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Tube Guys: 6550 vs KT88

Discussion in 'Amps and Cabs [BG]' started by Kelly Lee, Mar 29, 2005.


  1. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    OK, I'm thinking about changing the tubes out in my QuatraValve. It currently has four EH 6550's. I can't really afford to buy the big bucks NOS stuff right now and would like to try something different than EH's. I'm thinking of going to Bob at Eurotubes and having him send me some JJ KT88's and some new high gain 12ax7's.

    Here are my questions:

    Has anyone here done the 6550 to KT88 swap?
    Will I lose/gain power or be the same?
    How do they compare (generally speaking) sound wise to the 6550's?
    What other brands of 6550's or KT88's should I consider?

    Any input would be much appreciated!
     
  2. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    I spent a year or so researching these tubes. When my money got spent it was on a set of 8 Sovtek KT88 from www.tubedepot.com

    My second choice was the EH KT88/6550 (same tube I've been told by many sources). THe JJ weren't a choice because I already knew they weren't the end all for my head (what was loaded in it before I bought it... seller kept them for his SVT).

    for the pre I have 2x JAN 2x EH and 1x JJ 12ax7 as well as an EH 12at7. I'm real happy with my final choices.


    :bassist:
     
  3. Interesting. I arrived at the same conclusion... :bassist:
     
  4. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    What differences did you notice between the Sovteks and the JJs?

    Did you compare the two as well oddio?
     
  5. To my ear the JJ wasn't merely neutral but a bit flat sounding with the slightest midrange pronouncement. The Sovtek KT88 sounds fat, warm and more harmonically rich. As always, YMMV.
     
  6. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    I never heard the JJ in the head, I just was going off the sellers opinion...

    but I concur "fat, warm and harmonically rich" suit my head as well.
     
  7. BassGreaser

    BassGreaser

    Aug 22, 2002
    Austin, TX
    has anyone seen these SED™ SVKT88's What's their story? They look very good to me :D
     
  8. Those do look interesting, don't they? I know that the standard SED KT88's aren't as stable internally as many other brands and are prone to microphonics and rattling. The innards look quite a bit different in these cryo models however.
     
  9. DEVILMAN

    DEVILMAN

    Nov 24, 2001
    New York,NY
    How do the Ruby KT88's compare to the Sovteks?

    ~S~
     
  10. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    James and oddio, does this description of the Sovtek KT88 fit with what you guys have heard? I want a really powerful lowend.
     
  11. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    4 out of 5 techs I drilled with questions had less then nice things to say about winged C labeled stuff.... not the tone but the reliability. Enough to make me look elsewhere from the get-go.

    I know nothing of Ruby other then it is a tube distributor like Groove Tubes... their 6550/KT88 was not mentioned in ANY of the info I found, good or bad.

    If GE was still making their 6550 I would have bought 16 of them without a bit of delay (8 for now and 8 for the next decade)... everything I've read pointed to the Sovtek being the closest to the mid grunt & growl of the GE... My assumption through all I took in was the JJ are more HiFi (deeper, higher, tighter) with less interesting, dull mids.

    3 months in is too soon for me to have a legit opinion, Everything I say about tubes is assumption, opinion, deduction....

    but between the Sovtek KT88 and the EH & JAN & JJ pre, I'm in tone nirvana :smug:
     
  12. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    Christian reviews stuff for HiFi / Audiophile apps... so that is in playback on $20,000 stereo systems.

    IMHO/E if'n you want "powerful lowend" in a bass rig you gotta focus in the mid / low mid region.
     
  13. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    Thanks James and oddio for all the input.

    Maybe I will go ahead and try the Sovtek KT88 tubes (they are cheaper anyways :D ) for now.

    The one question I still wonder about is the power output of the KT88 vs 6550 tubes. Anybody know?
     
  14. protoz

    protoz

    Nov 30, 2000
    Iowa
    i've been looking up the same thing all day today because a Sunn Sorado I am picking up ($200 how could I resist) is coming with 2 KT88's in the power a british EL34, an Original Sunn tube and one the owner could not identify without taking the rear panel off.

    If these KT88's are a little weak I was looking at getting some Sovtek KT88's, they seem to have the most response and clarity of the whole lot next to the EHX's and maybe the Groove Tubes, but Ihaven't heard much about GT KT88's

    Anyone have any info on a KT90?


    From what I have researched the KT88 and 6550 are at the same power level (30watts I believe)
     
  15. Joe Martin

    Joe Martin

    Mar 23, 2005
    Frederick, MD
    They are 50 watts if I am not mistaken.
     
  16. protoz

    protoz

    Nov 30, 2000
    Iowa
    Each? Then why would the Sorado I am picking up be rated at 60watts with 2 KT88s? or is that just a very low safe rating they gave it?
     
  17. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    My QuatraValve is rated 220 watts and has four 6550's. That would indicate 55 watts per tube.

    However, LondonPower says that the 6550's are capable of 140-150 watts per pair (70-75 per tube) :meh: Its about 3/4 the way down the page on the FAQ section. From what I gather it has to do with the voltage the tube gets.

    Makes me wonder how powerful my amp really is, hmm.
     
  18. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    *I am no expert... never claimed to be*

    6550/KT88 in todays market are too similar to bother comparing type. I've been lead to believe the EH 6550 and KT88 are the same tube. Output is dependant on design and transformers... 30 to 70 watts a piece is the span I've heard. Most bass amps rate them at about 50 each. Trace gets 400 watts out of 6 and Sunn gets 60 out of 2. When the tech sets the bias they will also test the output. My Classic 400 with it's 8 Sovtek hit about 440. The KT90 and KT100 aren't consistent in my brief readings... my amp has a lot of power, I have no reason to try to milk it for any more :bassist:

    the KT88 and EL34 ARE NOT interchangable. I know the old Sunn heads came with a couple different tube types. I had a Sunn Sceptre from the early 70s that was stock with a pair of 6550 in it.