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    KT88 vs 6550

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    Greg_M

    Posts : 40
    Join date : 2010-09-18
    Location : Poulsbo, WA

    KT88 vs 6550

    Post by Greg_M on Fri May 27, 2011 8:04 pm

    Probably this has been beat to death and I just can't find it, but is there really any operational difference?

    Bob Latino
    Admin

    Posts : 2375
    Join date : 2008-11-26
    Location : Massachusetts

    Re: KT88 vs 6550

    Post by Bob Latino on Fri May 27, 2011 8:50 pm

    Hi Greg,

    This has been brought up before and other's may have a different opinion but here is my take on the situation ..

    1. KT88's can nearly always be substituted for 6550's and vice versa.
    2. KT88's cost a little bit more than 6550's.
    3. KT88's can stand a little more voltage than 6550's and *may* be more durable in amps with a very high B+ voltage.
    4. As far as sound goes, IMHO, most 6550's have a "tubier" sound than KT88's with perhaps a little more mid-bass content. KT88's generally have a little more output at the very frequency extremes (top and bottom).

    Which tube is best for your amp (and system) is probably dependent on your musical tastes and the components you have in your system. Neither tube is "always better" than the other ..

    Bob

    j beede

    Posts : 316
    Join date : 2011-02-07
    Location : California

    Re: KT88 vs 6550

    Post by j beede on Fri May 27, 2011 10:00 pm

    I think the KT-88 is good for 200V higher plate voltage than a 6550. If you replace your 525V-rated quad cap with high(er) WVDC rated caps you could then safely replace your 5AR4 with a silicon bridge rectifier and run KT-88s in your Mark III. I am in the process of trying this configuration.

    Greg_M

    Posts : 40
    Join date : 2010-09-18
    Location : Poulsbo, WA

    Re: KT88 vs 6550

    Post by Greg_M on Fri May 27, 2011 11:55 pm

    I will probably be burned at the stake for saying this but.....I have a McIntosh MC275 that I have had for several years. I have never replaced the tubes. It currently has some 6550s. The only printing I can make out of the tubes is "6550 made in the USA" Eventually, I know I will have to replace them. My owners manual says either 6550s or KT88s and that's why I ask.

    I had a pair of ST70s that I ran in mono (one per channel) until I got the Mac and I still have one of them. Personally I don't hear that much difference (more sacrilege) in the two, other than the ST70 might have a little more emphasis on the bottom end. I also have a MK III Dynaco in the form of a Sunn 200s bass amp which I use KT88s in.
    I just wanted to make sure I would not hurt the Mac sound quality or even worse....hurt it physically.
    Obviously I am not interested in huge volume or breaking down walls. More....sonic clarity and transparency.
    You know, quality vs quantity.

    I love analog.....

    j beede

    Posts : 316
    Join date : 2011-02-07
    Location : California

    Re: KT88 vs 6550

    Post by j beede on Sat May 28, 2011 12:36 am

    Hard to imagine a situation where KT-88 would not be a safe/reasonable replacement for 6550. Going the other way, if your amp runs high B+, could be a problem for the 6550s. My VTL amp runs 650V B+ running "fake" Mullard EL-34.

    Westy56

    Posts : 58
    Join date : 2011-05-09
    Location : Albuquerque

    Re: KT88 vs 6550

    Post by Westy56 on Sat May 28, 2011 11:36 am

    Greg_M wrote:Probably this has been beat to death and I just can't find it, but is there really any operational difference?

    I have two indentical amps. One runs 6550's, the other kt88's.
    Both tubes are SED. They bias quite differently.

    The only thing for sure in my setup is the kt88's put out much better low bass.

    Regards,


    Steve

    j4570

    Posts : 141
    Join date : 2010-08-30

    Re: KT88 vs 6550

    Post by j4570 on Sun May 29, 2011 8:26 am

    "I will probably be burned at the stake for saying this but.....I have a McIntosh MC275 that I have had for several years."

    To avoid any burning at the stake, you can send that MC275 to me for proper "disposal".


    jdm

    Posts : 45
    Join date : 2011-04-04

    Re: KT88 vs 6550

    Post by jdm on Tue May 31, 2011 9:21 pm

    The New Issue KT88 Gold Lion's or the Tung Sol 6550's would sound great. The Gold Lion KT88's are very musical in my system and and compare very close to the Tung Sol KT-120. That Mac 275 is a nice amp, I would assume it is bullet proof if the caps are in good shape.

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