Freo-1
Well-Known Member
While chatting with my local amp tech the other day, we were discussing tubes, tube rolling, amp projects, etc. We both more or less came to the same conclusion:
While most of the current production output tubes are pretty reasonable, the big power tubes (KT88/6550) types do not have the same track record for success. None of them sound as good as NOS types (Tung-Sol, Sylvania, GE). Most are not very reliable over a period of time, and even the ones that are still do not last like the NOS types. The SED 6550C is the closest in longevity, but it just does not seem to have the same smooth sound character as NOS types.
KT88 types is even more bleak. Many of the KT88 types made do not even sound as good as the 6550, and reliability is suspect. The guitar players seem to like the JJ KT88 (it is rugged), but it just does not sound all that hot in audio applications. There have been complaints about pin size and soldering with the JJ as well.
Here is some background information on the Fender 400PS, which goes into some explanation "why you should use the expensive GE 6550A tubes".
Quote
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.
Here are the GE-6550A data sheets for you to see if the other so called 6550's measure up to the high performance GE-6550A standard.
High performance with long service life is the hallmark of the GE-6550A.
Quote
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?
While most of the current production output tubes are pretty reasonable, the big power tubes (KT88/6550) types do not have the same track record for success. None of them sound as good as NOS types (Tung-Sol, Sylvania, GE). Most are not very reliable over a period of time, and even the ones that are still do not last like the NOS types. The SED 6550C is the closest in longevity, but it just does not seem to have the same smooth sound character as NOS types.
KT88 types is even more bleak. Many of the KT88 types made do not even sound as good as the 6550, and reliability is suspect. The guitar players seem to like the JJ KT88 (it is rugged), but it just does not sound all that hot in audio applications. There have been complaints about pin size and soldering with the JJ as well.
Here is some background information on the Fender 400PS, which goes into some explanation "why you should use the expensive GE 6550A tubes".
Quote
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.
Here are the GE-6550A data sheets for you to see if the other so called 6550's measure up to the high performance GE-6550A standard.
High performance with long service life is the hallmark of the GE-6550A.
Quote
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?
