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Question for Power amp tube Experts!

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  • Question for Power amp tube Experts!

    Hey all,
    I just bought a late 80's early 90's tube power amp off ebay the other day and it takes 6550s.
    My question is, what's the main tonal difference and output difference in a 6550 and a KT88?
    I've heard it has to do with low end and head room but is there anything else?
    Also!...What do you guys think of the soft/hard rating on power amp tubes that co.s like Groove Tubes have?
    I've alway been an EL34 man but I've owned several 6550 equiped Marshall JMP and 800 series heads in the past and liked that tone also.
    Would a "Soft" 6550 (1 thur 3 ,ala GT rateing) sound very similar to an average EL34?
    I'm not sure if I want to go with KT88s or a soft rated 6550 tube in this power amp to try and get more of an EL34 type of tone.
    Thanks for any help guys!

  • #2
    Most likely any power amp with either KT-88's or 6550's aren't gonna have much breakup. Unless you're viciously cranking
    that power amp, you may not notice much difference between soft or hard 6550's. If you want a more compressed tubey tone,
    you may have been better off with an EL-34 power amp, but
    I'd probably go with the type that the circuit was designed for
    which is 6550's. Otherwise, it's possible to run into a bias problem like the bias pot not having a wide enough sweep to change over to KT-88's. I'm not positive, tho. Just buy
    tubes that are the most highly recommended by your tube dealer for your amp. You didn't mention what amp it is?
    Originally posted by Boogie Bill
    I've got 60 guitars...but 49 trumpets is just...INSANITY! WTF!

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    • #3
      KT88's are heartier, because they can handle more current.

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      • #4
        Originally posted by Gearjoneser
        Most likely any power amp with either KT-88's or 6550's aren't gonna have much breakup. Unless you're viciously cranking
        that power amp, you may not notice much difference between soft or hard 6550's. If you want a more compressed tubey tone,
        you may have been better off with an EL-34 power amp, but
        I'd probably go with the type that the circuit was designed for
        which is 6550's. Otherwise, it's possible to run into a bias problem like the bias pot not having a wide enough sweep to change over to KT-88's. I'm not positive, tho. Just buy
        tubes that are the most highly recommended by your tube dealer for your amp. You didn't mention what amp it is?
        From what I've been told KT88's and 6550's are the same tube, like EL34's and 6CA7's are the same also (one being Euro. the other Amer.) I think it has more to do with a bias adjustment than anything.
        I already have an EL34 equiped power amp and wanted something different.
        The power amp I bought is made by a co. called Kasha. This co. is no longer in business and I haven't been able to find much info. on them on the internet.
        I also own some of there pre amps and love them. Thought I'd bid on this Power amp when I saw it on ebay and won it!
        I think I might go with some KT88's for a change!

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        • #5
          I was just reading a Q&A with Zakk Wylde in April Guitar World. He said he was on tour and his JCM800 went down and the guy that fixed it only had 6550's. So he rebiased it and and says the sound is fatter and tougher. Ever since he's been using Groove Tubes 6550's.
          Seymour Duncans I've owned: Dimebucker, '59n, '59b, PG+n, JB, Phat Cat, PGn, Custom, Seth Lover, '78.

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          • #6
            My JCM 800 Heads are from the early 80's, and they are stock. They run on the 6550's, and I really like em. More "Punch" than an EL34. I always thought 6550 was the U.S. Military # for the tube , and KT88 was the European Military #. Same tube, just a different number . Kind of like 12ax7 vs. ecc83 ????????
            Only The Strong Survive











            ________________________
            *Spina Pedal Mods Endorsee*

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            • #7
              My JCM 800 Heads are from the early 80's, and they are stock. They run on the 6550's, and I really like em. More "Punch" than an EL34.
              I agree. I like the compressed distortion characteristics and earlier breakup of EL34s, but for my purposes 6550s are the trick right now.

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              • #8
                Originally posted by 59paul
                My JCM 800 Heads are from the early 80's, and they are stock. They run on the 6550's, and I really like em. More "Punch" than an EL34. I always thought 6550 was the U.S. Military # for the tube , and KT88 was the European Military #. Same tube, just a different number . Kind of like 12ax7 vs. ecc83 ????????
                I've always like the "Punch" that Marshall JMP and 800 series heads have loaded with 6550's, but does anybody on the board have experience with the KT88's in Marshall heads or in power amps?
                Thanks for the comments!

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