Update-I reinstalled the cover on my ARC Ref 75 last night before the listening session started because I don't care for the looks of the amp sans cover. And yes, the cover fits nicely over the KT-150 tubes. I have owned many tube amps over the years including a bunch of ARC amps and many if not most of them looked better without their covers and that is how I used them. I do think the Ref 75 is a handsome piece of industrial looking art and removing the cover destroys the effect.
So now I have two nights on these tubes and night two was better than night one. You will notice many of the good things these tubes bring to the table upon first listen mind you. Even though using the KT-150s in a circuit that was designed for KT-120s doesn't take advantage of the extra power output the KT-150s are capable of, they damn sure make your amp sound like it has increased headroom. I heard this with the Raven Silhouette monoblocks I reviewed when I switched over from real, no kidding, NOS 6550 Tung-Sol tubes to the KT-150s. Better deep bass extension (sounds like another 1/2 octave extension), better midbass articulation, just better everything from top to bottom. That same sense I had of the KT-150s just loafing along and never sounding like they are working hard and being taxed I heard in the Silhouettes I'm hearing again.
Based on what I heard with the KT-150s in the Raven Silhouettes, I was excited to hear them in my Ref 75 and I'm not disappointed. Some of the people who own the Ref 75 beat me to the upgrade and all of the comments I have read are positive. It's easy to understand why once you hear these tubes. Carl from NOLA is real high on using the KT-150s in the Ref 75. One of the tricks that I think the KT-150s pull off is they resolve more spatial information in your soundstage. It defines not only the boundaries of your sound stage in terms of height, width, and depth, it does a better job of placing instruments and people within those boundaries and allows you to see/hear the space around each of the instruments and people with greater clarity and focus. And Jumpin' Jehosafats, you might just hear some information within those more articulated boundaries that has escaped you and the resolution capabilities of your system before.
I can't wait to hear my system with the Viero cables again because those speaker cables bring the same type of improvements as the KT-150s do and this is the first time my system has sounded this good since I packed up the Viero cables and sent them to Myles for his follow-up review. I know that Myles told me to quit whining, but I would by lying if I said I haven't been doing a little whimpering now and then because I knew what I lost when I disconnected those cables from my system. The combination of the KT-150s and the Viero cables should be a frickin' knockout.
If you have a tube amp that can safely run the KT-150s without imploding, you need to quickly go forth and order ye a set.
