KT120 tubes

[vintage_tube]

Originally Posted by nsgarch

And of course there's the issue of sonics. There aren't a lot of KT120's to choose from (sic!) and the KT120 tube box shown on the Upscale Audio's website is marked 9000 Gm, -- not an impressive transconductance rating when you consider there are both new and vintage KT88's that top 110,000

Hi Neal,

I believe you either met 10,000 or 11,000 vice 111K.

I do agree with you on the KT120's. Anyway, 9K for the most part, beats the average GL Reissue numbers of late that many have tried and like.

Bob

[Tonepub]

Originally Posted by nsgarch

Not just the tubes. Many circuit components have to be beefed up; especially bigger power transformers!

Listen to Ron Cornelius. And take Mr. DEALer's advice with a grain of salt Amplifiers are designed to perform optimally with a certain power tube, although sometimes one or two others can be made to work, usually by tweaking the bias adjustment, but then the amp isn't operating optimally though some might prefer the sound of the alternate tubes -- anyway, there is no bias adjustment on Mac amps. Back in the day when the 6550 was the most powerful output tube, many amps designed around the 6550 would not work very well with the newly developed KT88. The first people to run into trouble were the guitar players

And of course there's the issue of sonics. There aren't a lot of KT120's to choose from (sic!) and the KT120 tube box shown on the Upscale Audio's website is marked 9000 Gm, -- not an impressive transconductance rating when you consider there are both new and vintage KT88's that top 110,000 -- I'll bet the KT120's are perfect for ARC people, who like their sonics, and their Martinis, very dry!

It's pretty obvious you haven't heard any current ARC product. That may have been the house sound late 90's, but not any longer.

Investigating with a number of mfrs, it does seem to be a case by case situation and the designers I've talked to already (ARC, CJ, Prima Luna and Octave) have all said that to take maximum advantage of the tube, a redesign would be in order.

However, the question was, how do they sound? If you're relying strictly on numbers to determine how anything sounds, that's kind of silly. That's why I bought a couple of quads, to actually investigate.

[cmalak]

Jeff...I totally agree. I would not call the current ARC amplifier line-up as "dry." In fact I think they are tonally very dense.

On the KT120 tubes, I just called ARC and they are shipping the current line up of amps (VSi60 integrated, the VS115 stereo power amp, and all the Reference line power amps - 110/210/610) with the KT120 tubes. In the ARC designs, they are a straight drop-in replacement for the 6550s. No circuit or transformer redesign needed to accomodate the new tube. They have not changed the bias on any of the designs so the KT120s will pull the same current as the 6550s before them, so in essence they will be run more conservatively than the 6550s. That will translate into longer tube life and with less tube failure rates.

In my situation the tube swap on the REF 110 will take the power output from 110wpc to 130wpc. They seem to think that the KT120s add bass weight, punch and articulation, providing a better foundation to the music, as well as a wider dynamic presentation to the music, as compared to the 6550s. I hope this helps.

[nsgarch]

Originally Posted by tonepub

It's pretty obvious you haven't heard any current ARC product. That may have been the house sound late 90's, but not any longer.

It was a joke. Relax!

Investigating with a number of mfrs, it does seem to be a case by case situation and the designers I've talked to already (ARC, CJ, Prima Luna and Octave) have all said that to take maximum advantage of the tube, a redesign would be in order.

An obvious conclusion, no?

However, the question was, how do they sound? If you're relying strictly on numbers to determine how anything sounds, that's kind of silly. That's why I bought a couple of quads, to actually investigate.

So what amp will you use for your evaluation? And how do you make it apples to apples -- meaning if you use an amp designed around the KT120 tube (if one exists yet) then KT88/6550's probably wouldn't get a fair shake, assuming they could be safely used in a KT120-based amp. Conversely, if one (dares to) try the KT120's in an amp designed around KT88's, 6550's or even EL34's, then the KT120's won't really get a chance to shine.

Which brings us to the fact that many people who prefer tubes generally, often wind up with a preference just for amps that utilize one of the major power tubes such as EL34's, 6550's, etc. I think that's where the real preferences occur among tube amp lovers. So it's going to take time, and the appearance of other KT120 offerings, before a clear KT120 identity or sonic profile can emerge.

In the meantime, if you are someone who, for instance doesn't care for the sound of KT88's, you're likely to describe the KT120 as "just a KT88 on steroids" , whereas if one likes KT88's, and wished only for a bit more power so they could (also) get good bass performance out of a full range speaker, then a KT120-based amp might be just the ticket! The Shuggie KT88Z is just an amazing sounding KT88 in my opinion. If the KT120 achieves the same sonics but with more power, that would be a real treat!

I wonder what NOS KT120's sound like compared to the new Russian ones?

[nsgarch]

Originally Posted by vintage_tube

Hi Neal,

I believe you either met 10,000 or 11,000 vice 111K.

I do agree with you on the KT120's. Anyway, 9K for the most part, beats the average GL Reissue numbers of late that many have tried and like.

Bob

Yeah, I got carried away Bob! I guess we're all hoping for a few more zeros these days

[Tonepub]

Originally Posted by nsgarch

It was a joke. Relax!

An obvious conclusion, no?

So what amp will you use for your evaluation? And how do you make it apples to apples -- meaning if you use an amp designed around the KT120 tube (if one exists yet) then KT88/6550's probably wouldn't get a fair shake, assuming they could be safely used in a KT120-based amp. Conversely, if one (dares to) try the KT120's in an amp designed around KT88's, 6550's or even EL34's, then the KT120's won't really get a chance to shine.

Which brings us to the fact that many people who prefer tubes generally, often wind up with a preference just for amps that utilize one of the major power tubes such as EL34's, 6550's, etc. I think that's where the real preferences occur among tube amp lovers. So it's going to take time, and the appearance of other KT120 offerings, before a clear KT120 identity or sonic profile can emerge.

In the meantime, if you are someone who, for instance doesn't care for the sound of KT88's, you're likely to describe the KT120 as "just a KT88 on steroids" , whereas if one likes KT88's, and wished only for a bit more power so they could (also) get good bass performance out of a full range speaker, then a KT120-based amp might be just the ticket! The Shuggie KT88Z is just an amazing sounding KT88 in my opinion. If the KT120 achieves the same sonics but with more power, that would be a real treat!

I wonder what NOS KT120's sound like compared to the new Russian ones?

So, what's the point you are trying to make?

[vintage_tube]

Originally Posted by cmalak

Jeff...I totally agree. I would not call the current ARC amplifier line-up as "dry." In fact I think they are tonally very dense.

On the KT120 tubes, I just called ARC and they are shipping the current line up of amps (VSi60 integrated, the VS115 stereo power amp, and all the Reference line power amps - 110/210/610) with the KT120 tubes. In the ARC designs, they are a straight drop-in replacement for the 6550s. No circuit or transformer redesign needed to accomodate the new tube. They have not changed the bias on any of the designs so the KT120s will pull the same current as the 6550s before them, so in essence they will be run more conservatively than the 6550s. That will translate into longer tube life and with less tube failure rates.

In my situation the tube swap on the REF 110 will take the power output from 110wpc to 130wpc. They seem to think that the KT120s add bass weight, punch and articulation, providing a better foundation to the music, as well as a wider dynamic presentation to the music, as compared to the 6550s. I hope this helps.

I received just a slightly different answer -- for the most part it reiterated what you posted. Anyway, here's what I was told:

Just out of curosity more than anything else, spoke to ARC tech support and they are now installing the KT120's in their newer amps as of the 3d (or 3d week) of November. They believe the KT120 tube has better foundation, more weight, bass and more authority than the 6550's (may have been the same guy I spoke with...dunno).

However, regarding their legacy amps, they have not yet tested them in those and to be on the safe side, recommend no one try as yet until they have a better idea on the range of biasing on the legacy amps, etc.

They will eventually evaluate the KT120's in the legacy products and will post their findings on their web site. As a side note, of course, the KT120 will not fit some of those legacy amps.

Bob

[cmalak]

Bob...I didn't ask about their legacy amps. The guy I talked to said they are shipping the KT120s in their current amp line up (as I listed above). Sounds like we may have talked to the same person. Thanks for clarifying for those who own legacy amps.