6550 vs. KT88 tubes
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Sixtonoize
New member
It totally depends on the amp.
In my UL, 6550s are less stiff than KT88s, in my experience.
In other amps, you'll find the opposite.
In my UL, 6550s are less stiff than KT88s, in my experience.
In other amps, you'll find the opposite.
Ventura
Well-known member
titanamps":1axith81 said:you get em cooking, and neither of them are stiff.
KT88's were originally allocated to bass amps, believe it or not... The bounce a bit, have some liveilness to them, they can sound killer in the right amp. I've yet to get a lot of experience using them, the only KT's are 77's that I have had experience with - completely different animal...
6550's are in my Diezel, and they are by far one of my fave power valves of all time...in that amp, for the applications I want and use it for. Although Herr Diezel has now moved away from 6550's for reliability reasons, I still choose to use because they just rip. If they blow, which they have, I will simply replace with the same... I love 'em.
V.
aeroic
Active member
RJF":ko3ztw06 said:
And I view the exact opposite.
6550s to me have more of a EL34 mid-range...at least the SED =C= 6550s / old Svetlana 6550s (prior to the Svetlana trademark lapsing and becoming SED) that I have been using for years and years. I'm not a huge 6L6 guy outside of fender amps..and the SED =C= 6550s give me that warmth of a EL34 in the mids...with the bold bigger tighter bottom end and clearer top end...
mightywarlock
Well-known member
Old thread revival, but relevant to me...
Reinhold gave me some =c= 6550's to try out in my newly modded Twin Jet instead of the stock sovtek KT88's, and I'm currently going back and forth with the two types of tubes...
but I am having a somewhat hard time making a decision.
Can other folks out there see if i'm making any sense here?
to me, the KT88's seem bigger, and bolder, and clearer in their tone, whereas the 6550's seem to be a little more muffled, perhaps less mids, but have a little more grind to them.
However, he said to try dialing the amp in a little different, and I have, and it has made a difference, but since I can only play one tube type at a time, I'm having a somewhat hard time really being able to discern which is better.
do other people share the same type of opinions regarding the differences between KT88's and 6550's as I do, or am I hearing something wrong here?
Reinhold gave me some =c= 6550's to try out in my newly modded Twin Jet instead of the stock sovtek KT88's, and I'm currently going back and forth with the two types of tubes...
but I am having a somewhat hard time making a decision.
Can other folks out there see if i'm making any sense here?
to me, the KT88's seem bigger, and bolder, and clearer in their tone, whereas the 6550's seem to be a little more muffled, perhaps less mids, but have a little more grind to them.
However, he said to try dialing the amp in a little different, and I have, and it has made a difference, but since I can only play one tube type at a time, I'm having a somewhat hard time really being able to discern which is better.
do other people share the same type of opinions regarding the differences between KT88's and 6550's as I do, or am I hearing something wrong here?
Dale B
Well-known member
mightywarlock":25ksyua5 said:
Somewhat...
The amps I've swapped them back and forth in are the VHT Ultra-Lead, Diezel VH4, Diezel Herbert and various Marshall JMP 2203 amps that were either stock or modded. The Ultra-Lead is designed around these tubes, so my comparisons lean toward my experience with that amp because it's "truer".
Unlike the guy above with the UL, my experiences were completely opposite between KT88s and 6550s. Maybe he is using a different brand of 6550, but I used NOS GE 6550s in mine. The KT88s I used were Sovtek, EH, JJ and Valve Art (Chinese). All of these KT88s were definitely cleaner compared to the GE 6550s I had. Every KT88 had kind of an exaggerated vibe where it made the power section sound bigger in comparison to the GEs. All of these KT88s had a little give to them, but the GEs were stiff and more aggressive. The GEs definitely had that "hot-rodded 6L6GC" thing going on in spades.
I set the amp up like this:
V1 - Telefunken smooth plate Ecc83
V2 - RFT Ecc83/GE 12ax7wa/Chinese 12ax7
V3 - Same as V2
V4 - Same as V2
V5 - Tesla (not JJ) E83cc
V6 - Mullard 12at7
The 6550s in the Herbert made it sound a little more like the VH4.
KT88s and 6550s sucked balls in the VH4 I owned, but it was one of the earlier ones from around 2001. That amp was too HiFi sounding for those tubes in my opinion.
The main difference I heard in the Marshalls was just more headroom when swapping back and forth between 6550/KT88 types to EL34s. I still preferred the KT88 over the 6550 in Marshalls, but the differences between the two weren't as pronounced in those amps as they were in the UL or Diezels. The feel is different, but a 6550 feels a lot like a 6L6GC or EL34 in those amps.
Last but not least, the circuit design is going to be the biggest factor here. Some amps don't respond as well to tube changes as others. I just retubed my Soldano SLO with some NOS stuff, and there isn't much of a difference in my opinion. Also, we all hear things differently, and we use different guitars made out of different types of wood with different pickups. In other words, there is no right or wrong description when comparing tubes because it's just a subtle change. Those subtleties just so happen to be magnified by 1000% when we start to analyze things a bit too much.
YMMV
the4thlast1
Well-known member
I find 6550s to sound more aggressive than Kt88's
Kt88's have a big tight and smooth type of sound.
6550's are also tight but have more low mids and an angry kind of bark to them.
Hope that helps , its kinda hard to describe without actually hearing them for yourself. In my experiences I would say 6550's are a little bit like EL34's and Kt88's are a little bit like 6L6's.....However they have more differences than similarities.
Kt88's have a big tight and smooth type of sound.
6550's are also tight but have more low mids and an angry kind of bark to them.
Hope that helps , its kinda hard to describe without actually hearing them for yourself. In my experiences I would say 6550's are a little bit like EL34's and Kt88's are a little bit like 6L6's.....However they have more differences than similarities.
Dale B
Well-known member
Stramm8":23ngdzzn said:I always thought 6550s and KT88s were the same thing, just a different part numberKinda like 6L6 = 5881, 12ax7 = EC83 etc.
Nope! The KT stands for Kinkless Tetrode. The KT types tend to sound more linear than the other tubes in their "immediate family".
The funniest story I've read about them was something that Lord Valve wrote back in the day. He still may have it in his latest tube primer e-mail, but I haven't looked at them in a while. Anyway, the British made the EL34 power tube. The American power tube design to counter the EL34 was the 6ca7. After the 6ca7 hit the market, the British countered the 6ca7 with the KT77. The KT77 was the British version of the American version of the British EL34.
All of those types sound different from one another as well because they're all designed differently. The same can be said for the KT66 in comparison to the 6L6GC/5881 and the KT88 in comparison to the 6550.braintheory
Well-known member
I just did last week a massive shoot out in my Schroeder Dozer of my pretty much all the vintage 6550’s/KT88’s/KT90’s out there (other than Raytheon CK6550’s & KT88’s) and to me the favorite was the GE 6550’s followed by a tie of ‘60’s RCA 6550’s & Sylvania Coke Bottle 6550’s in 2nd place. JAN Philips 6550’s are also quite good. I seemed to prefer the 6550’s, but it might partly be that there just aren’t that many older KT88’s to choose from other than Mullard & GEC, which are very rare and imho very overrated (still very good though) and also Shuguang KT88’s (which I also like)
braintheory
Well-known member
I don’t know as much about non-vintage tubes. The winged c 6550’s sounded very good too (I liked the Svetlana Pre-Winged C 6550’s a little more), but the GE just stood out most with the most complex, rich tone. The ‘80’s JAN GE’s I didn’t like as much as the ‘60’s non-JAN GE’s, but they were a bit tighter sounding