i have owned- jmp 50 watt non master 2X12 combo, Jmp 50 watt MV head, jcm 800-4104, 71 50 watt head and finaly my current 4104 only the 71 had el34s. I am sure most of the "marshall sound" i heard as i starteded playing in clubs came from the 6550's that people had in their jmps. - i dont think there was a lot of modding going around ohio in the late 70's and early 80's. so even though i think of marshall and el34s as the "thing" i think my reality is marshall and 6550's.

    if you read aspen pittmans' the tube amp book he lists mods for going both ways 6550 to el34and el34 to 6550 as he states that some people ( famous players) prefer the 6550 sound.

    said all that to say this: you can learn a lot from these boards but you also have to be carfull not to get caught up in the "party line". the good news is that i love marshalls with either tube set!
     
  12. drbob1

    drbob1 Silver Supporting Member

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    Amen, bro:dude :dude I have an 82 JCM800 with 6550s that sounds great and a Park Rock Head with EL34s that sound great! The Park is better for Rock and Roll in the basement, the 800 is better for stage where I can roll back the volume to get a very useable clean tone. People still ask me when I'm bringing the 800 back to our yearly jam session...
     
  13. JMP2203

    JMP2203 Member

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    i have tried a lot of power tubes(6550,kt`s,etc) in marshall and my vht 2502 poweramp, including NOS mullards EL34, and the winner for me is the 6CA7GE (nos, not gt), just amazing!,

    Clear, powerfull and warm!:dude
     
  14. jda

    jda Member

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    I love the sound of my JCM800 with GE 6550s - when it came time to retube, I specified the exact same tubes. They're great. They make you sound 3 feet taller.
     
  15. jhfire

    jhfire Supporting Member

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    I'm having the same dilemma. I picked up this Marshall 50W JMP MKII 78' all original except for the cabinet which was redone by Mojotone. The amp lacks bottom end. The treble is excessive IMO. I have the bass cranked and the presence and treble all the way down. Is this characteristic of the 6550 tubes in it? Or would converting to EL34 alleviate this? New speakers? Help!
    [​IMG][​IMG][​IMG]
     
  16. Anna_Laurel

    Anna_Laurel Senior Member

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    Yes.

    Deeper lows, tighter and firmer feel overall. Less prominent mids. More power. Excellent note separation in chords. More definition at high volume and high gain settings. It's more noticeable at higher volumes. The louder you play the more difference between the two tube types.

    Only to me.

    Most welcome. Meet my little monster:
    [​IMG]
     
  17. QRSS

    QRSS brutalist

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    if you're not willing to turn the master up to six or greater, search out the bright cap mod(snip).
     
  18. jhfire

    jhfire Supporting Member

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    Thanks! I'll try this.
     
  19. Trotter

    Trotter Supporting Member

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    I'm a huge fan of the SED Winged "C" 6550's in Marshall's.
     

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