The Nautilus is awesome. I was going to leave it at that, but here are some early impressions.
I haven’t A-B’d it against the Pendant yet, but it has a familiar fast, neutral sound, so it’s not a huge leap from the Pendant in terms of sound signature, although I suspect I will notice differences when I get around to comparing them.
Plenty of power. The Verite sounds nice and relaxed using the 100 ohm output, but I think I prefer 300 ohm, because the Verite suddenly becomes locked into the rhythm of the music, and the imaging is clearer. From memory (which is faulty), the ZMFs did not sound as controlled on the Pendant’s “High Z” output. The Stellia sounds awesome using the 32 ohm output.
Having gradually switched from stock to NOS tubes over a number of days, I can say that I could have stuck with the stock tubes and enjoyed using the amp, with the exception of the JJ 12ax7, which I found sucked all the warmth out of the music. I also found that the 12ax7 had too much gain for my Stellia, meaning that I had no practical range on the volume knob. Switching to a 12au7 gave me more flexibility with volume.
Switching from stock JJ KT88 and Tung Sol (new production) 5AR4 to Amperex GZ34/5AR4 and Tung Sol (NOS) 6550 gave me a little more texture, stage and holographic imaging. The texture of synths and strings is amazing. Bass is well controlled and very rhythmic. The stage is nice and wide, and when I listen to a piano concerto, I can follow the pianist’s hands from one end of the keyboard to the other. And I’ve noticed the height of the stage, not just the width, i.e. some sounds are above my head and some are below.
When using the stock power and rectifier tubes, I had preferred using the Mazda 12au7, which didn’t have the warmth of the Mullard, but had a more uniform sound, giving me good highs and lows. But with the NOS tubes, the Mazda has slightly too much emphasis on the upper mids and highs, so I’ll try one of my other 12au7’s to see if I can find better synergy. The curse of tube-rolling I suppose, where you find the perfect combination, you’re happy for one day, and then you change one tube, which causes the whole house of cards to fall down, and you have to start again.