Power tubes?? Who, What, When Where how??

[steelhorse]

Hey Marty since the 6550 and the KT88's are essentially the same tube )I realize the KT=kinkless triode) why are they considered as different tonally as they are?

They're not even separated as being part of the same family but different but they are considered one in the same by many dealers.

 

[MartyStrat54]

Hey Marty since the 6550 and the KT88's are essentially the same tube )I realize the KT=kinkless triode) why are they considered as different tonally as they are?

They're not even separated as being part of the same family but different but they are considered one in the same by many dealers.

In an effort not to cause confusion, I am changing things a bit here. The KT (Kinkless Tetrode) are also called beam power tetrode. How these parts operate under a normal load is how they get their name. In a KT tube, the operating curve is smooth, with no "kinks" in it. Some beam power tubes will get a kink in the flow of their electrons when they are operating near max output levels. Think of it as bending a water hose that is on. You put a "kink" in the hose and it restricts the flow of the water. In the very early development stages, M-O-V could not get the design to work. They had a sharing agreement with RCA. RCA was able to get the design to work. This tube became the 6L6. M-O-V came out with the KT66 in 1936 (so the 6L6 is older). This is were the "tree" starts and apparently there is a connection between a 6550 and a KT88, just as there is between a KT66 and a 6L6. They are all beam tetrode power tubes. 6CA7/EL34's are power pentodes and are of differing construction.

Although a 6550 is "in" with nu metal and other metal music, the fact is, the KT88 has less distortion and breakup than a 6550. That is why a KT88 is desirable for use in Hi Fi amps. A KT88 push-pull pair in class AB1 fixed bias is capable of 100 watts of output with 2.5% total harmonic distortion or up to about 50W at low distortion in hi-fi applications. The 6550 supposedly can put out 100 watts per pair, but the THD is much higher.

As I said the 6550 is a big 6L6, the KT88 was derived from a transmitting tube that could handle 1250 volts on the plate. The KT88 is the big bad ass, but of course there were bigger models that are no longer in production, such as the KT90 and the KT100. I have heard that a Chinese tube maker is trying to recreate these tube.

The KT88 was designed purely for an audio application. The 6550 was designed to operate power servo's. They both have clean sounds, but the KT88 is cleaner. The KT88 can take 800 on the plates and the 6550 is rated at 600. Either one of these tubes can handle the higher plate output of say a Super Lead without fear of a melt down. Tone wise I will pick a KT88 and I would love to have a 50 watt 800 with a pair of them. Of course, my KT88's would have to be real ones.

In closing, the break up of these tubes is much different. The 6550 will break up faster than a KT88. This by itself creates a difference in the tubes and how they sound. From a pure audio aspect, the KT88 is a more musical sounding tube. However, it is hard to get natural breakup from a KT88. You would need a distortion pedal, because even if you dimed the amp with KT88's, it would still be pretty clean sounding. Loud as hell, but clean.

I wanted to add that new production KT88's such as JJ's do not exhibit the same tone and distortion characteristics as an NOS KT88. A new JJ KT88 for instances will not handle the same plate voltage and will break up earlier when driven hard. The same holds true for current production 6550's. My above remarks were made based on NOS tubes. Current production 6550's and KT88's could be similar in construction and sound. This is because a lot of tube manufacturers use the same internal parts for different tubes. I haven't been able to compare "new" 6550's with "new" KT88's. There might not be much difference, because they could very well be the same, or almost the same tube. Maybe in the future they will call them KT6550's and KT6L6's.

 

[steelhorse]

Unless you get a 2203KK

Thanks for the detailed but easy to understand explanation Marty, I knew I could count on you!

 

[steelhorse]

p.s. what would you consider to be 'real' KT88's?

 

[MartyStrat54]

Unless you get a 2203KK

Thanks for the detailed but easy to understand explanation Marty, I knew I could count on you!

Doesn't the KK use the famous clipping diodes?

 

[MartyStrat54]

p.s. what would you consider to be 'real' KT88's?

M-O-V, or MO Valve, or real Genalex Gold Lions. They were made from 1956 until 1988. A quad of real Gold Lion KT88's run about $150 to $200 for each tube, or $800 for a quad. Still interested?

 

[steelhorse]

M-O-V, or MO Valve, or real Genalex Gold Lions. They were made from 1956 until 1988. A quad of real Gold Lion KT88's run about $150 to $200 for each tube, or $800 for a quad. Still interested?

Not really. I'm certain I can get great tone out of the stock tubes and improve them with JJ's later.

 

[MartyStrat54]

Not really. I'm certain I can get great tone out of the stock tubes and improve them with JJ's later.

Well I was sorta joking as that is to rich for even me. I think Viking has his amp sounding really sweet with new production tubes. It can be done. The main thing to remember is that you are not going to get 200 watts out of four KT88's in an 800. First off, you are limited by the power supply. So the tubes are basically gonna run in the 25 watt a piece range. You have to have power to make power. However, running a tube under its rating means that you should get great tube life.

 

[Jae]

Nice Matched Pair of Mullard xf2 DBL Halo EL34 Tubes - eBay (item 350247622709 end time Sep-11-09 18:31:18 PDT)

I'm doing you a favor. Hurry before I buy them.

Hey all. Thanks for all these great posts. I find them very informative and I'm learning about different tubes besides the El34s. Keep it coming!

BTW, Marty, I asked the guy if he ships to Canada. His reply:

"That's correct. I don't ship to Canada."
I hope he doesn't have anything against Canadians (lol).

So I guess you better buy them, or you probably already have what you like anyways.

 

[MartyStrat54]

Just curious. Is there anyone using Sylvania "FAT BOY" 6L6GC's in their amps? This is to include the original, the STR387 and the STR415. These are some bad ass 6L6's and I would like to hear from anyone that uses them on how they sound and their reliability.

Also, there was an STR416. This was an EL34 used mainly in Boogies back in the early 80's, like a Mark II. Anyone have any of these?

If you run NOS 6L6's or EL34's, please post and let us know what you are running.

 

[Jae]

Just curious. Is there anyone using Sylvania "FAT BOY" 6L6GC's in their amps? This is to include the original, the STR387 and the STR415. These are some bad ass 6L6's and I would like to hear from anyone that uses them on how they sound and their reliability.

Also, there was an STR416. This was an EL34 used mainly in Boogies back in the early 80's, like a Mark II. Anyone have any of these?

If you run NOS 6L6's or EL34's, please post and let us know what you are running.

I recently got a quad Sylvania Fat boy 6CA7s, but they are probably not the same ones you are talking about, or are they? If I remember correctly or maybe not, I heard they are essentially 6L6s?

The quad is coming in on Tuesday I'm guessing. Can't wait to get them put in.
BTW, if there is anyone here familiar with tube biasing please tell me what you know. Is it better to bias them yourself or in fact get an amp tech to do it at a price. I mean, is it risky doing it yourself if you don't have a clue about biasing a tube, but want to jump in an do it? (That's me). I've heard of people biasing and doing it themselves, but I never got around to actually doing it. I think if I had a chance I could save myself a few bucks.

Being able to do it myself would also allow me to throw in and experiment as many tubes I can without the extra fee. Or is it really that simple?

I have a couple of JMP Superleads and a '78 JMP Master, which I don't want to damage due to bad biasing.

Is it also dangerous to do?

Another question is.. What are some really good tube biasing kits or equipment ( i heard about Webers being good).

 

[Jae]

Hey Marty,

So I found out that at least one of the telefunkens I have is a smooth plate. I ended up getting a pair of ribbed plate Tele's and a separate smooth Tele.

I haven't compared the two side by side, but will do so when I get the chance. From the looks of it the smooth plate was the better one. Another guy told me this was a good one.

 

[Jae]

Sorry, the last post was psoted in the wrong section. Stupid me.

 

[MartyStrat54]

Hey, those 6CA7's are like EL34's, not 6L6's. A 6CA7 is an American sub for a British EL34.

 

[Jae]

Hey, those 6CA7's are like EL34's, not 6L6's. A 6CA7 is an American sub for a British EL34.

Oops. I may be wrong. I heard they are similar to another type of tube, not sure if it was EL34s. Something about not being pentodes, but beams. That's all I could muster up.

 

[Jesstaa]

Yo Marty, if I were to chuck some N.O.S KT66's in my amp, what kinda thing would I expect? I'm looking to experiment a little, and I definitely want some N.O.S tubes.

Also, what N.O.S KT66s kick the most ass?

 

[RiverRatt]

Can someone tell me when the St. Petersburg factory quit making EL34 tubes under the Svetlana brand? I have a set from around 1999 and was wondering if they are from the Xpo-pul factory or not.

My GTEL34M's are drifting way too much lately. I've rebiased them every week for the past month or so and they are always 4 or 5mV apart. I put in the Svets I was keeping for an emergency and they sound a lot better than I remembered.

I guess it's time to bite the bullet and pick up some RFT's.

 

[Lespaulnmarshall]

I Love the stock KT 66's in my Vintage Modern, And for a Plexi I like KT 88's ! The stock KT 66's in the VM are pretty good but maybe I'll change them for some Grove Tube KT 66's.

 

[MartyStrat54]

Yo Marty, if I were to chuck some N.O.S KT66's in my amp, what kinda thing would I expect? I'm looking to experiment a little, and I definitely want some N.O.S tubes.

Also, what N.O.S KT66s kick the most ass?

Well, a 6L6 and a KT66 are both beam power tubes. There is a lot of history that ties these two tubes together. With that being said, the sound of a KT66 is very similar to a 6L6. There are a lot of good NOS choices for 6L6 tubes at a reasonable price. However, NOS KT66's are much rarer (in the USA) and they are very expensive. Based on that, I would probably go with current production if I wanted to try KT66's..

I think if my amp had 6L6GC's in it, I would find myself some NOS 6L6's and go that route.

 

[Jae]

Ok. Today I ended up purchasing an exact matched NOS pair Mullard xf2 El34s with double Os.. They look immaculate.

I'm going to have them installed and biased tommorrow on my JMP '78 Masterlead 50W head. The tubes in there now are GT EL34's.

I'll let you all know how it goes.