• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Vote for your favorite 6550/KT88

Freo-1

Freo-1

Well-Known Member
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."
 
Register to hide this ad
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.
 
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:
 
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
 
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 O said:
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.
Click to expand...

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
 
Freo-1 said:
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
Click to expand...

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.
 
Freo-1 said:
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."
Click to expand...
Tung-Sol USA first plated insides with gold then carbonized over the gold I have 6 ea 6550 3225904 the magic is very special this one is very powerful.
 
Last edited:
fxer1982 said:
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.
Click to expand...
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. :(
 
Haven't had a problem with any of them and they all sound good to me, enough so that if I hadn't tried anything else, I'd be happy with whatever I was using. To me, a good tube compared to a good tube, the difference is that last 5 or 10% and even that is preference / equipment related. That being said, I picked up two quads of the real Svetlana 6550C =C= some time ago and they are my current favorites. I've tried just about all the current issue 6550 / KT88 out there except Mullard or anything from China. Next favs are the Tung-Sols followed by EHX 6550. The GL KT88s were OK, but didn't wow me. I don't think I'd spring for the premium price over the other made in the same factory offerings.
 
Mr Boochie said:
Sadly, NOS or good used 25-year-old tubes are getting hard to find.

If I were to get a modern tube amp, I'd prolly stick to EL84, EL34, or 6L6GC. Just to keep the unit viable for the next ten years or more.
Click to expand...
My Tung-Sol 6550 date 3225904 so they are 65 years old..Phil Said now your amps are good for another 50 years. im 72 years old can't take them with me...

I was lucky ebay had a AP-437 in Original box I won the auction. Then two days later another AP-437 in original box was listed from the same ohio cold storage building. Who ever placed them on ebay were not the new owners of the storage building we chatted on ebay told me he never knew the amps were in the building behind other boxes. I won that one too. When I got them to my home I opened them up to find completely with all original tubes never been energized except for then factory set up burn in after biasing do not know if they did any burn in on the amps before assembling into the largest console they made only two variations of the large cabinets for the home. In 1961 it was sold near 5500.00 in today dollars that would be much more near 45,000.00 for the largest consoles each stereo so two mono blocks per console...two turn tables, a stereo tape deck, stereo pre amp, tuner, speakers.. the catalog never said how much they weight yet they show them and are taller than the lady's next to them. So I got them home and along with my photos I ask what to do with them before powering them up, I found a tech near me here and he didn't do much but scratch them and replace a couple of caps...if you go to youtube and look up " Phils Analog Basement " then Stromberg Carlson AP-437 he went through them and replaced all that needed to be and also a limiter to not blast the circuit and tube with to much power on start up...all the tubes were not perfect but plenty of life and here at home sound just beautiful, I can here the horse hairs on cellos, if I play Metallica its like your on Stage surrounded by them. Pink Floyd again like your on stage with them.
the tube arrangement Is 7025, BH7a, mullard GZ34, P/P tung-sol 6550 3225904 black plate no holes 3 D shaped getters big beautiful music out of them. 40 watts normal 100 watts instantaneous. even at a low volume with them running at full power with 3 on the pre amp WOW thunderous bass creamy mids and crispt high end freq not harsh...Im very Honored to have them and the Tech Phil is a perfectionist and he has great integrity to his workmanship. So thats how I got the 6550's dated 3225904 I have a total of 6 tubes three amps. Only two amps are ready to work the third I bought yrs ago and had that gone through at that time, some 15 years later I found the two out of Ohio.... I have three techs over to my house to listen and each had said they are McIntosh killers for Fact.... One was a McIntosh trained for 25 years who worked at Clark Music Syracuse, New York
Now for a couple of hrs of music..
 
Last edited:
fxer1982 said:
My Tung-Sol 6550 date 3225904 so they are 65 years old..Phil Said now your amps are good for another 50 years. im 72 years old can't take them with me...

I was lucky ebay had a AP-437 in Original box I won the auction. Then two days later another AP-437 in original box was listed from the same ohio cold storage building. Who ever placed them on ebay were not the new owners of the storage building we chatted on ebay told me he never knew the amps were in the building behind other boxes. I won that one too. When I got them to my home I opened them up to find completely with all original tubes never been energized except for then factory set up burn in after biasing do not know if they did any burn in on the amps before assembling into the largest console they made only two variations of the large cabinets for the home. In 1961 it was sold near 5500.00 in today dollars that would be much more near 45,000.00 for the largest consoles each stereo so two mono blocks per console...two turn tables, a stereo tape deck, stereo pre amp, tuner, speakers.. the catalog never said how much they weight yet they show them and are taller than the lady's next to them. So I got them home and along with my photos I ask what to do with them before powering them up, I found a tech near me here and he didn't do much but scratch them and replace a couple of caps...if you go to youtube and look up " Phils Analog Basement " then Stromberg Carlson AP-437 he went through them and replaced all that needed to be and also a limiter to not blast the circuit and tube with to much power on start up...all the tubes were not perfect but plenty of life and here at home sound just beautiful, I can here the horse hairs on cellos, if I play Metallica its like your on Stage surrounded by them. Pink Floyd again like your on stage with them.
the tube arrangement Is 7025, BH7a, mullard GZ34, P/P tung-sol 6550 3225904 black plate no holes 3 D shaped getters big beautiful music out of them. 40 watts normal 100 watts instantaneous. even at a low volume with them running at full power with 3 on the pre amp WOW thunderous bass creamy mids and crispt high end freq not harsh...Im very Honored to have them and the Tech Phil is a perfectionist and he has great integrity to his workmanship. So thats how I got the 6550's dated 3225904 I have a total of 6 tubes three amps. Only two amps are ready to work the third I bought yrs ago and had that gone through at that time, some 15 years later I found the two out of Ohio.... I have three techs over to my house to listen and each had said they are McIntosh killers for Fact.... One was a McIntosh trained for 25 years who worked at Clark Music Syracuse, New York
Now for a couple of hrs of music..
Click to expand...
This is how I feel about most of the amps I work on. You want the whole world to hear them, but then your neighbor mentions they could hear the windows vibrating yesterday and is everything okay.
 
albusark said:
This is how I feel about most of the amps I work on. You want the whole world to hear them, but then your neighbor mentions they could hear the windows vibrating yesterday and is everything okay.
Click to expand...
That,s the funny thing I've never had to increase the volume it is set at 3 on the pre amp. yet it is so robust even at a low volume. the amp must be at full out put before all freq are flat at a level across the spectrum so I use my pre amp for volume and run the mono blocks at full power at a low volume It just magic voicing at a high power I've never tried to push that. I'd rather not burn up my voice coils even though they are rated at 10-100 watts on the Altec woofers. My computer has a DAC card also has EQ has the music player with mixer volumes, output to preamp volume, then preamp to mono blocks. So Im giving low volume into mixer low volume into preamp, high power out to speakers. its a cleaner way for recording the band years ago. So that's the way I have it set up now.
 
Last edited:
Original Winged C (not reissue) for both.
For reissue, GL KT88 and TungSol 6550, though not up to the originals. The EH KT88 is pretty decent, as well.
 
albusark said:
This is how I feel about most of the amps I work on. You want the whole world to hear them, but then your neighbor mentions they could hear the windows vibrating yesterday and is everything okay.
Click to expand...

My neighbour across the road once thought my old band was having a reunion at my place the night before. It was actually just a trip down memory lane listening to a reel-to-reel of one of our shows from long ago...apparently it was his windows that were rattling:biggrin:
 
The NOS tubes may sound better but are getting tougher and tougher to find. If a person has an amp that is pretty rough on power tubes then sort of becomes a moot point.
Finding a matched quad of NOS may be doable, but not too likely to find a matched octet or higher number of tubes.
 
Watching a youtube video by the Elpaso TubeAmps guy a few weeks ago who said Telefunken is buying tubes from JJ. Of course they have to met Telefunken standards. Common practice in the days when tubes ruled. Manufacturers buying from each other putting their brand on the tubes.

A few years ago in a build using the 12AT7 tubes I tried multiple new offerings and found a big difference in output in the two triodes inside the tubes. Bought some NOS ones and the tolerances were much closer.
 
You must log in or register to reply here.
Back
Top Bottom