KT150 v KT120 Tubes

Priaptor · Jun 5, 2014

Just got my KT150 tubes for my ARC REF75 and it was a plug and play install. No issues, at least day 1.

At this point I cannot comment on SQ as the tubes were right out of the box, all matched, but nothing broken in, so I am not in a position to comment other than to say, there is definitely more kick than with the KT120s-sounds like a much more powerful amp. Whether that turns out to be a good or bad thing we will see and refuse to judge at this time. Different isn't always better.

Curious if anyone else has made the plunge to these relatively new tubes and what your feelings are.

rbbert · Jun 5, 2014

I don't currently use a tube amp, but at T.H.E. Show Carl of NOLA had them in his Ref75 and said so far (after just over a month) he's not going back. The Primaluna Dialogue was also using the KT150 and sounding good with Amati Futuras; the exhibitor there said it has become their recommended power tube.

Priaptor · Jun 5, 2014

rbbert said:
I don't currently use a tube amp, but at T.H.E. Show Carl of NOLA had them in his Ref75 and said so far (after just over a month) he's not going back. The Primaluna Dialogue was also using the KT150 and sounding good with Amati Futuras; the exhibitor there said it has become their recommended power tube.

Yes that is why I have decided to try the KT150s. I own Carl's Concert Grands and have been using the REF75 based on his recommendation and he basically told me to "run" and get these tubes to replace the KT120s in the REF75. Sometimes the evil of good is better so am curious if others with KT120 tube amps have tried these. Like I said in the OP mine works just fine, just too early to evaluate based on my 1.5 hours of evaluation. I am currently running the amp to (break in the tubes) and will do some critical listening later.

The interesting thing about this crazy hobby of ours is that "break in" usually means an empty chair listens more than we do!

JackD201 · Jun 5, 2014

Are 150s drop in replacements for 120s or just in the Ref 75? I have a pair of KT120 monoblocks with autobias. Curious if I can swap tubes out.

Priaptor · Jun 5, 2014

JackD201 said:
Are 150s drop in replacements for 120s or just in the Ref 75? I have a pair of KT120 monoblocks with autobias. Curious if I can swap tubes out.

They were plug and play in my REF75 and I know others using them in other recent ARC gear. For me the bias was perfect. Didn't have to adjust a thing. I was surprised. The tech specs look like it should be compatible with all KT120.

Call the manufacturer of your amp. The cost of matched tubes were relatively reasonable.

My only issue is SQ. I can't as yet give my final opinion until I get at least 50-100 hours on them.

I can say the definitely do some things much better but I want to hold off on my final opinion.

Joel · Jun 5, 2014

Priaptor said:
Just got my KT150 tubes for my ARC REF75 and it was a plug and play install. No issues, at least day 1.

At this point I cannot comment on SQ as the tubes were right out of the box, all matched, but nothing broken in, so I am not in a position to comment other than to say, there is definitely more kick than with the KT120s-sounds like a much more powerful amp. Whether that turns out to be a good or bad thing we will see and refuse to judge at this time. Different isn't always better.

Curious if anyone else has made the plunge to these relatively new tubes and what your feelings are.

40 W per single tube... it's a lot of power indeed. I just tried the Ayon Orthos XS monaurals with 10 KT150 per channel.
I have really been impressed but did not compare with the same amp set with KT120... The Ayon could also work in triode mode with only 300 W per channel, and it was definitely enough to ignore in most cases the 400 W pentode mode.

jn229 · Jun 5, 2014

JackD201 said:
Are 150s drop in replacements for 120s or just in the Ref 75? I have a pair of KT120 monoblocks with autobias. Curious if I can swap tubes out.

I was contemplating the purchase of an old pair of Cary mono blocks, the CDA-100's. These amplifiers produced 100 watts from two 6550's per channel. Concerned about tube stress I phoned Cary, was told the KT-120 would be a drop in alternative. The KT-150's were a different spec tube and not to use them.

mep · Jun 5, 2014

I have heard both the KT-120 and the KT-150 tubes, but not in the same amp. I previously owned an ARC VS115 with KT-120 tubes, I now own a REF 75 with KT-120 tubes, and I reviewed a pair of Raven Audio monoblocks with KT-150s. From my brief exposure to the KT-150s in the Raven amps, I can tell you I think they do everything right from the very bottom to the very top. I will not be surprised after Priaptor has had sufficient time with the KT-150s if he comes to the conclusion that the bass seems both deeper and tighter vs. the KT-120 and the midrange takes on another level of 'reach out and touch it' realness. I couldn't find any fault with the top end either with the KT-150s.

Does anyone know if ARC has authorized the KT-150 for use in the ARC REF 75?

mauidan · Jun 5, 2014

Priaptor,

Where did you get your quad of KT-150s?

"plug and play," you didn't have to adjust the bias?

OT- What PC are you now using on your REF 75?

Priaptor · Jun 5, 2014

devert said:
Priaptor,

Where did you get your quad of KT-150s?

"plug and play," you didn't have to adjust the bias?

OT- What PC are you now using on your REF 75?

Just took out the KT120s put in the KT150s checked bias and it was in the perfect range. Nothing to adjust.

I have them burning in as I write this.

No issues

I am using my CAPS Zuma with a JCAT USB card powered by Core Audio's Kaia LPS with a LightHarmonics USB into an MSB Diamond plus into my Ref10.

The Kaia is dual rail 12v for the MOBO and 5v for the JCAT.

Love the JCAT Kaia combo.

mauidan · Jun 5, 2014

Priaptor said:
Just took out the KT120s put in the KT150s checked bias and it was in the perfect range. Nothing to adjust.

I have them burning in as I write this.

No issues

I am using my CAPS Zuma with a JCAT USB card powered by Core Audio's Kaia LPS with a LightHarmonics USB into an MSB Diamond plus into my Ref10.

The Kaia is dual rail 12v for the MOBO and 5v for the JCAT.

Love the JCAT Kaia combo.

Mahalo for the info on your set up.

In my last question, PC=Power Cord.

Priaptor · Jun 5, 2014

devert said:
Mahalo for the info on your set up.

In my last question, PC=Power Cord.

Using an Odin for the Ref75 direct to wall, Sains elsewhere except for the Kaia where I use a Transparent Powerlink. Using Valhalla II speaker cables. Kaia direct into the wall and the rest into Silver Circle 5

DonH50 · Jun 5, 2014

Do you get significant benefits without re-biasing them? Can most amps handle the higher currents? I dunno', just curious. - Don

Priaptor · Jun 6, 2014

DonH50 said:
Do you get significant benefits without re-biasing them? Can most amps handle the higher currents? I dunno', just curious. - Don

The bias on the ARC is based on the meter that shows you when the tube is bias correctly. When I put these in they were dead center on the bias scale so there was no need to do anything.

I now have 10 hours on them and they are lush and dynamic like I have never heard before. Listening to Sonny Rollins Road Show Vol 3. It's like listening for the first time.

DonH50 · Jun 6, 2014

I assumed the KT150's would require higher bias current for proper, or optimal, operation. If not that is great, of course.

MylesBAstor · Jun 6, 2014

DonH50 said:
I assumed the KT150's would require higher bias current for proper, or optimal, operation. If not that is great, of course.

Yes at least for the KT120s. But the 120 and 150s still work in the original circuit, operating as I understand it at a lower set point on the curve. The benefit is that they should last last longer. But you won't get all the power the tubes are capable of generation. There are now amplifiers built eg. different transformers, to work with these new tubes. I believe for instance, the Jolida amps are optimized for the KT150s.

Priaptor · Jun 6, 2014

MylesBAstor said:
Yes at least for the KT120s. But the 120 and 150s still work in the original circuit, operating as I understand it at a lower set point on the curve. The benefit is that they should last last longer. But you won't get all the power the tubes are capable of generation. There are now amplifiers built eg. different transformers, to work with these new tubes. I believe for instance, the Jolida amps are optimized for the KT150s.

Myles,

I am not sure of the physics involved or if ARC has their products optimized for these tubes, but I do know they have been testing them in house and as you said, have found they last longer and have almost 4000 hours on a pair REF250 monoblocs. We know they are considering or releasing a new product line called the Galileo based on the KT150 tubes and whether these products will have any difference in their transformers relative to their REF series, we will just have to wait and see.

When I plugged in my KT150s into the REF75 my bias meters were dead center as to where they were with the KT120s requiring no fiddling with bias settings, so I am not sure if the REF75, the last REF amp to be released by ARC was built with the KT150s in mind or not and if the lack of requiring any change in bias means that the circuits/transformers is optimized for KT150s. There has been some spinning going on the NET, but I have not confirmed it from ARC, that the transformers used in the REF75 is a "better more powerful" version than that used in the first REF amp, the REF150 and hence why so many are preferring the REF75.

I doubt that ARC will be "endorsing" these tubes at this time as I am sure they have a ton of KT120s in house to place in their current products and also being that the KT150s are more expensive than the KT120s would probably require them to raise prices.

Regardless, plugging these things into a REF75 is a fantastic upgrade.

MylesBAstor · Jun 6, 2014

Priaptor said:
Myles,

I am not sure of the physics involved or if ARC has their products optimized for these tubes, but I do know they have been testing them in house and as you said, have found they last longer and have almost 4000 hours on a pair REF250 monoblocs. We know they are considering or releasing a new product line called the Galileo based on the KT150 tubes and whether these products will have any difference in their transformers relative to their REF series, we will just have to wait and see.

When I plugged in my KT150s into the REF75 my bias meters were dead center as to where they were with the KT120s requiring no fiddling with bias settings, so I am not sure if the REF75, the last REF amp to be released by ARC was built with the KT150s in mind or not and if the lack of requiring any change in bias means that the circuits/transformers is optimized for KT150s. There has been some spinning going on the NET, but I have not confirmed it from ARC, that the transformers used in the REF75 is a "better more powerful" version than that used in the first REF amp, the REF150 and hence why so many are preferring the REF75.

I doubt that ARC will be "endorsing" these tubes at this time as I am sure they have a ton of KT120s in house to place in their current products and also being that the KT150s are more expensive than the KT120s would probably require them to raise prices.

Regardless, plugging these things into a REF75 is a fantastic upgrade.

I think the newest ARC amps are optimized for these tubes.

Priaptor · Jun 6, 2014

MylesBAstor said:
I think the newest ARC amps are optimized for these tubes.

I think so as well. This REF75 was already an amazing amp but with the KT150s takes it to a new level. I was once again skeptical of Carl's claim but he was once again correct. I now have close to 15 hours of playing time on them and it just keeps getting better.

DonH50 · Jun 6, 2014

MylesBAstor said:
Yes at least for the KT120s. But the 120 and 150s still work in the original circuit, operating as I understand it at a lower set point on the curve. The benefit is that they should last last longer. But you won't get all the power the tubes are capable of generation. There are now amplifiers built eg. different transformers, to work with these new tubes. I believe for instance, the Jolida amps are optimized for the KT150s.

Thanks Myles, that makes sense to me. The meters read the same because the bias point did not change, so no (or minimal) power gain, but yeah they should last longer running a little more in their SOA region. Also possible the KT150 is designed to provide more power gain than the KT120, natch.

Different transformers imply different output impedance, beefed up wire and core for the extra power, or both.

So are KT150's widely available now? Seems like this arose last year but they were very hard to find.

KT150 v KT120 Tubes

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