My Siemens E88CCs arrived today. Listening commenced. Initial assessment: real close—tough to improve on “great.”
It’s also tough to casually compare tubes A-B. I compared the stock V3 with the Pietus Maximus (A-C) in anticipation. Then compared V3 with the Siemens tubes vs. the PM (B-C). That gives me an indirect (A-B) = (A-C) - (B-C).
The E88CC is objectively a better tube than the 61NP (better transconductance, for instance). But I don’t hear a game-changing revelation in sound performance.
The Siemens are not excessively bright or analytical. I expected more of that than I'm hearing. If anything, the stock tubes might sound a bit leaner.
Maybe the Siemens expand the contrast between V3 and PM just a bit, and sound slightly more authentic.
The occasional excessive ring/reverb from the V3 I noted last time might be less apparent with the Siemens. The PM delivers discrete, neatly packaged notes. The V3 splays them out a little more. Most of the time, the latter is more favorable, but sometimes it sounds off.
Part of the issue here is that PM is really good, and competitive with tube sound. The stock tubes match the amp's design and sound great. It’s too soon to declare whether the Siemens were worth the upgrade. Everything sounds great. That's a good problem to have.