TUBES, TUBES, TUBES

Lonesomedave · #1 06-25-2011, 12:07 AM

Hi, guys;

i am sorry if this question has been asked before, but I have not seen it.

what is the difference between 6550 power tubes and KT-88's?

are KT-88's just super 6550's? are they interchangeable?

ampeg uses 6550's as its power tube but i believe marshall and eden use kt-88's (correct me if i am wrong)

is there any more difficulty in getting replacements for one than the other?

also, does anyone have experience with the eden wtb-300 amp? i believe it has independent bias adjustments for each tube on it's back panel. is this true and how does it work? I am intrigued by this amp, because the cost is significantly less than either the ampeg heritage or the marshall vba-400.

i would appreciate any input from someone who has used one.

thanks,

/s/ Dave

JimmyM · #2 06-25-2011, 12:11 AM

6550/kt88 - Marshall Amp Forum

Lonesomedave · #3 06-25-2011, 12:28 AM

thanks, JimmyM;

from what I read on the site (and again, please, please correct me if i am wrong), any amp designed to run 6550's can safely run KT-88's, r..i..g..h..t?
/s/ Dave

johnk_10 · #4 06-25-2011, 12:38 AM

pretty much every one that i've seen. and BTW, marshall used 6550's in their 50 and 100 watt models that were sold in the USA. they used EL34's for the british versions, and KT88's in the marshall majors (200 watt)..

Mr. Foxen · #5 06-25-2011, 02:03 AM

KT88s draw a little more current and some Ampegs apparently don't deal well with that. They can also take higher plate voltage, which is only really relevant if your amp provides it. They are cleaner in an amp designed around them, but actual lack of distortion isn't generally what you are after if you run valve amps (clean like a PA, rather than clean set valve amp).

Edit: Data sheets here: http://www.drtube.com/tubedata.htm

staindbass · #6 06-25-2011, 07:09 AM

here is more info. Ampeg SVT 300W biasing - AMPAGE Archive i switched to kt88 in a mcintosh amplifier, didnt have to rebias, but ampegs may be different. why were you looking to switch? changing power tubes wont have as much sonic effect as changing preamp tubes. i switched simply because i am snobby and wanted the best tubes even if it only made a tiny tiny difference. vintage metal based gec gold lions.

staindbass · #7 06-25-2011, 07:12 AM

here are a bunch of opinions info. Search of Tubes Asylum

kander · #8 06-25-2011, 07:21 AM

Quote:

Originally Posted by Lonesomedave

Hi, guys;
what is the difference between 6550 power tubes and KT-88's?

In my limited experience, 6550's sound awesome in my SVT while KT88's sound super awesome.

staindbass · #9 06-25-2011, 07:25 AM

is that true kander? i didnt think most people would be able to tell. good news. bad news is i only have 4 and cant try them in my svt

staindbass · #10 06-25-2011, 07:30 AM

kt88 eye candy

kander · #11 06-25-2011, 07:42 AM

Quote:

Originally Posted by staindbass

is that true kander? i didnt think most people would be able to tell. good news. bad news is i only have 4 and cant try them in my svt

Probably not, but I need to convince myself after I spent some $$$ when it came time to retube

JimmyM · #12 06-25-2011, 09:07 AM

Quote:

Originally Posted by staindbass

kt88 eye candy

Wow, bet that's a hell of a "micro" rig

AwkwardLoudness · #13 06-25-2011, 09:10 AM

Quote:

Originally Posted by Lonesomedave

what is the difference between 6550 power tubes and KT-88's?

KT88s are cleaner sounding (more headroom) and draw a little bit more current compared to 6550s. The tone character of 6550s is a bit more fuzzy when the power section is overdriven. KT88s are more clear and articulate when overdriven.

Quote:

Originally Posted by Lonesomedave

are KT-88's just super 6550's?

I wouldn't characterize them that way. The two types are contructed differently. GE 6550A tubes are...uh.... "super" 6550s. KT120 tubes are super KT88s.

Quote:

Originally Posted by Lonesomedave

are they interchangeable?

Yes in some amps, but no not all. The power transformer in some amps will handle 6550s, but not the extra draw of KT88s. Any amp with KT88s should be able to use 6550s though. The bias needs to be adjusted appropriately swapping from 6550s to KT88s or vice versa.

I don't have any experience with the Eden WTB300V amp. KT88s are the stock power tubes, so one should be able to use 6550s as well...after a bias adjustment.

Quote:

Originally Posted by staindbass

i didnt think most people would be able to tell.

At loud volume with the power section pushed hard, you would definitely notice the tonal difference between KT88 and 6550s. Trust me.

JGR · #14 06-25-2011, 09:35 AM

Quote:

Originally Posted by staindbass

kt88 eye candy

Holy crap that is nice!

staindbass · #15 06-25-2011, 09:39 AM

Quote:

Originally Posted by kander

Probably not, but I need to convince myself after I spent some $$$ when it came time to retube

good answer. opinions are great but there is nothing like finding out for yourself.

staindbass · #16 06-25-2011, 09:44 AM

here is the whole micro rig

yes i hear the ge 6550a are something special. i would go for those first. at worst you could resell them for the same price you paid.

lowphatbass · #17 06-25-2011, 10:04 AM

My ears are NOT that great(in an audiophile kind of way) and I don't play my tube amps too often. Even so I find that in my Sunn the original Genalex KT-88's sound better than the modern replacements I've tried, I didn't think I would be able to hear/feel a difference but it's there.

rickdog · #18 06-25-2011, 10:27 AM

Quote:

Originally Posted by AwkwardLoudness

KT88s are cleaner sounding (more headroom) and draw a little bit more current compared to 6550s.... The power transformer in some amps will handle 6550s, but not the extra draw of KT88s. Any amp with KT88s should be able to use 6550s though.

Quote:

Originally Posted by Mr. Foxen

KT88s draw a little more current and some Ampegs apparently don't deal well with that. They can also take higher plate voltage, which is only really relevant if your amp provides it.

It sound to me like the answer is really "maybe" and "it depends." An amp designed for KT88s could have too high a plate voltage for 6550s. An amp designed for 6550s might strain to provide enough current for KT88s.

All things considered, I would expect it to be safer to substitute KT88s for 6550s. Run the amp under load and check for transformers overheating, you should be able to notice this before it would do any damage. Going the other way and putting too much voltage on 6550s seems like it would be more likely to cause a sudden, catastrophic failure that would cause expensive damage.

throbbinnut · #19 06-25-2011, 10:30 AM

Useless info:

The KT family of tubes were British-designed "Kinkless Transition" versions of the usual beam power tubes and pentodes - 6L6GC, EL34, and 6550. The KT66, KT77, and KT88's were all supposed to be improved versions of their respective tube.

Chris

JGR · #20 06-25-2011, 10:49 AM

Quote:

Originally Posted by rickdog

It sound to me like the answer is really "maybe" and "it depends." An amp designed for KT88s could have too high a plate voltage for 6550s. An amp designed for 6550s might strain to provide enough current for KT88s.

All things considered, I would expect it to be safer to substitute KT88s for 6550s. Run the amp under load and check for transformers overheating, you should be able to notice this before it would do any damage. Going the other way and putting too much voltage on 6550s seems like it would be more likely to cause a sudden, catastrophic failure that would cause expensive damage.

It's the screen voltage, not the plate voltage you need to watch. KT88s are rated for 600, 6550s for 450.