Vote for your favorite 6550/KT88

[Freo-1]

OK, OK, I know this is a bit like herding cats, but, what are your favorite 6550/KT88 tubes?

Back in 2004, Vacuum Tube Valley ranked their thoughts as follows:

Genalex KT88 Gold Lion 1969 - 4.87

Tung-Sol 6550 1963 Solid Grey Plate - 4.77
JJ KT88 2002 - 4.63
Ei KT90 1999 - 4.52
EH KT88 Reflektor 2002 - 4.16
Sveltana 6550 2001 - 4.13
Svetlana SVKT88 2002 - 4.09
Svetlana SV6550C Reflektor 2002 - 3.98
Philips Sylvania 1970s - 3.98
Chinese 6550 Valve Art 2002 - 3.89
GE 6550A 1970s - 3.78

Since then, there have been a couple of new KT88/6650 types released (the Tung Sol 6550 re-issue, and the Genalex KT88.

I will state up front that while I like the sound of the Genalex KT88 re-issue, I've had nothing but trouble with reliability. As a result, my ranking of that tube is downgraded accordingly.

So, based on my personal experience, here is my ranking of the tubes (I'm judging on sound AND reliability). Disclaimer: I did not take the MO KT88 into account (too rare)

1. Tung Sol 6550 Black Plates (nuff said)
2. Tung Sol 6550 Gray Plates
3. GE 6550A welded plate
4. Tie: Sylvania 6550/GE 6550A stapled plate
5. Tie: SED 6550C/JJ KT88/SV 6550C
6. Gold Lion Re-Issue (good sound/suspect reliability)
7. SED KT88
8. Chinese KT88

I did not rank anything else, because I've not had personal experience with them. Certainly, the EH KT88 deserves some consideration. There is a noticeable drop off in sonics between the Tung Sol, and everything else, and a more significant drop after the US NOS tubes. (IMHO) YMMV

Lastly, I'm posting this information about the 6550. For those who think the Russian/Chinese tubes are just as good, read the following from the website dedicated to the Fender 400PS:

"Q: Are all 6550's the same?
No, for the following reasons.

With the way tubes are being made in other countries today, there is little chance of any of the same type of tubes ever being made the same from one country to another.

There are no unifying standards behind what they produce with respect to standards that cover their manufacturing methods, material standards, or operational electrical performance characteristics.

In the USA we had government specifications, with industry's material standards and testing practice for the vacuum tube, and an electronics industry's standard to follow. Not all tube companies were qualified to supply specific vacuum tube products to the government of the USA.

The rest of the world's tube companies *individually* brand what ever they think their tube is, for THEIR standard for a tube type. This most often is different country to country, and can change from production run to production run.

This is why we have the problems with same type vacuum tube performance being all over the map from off shore today.

For example, if they can't even make a tube with the right size pins for our USA tube sockets, would you expect them to have the correct electrical characteristics dead-on spec for a Sylvania or GE of the same branded type of tube?

Picture

These over sized base pins were broken off by a customer who could not get this tube in the socket of his Fender Twin Reverb. These tubes should have never been sold in the US market place.

If USA industry standards were on the minds of those who make the vacuum tubes from off shore, I would not have had to re-base these tubes to fit the sockets made in the USA, and you would not have these pictures to look at on this FAQ page."

 

[Freo-1]

More supporting data for NOS tubes:

Why do I have to use those high priced GE-6550A's?

You don't HAVE to do anything.
But, when you do the proper thing, it's a nice thing.
Then... everything works as it should.

It's like anything else, when specific things are designed to work together to yield the "maximum" in performance with long service life. This is the case with the 400-PS with the original Tungsol 6550, as well as with the even higher performance GE-6550A.

Likewise, the high performance Musicman amps were specifically designed to run the Sylvania 6CA7 tube, because of their well known superior performance and service life.

In both cases, no other tubes were considered for use in these amps. Not even as a substitute replacement tube.

A year or so back I had a 400-PS owner stop in with a set of NEW Russian 6550WE tubes to be installed. I really had to play games with that 400 to get those tubes to run. This was their best day right out of the box for these tubes, and the best they could do was 124 watts per load at 100 Hz for a 372 watt total output from a conservatively 435 watt rated amp.

After 72 hours of hard dynamic signal running time and a re-adjustment, that 372 watt total figure dropped by almost 50 watts.

It's one thing to print the specs for a tube, and quite another to make the tubes that live up to those specs with LONG continued service life.

 

[zekk]

Re-issue Gold Lion KT-66.

After reading so much praises about this re-issue Gold Lion KT-66 in the Asylum Forum, I bought a quad of them and was disappointed.

Plugged into my MC-30, after 20 mins. of playing, it started to produce periodical popping sound. I than revert back to the RCA 6L6 GC, and everything is fine again.

Nevertheless, no stress but $170.00 ......:sigh:

 

[FalconEddy]

I always liked the sound of the Tung-Sol 6550 gray plates.

I used to have a pair of 147 Leslies that I used on stage with my B3, and they each took a pair of them. Back then, you could get a mid-'60's production new pair for $35-$40.

They also lasted much longer than the GE and Sylvania 6550A's, which were a bit less money.

When you're making the plates glow orange-red five to six times a week for two to three hours at a time, it was worth it to have tubes that had a longer lifespan.

. . Falcon

 

[Steve O]

My experience with vintage HiFi amps (primarily MC275/MC60 & MK3):

1. Real GEC KT88. Probably best balanced of the 6550/KT88 types. Since I've got some of them I'll include them. Long lasting.

2. Real Tungsol 6550. I can't really tell much difference betw black plate, no holes grey plate, holes, top getters, side getters, blah blah blah so I use em all indiscrimately. Similar to GEC KT88. Long lasting.

3. GE 6550A. Not quite as refined as GEC and TS but still quite likeable. These are the crimped plate variety...only have a pair of tired old welded plates about the home.

4. Real Svetlana 6550B3 (pill getters). Nice sound but less refined than GEC or TS and not as robust sounding as GE. Not common. Not as long lived as GEC, TS or GE. Need 24-48 hr burn in for bias stability.

5. Real Svetlana 6550C. Similar to B3 and maybe interchangable ranking with it. Easy to find. Stable.

On deck: Reissue GL KT88, Reissue TS 6550.

 

[Freo-1]

My experience with vintage HiFi amps (primarily MC275/MC60 & MK3):

1. Real GEC KT88. Probably best balanced of the 6550/KT88 types. Since I've got some of them I'll include them. Long lasting.

2. Real Tungsol 6550. I can't really tell much difference betw black plate, no holes grey plate, holes, top getters, side getters, blah blah blah so I use em all indiscrimately. Similar to GEC KT88. Long lasting.

3. GE 6550A. Not quite as refined as GEC and TS but still quite likeable. These are the crimped plate variety...only have a pair of tired old welded plates about the home.

4. Real Svetlana 6550B3 (pill getters). Nice sound but less refined than GEC or TS and not as robust sounding as GE. Not common. Not as long lived as GEC, TS or GE. Need 24-48 hr burn in for bias stability.

5. Real Svetlana 6550C. Similar to B3 and maybe interchangable ranking with it. Easy to find. Stable.

On deck: Reissue GL KT88, Reissue TS 6550.

Steve, how much of a difference do you notice between the MO KT88 and the TS 6550? Would you say it is a significant or minor difference?

People say that the TS Black Plate lasts longer than the gray plate. What's your experience with this?

Lastly, be very careful with the KT88 re-issue. For the reasons posted above, there is no reliable method to ascertain tube performance as it breaks in. Better keep some extra resistors on hand, just in case

 

[Steve O]

Steve, how much of a difference do you notice between the MO KT88 and the TS 6550? Would you say it is a significant or minor difference?

People say that the TS Black Plate lasts longer than the gray plate. What's your experience with this?

Lastly, be very careful with the KT88 re-issue. For the reasons posted above, there is no reliable method to ascertain tube performance as it breaks in. Better keep some extra resistors on hand, just in case

To my ears and on the limited range of equip I've used them in, the diff betw GEC KT88 and TS 6550 isn't too great. IOW, from what I've heard, I wouldn't go out of my way or spend big $$ for the KT88s if I had access to the TS 6550s (and vice versa). But the 88s ARE marginally better all else equal.

As to TS life, I can't really comment since I've used them indiscriminately. Also, they've tended to spend their time in Mac unity coupled amps which are pretty easy on them. Actually, I've never worn one out in a Mac amp. Same for GEC KT88, thus my comments on long life. I think GE 6550A is also long lived but had one let go in my 275 a while back so less sure here but they do well in my MK3s. FWIW, any of these three are definitely longer lived than current mfg 6550. I can almost see the getter disappear on the 6550Cs. Curiously, getter seems to appear on the B3s.

I appreciate the heads-up regarding the GL Reissue KT88. Unfortunately, I just purchased a couple of sextets to retube a CJ Premier One I just acquired. This thing seems to treat output tubes a bit harshly so I'm kinda wary of the reissue KT88s as of now. Fortunately, the CJ fuses the B+ lines to each channel so if issues arise, damage will be limited. Each output tube is individually biased too. I hope the reissues work out cause they weren't cheap and until recently were well reviewed.

 

[fxer1982]

My 6ea 6550 Tung-Sol black plate no holes 3 getters 3225904 made in the USA

 

[fxer1982]

OK, OK, I know this is a bit like herding cats, but, what are your favorite 6550/KT88 tubes?

Back in 2004, Vacuum Tube Valley ranked their thoughts as follows:

Genalex KT88 Gold Lion 1969 - 4.87

Tung-Sol 6550 1963 Solid Grey Plate - 4.77
JJ KT88 2002 - 4.63
Ei KT90 1999 - 4.52
EH KT88 Reflektor 2002 - 4.16
Sveltana 6550 2001 - 4.13
Svetlana SVKT88 2002 - 4.09
Svetlana SV6550C Reflektor 2002 - 3.98
Philips Sylvania 1970s - 3.98
Chinese 6550 Valve Art 2002 - 3.89
GE 6550A 1970s - 3.78

Since then, there have been a couple of new KT88/6650 types released (the Tung Sol 6550 re-issue, and the Genalex KT88.

I will state up front that while I like the sound of the Genalex KT88 re-issue, I've had nothing but trouble with reliability. As a result, my ranking of that tube is downgraded accordingly.

So, based on my personal experience, here is my ranking of the tubes (I'm judging on sound AND reliability). Disclaimer: I did not take the MO KT88 into account (too rare)

1. Tung Sol 6550 Black Plates (nuff said)
2. Tung Sol 6550 Gray Plates
3. GE 6550A welded plate
4. Tie: Sylvania 6550/GE 6550A stapled plate
5. Tie: SED 6550C/JJ KT88/SV 6550C
6. Gold Lion Re-Issue (good sound/suspect reliability)
7. SED KT88
8. Chinese KT88

I did not rank anything else, because I've not had personal experience with them. Certainly, the EH KT88 deserves some consideration. There is a noticeable drop off in sonics between the Tung Sol, and everything else, and a more significant drop after the US NOS tubes. (IMHO) YMMV

Lastly, I'm posting this information about the 6550. For those who think the Russian/Chinese tubes are just as good, read the following from the website dedicated to the Fender 400PS:

"Q: Are all 6550's the same?
No, for the following reasons.

With the way tubes are being made in other countries today, there is little chance of any of the same type of tubes ever being made the same from one country to another.

There are no unifying standards behind what they produce with respect to standards that cover their manufacturing methods, material standards, or operational electrical performance characteristics.

In the USA we had government specifications, with industry's material standards and testing practice for the vacuum tube, and an electronics industry's standard to follow. Not all tube companies were qualified to supply specific vacuum tube products to the government of the USA.

The rest of the world's tube companies *individually* brand what ever they think their tube is, for THEIR standard for a tube type. This most often is different country to country, and can change from production run to production run.

This is why we have the problems with same type vacuum tube performance being all over the map from off shore today.

For example, if they can't even make a tube with the right size pins for our USA tube sockets, would you expect them to have the correct electrical characteristics dead-on spec for a Sylvania or GE of the same branded type of tube?

Picture

These over sized base pins were broken off by a customer who could not get this tube in the socket of his Fender Twin Reverb. These tubes should have never been sold in the US market place.

If USA industry standards were on the minds of those who make the vacuum tubes from off shore, I would not have had to re-base these tubes to fit the sockets made in the USA, and you would not have these pictures to look at on this FAQ page."

Tung-Sol USA first plated insides with gold the carbonized over the gold i have 6 ea 6550 3225904 the magic is very special this one is very powerful.

 

[Mr Boochie]

Tung-Sol USA first plated insides with gold the carbonized over the gold i have 6 ea 6550 3225904 the magic is very special this one is very powerful.

The ones with alignment holes in the plates may be less likely to go ballistic on you.

I haven't heard a good Tung-Sol (USA) 6550 in years. Even real NOS St. Petersburg made Svetlana 6550C (=C=) is getting hard to find.

Both were excellent output tubes. Sadly, those manufacturing days are long gone.