Anybody tried KT120 tubes on Conrad Johnson amps?

HI Kkurtus,
What is a Power 2? How much did you pay for the KT120's and how many of them are in your amp? It's my understanding that they are significantly more expensive than good 6550's. Where did you buy them?

Are they better that your 6550's? In what way?

Sorry, lots of questions.

Sparky

HI Br3098,
Basically, I agree with your last sentence. However, I think there are exceptions. For example, I have modified my ARC D250 Mk II Servo amp. It was designed in the mid 1980's. At the time, it might well have been the finest amp you could buy. J. Gordon Holt (RIP), the founder of Stereophile, thought so. I bought mine used in the early 1990's. By the year 2000, one of the things that had changed since the amp was designed was capacitor technology. The D250 had the finest Rel caps available at the time the amp was designed.

Around 2000 I decided to replace all the interstage coupling capacitors with the latest and greatest. MIT was my manufacturer and technology of choice. Unfortunately they did not manufacture caps with the necessary voltage ratings. In fact, no one did with the capacitance value I needed. Were the original Rel caps a custom design for ARC? Could be. They certainly were not in the catalogs.

After a long search I decided to request a custom design from MIT. They agreed and we struck a contract (I had to pre-pay). They were expensive which was mostly a result of the limited production run of 20 pieces. Of course, even their off the shelf standard capacitors were expensive. Mine were more so. After 6 months I had the capacitors.

The new caps definitely improved the sound of the amp. Better resolution, transparency, and speed. This amp was already excellent in these areas. I'm certain that if the amp had been redesigned the caps would have been replaced with more modern improved designs. I simply anticipated the redesign that never happened.

At this time I do not plan on replacing the 6550's with the new KT120's. However, once more is known about the KT120 performance in older amp designs, I might change my mind. The KT120's will not result in more power but might offer significantly longer tube life.

And there have been no downsides to my cap upgrade. The amp just keeps chugging along and I love it. It's truly a great amp.

Sparky

HI Guy's
I totally agree. A cap upgrade is pretty safe and I believe I indicated that. I just wanted to not discourage folks from certain kinds of upgrades that are safe and can really add to the sonic experience. Tubes are a different story and should be done very carefully.

My guess is I will never upgrade to the KT120. The differences with just the heater current, while not great for a single tube, adds up when you consider that I have 16 6550's not counteng the regulators. The resulting added current may well overload the heater supply. I'm very curious about others experiences.

Sparky

HI Hifigeek,
Why in the world would I follow your advice? In a previous thread you made claims that I questioned. I asked you to back up your claims by telling us what your test methods were. This is a fair question. You refused to do so. Scientifically, your attitude is simply not acceptable and inspires suspicion.

As far as I'm concerned you are full of hot air and are just trying to impress the naive. But you can't fool me. With me you have zero credibility. I have all the test equipment and knowledge to stand on my own. Your input is not trusted or wanted.

Sparky