Not sure which socket is which but I pair the RCA BP 6CG7s on the left with some Tung Sol GP 6CG7s on the right. Full, warm, and natural sounding (with the most natural treble response I have ever heard). This is with very neutral and slightly dry-sounding equipment in the chain. The RCAs are responsible for the bass/mids response, and the Tung Sols for the treble.At @Paladin79's recommendation over a year ago, he recommended to me some Soviet Reflektor ECC88 tubes for the cathode follower sockets for my Freya N. They are inexpensive, readily available, and made a positive difference over the stock tubes that came with my Freya. For the past couple of weeks I've had my new set of Telefunken's in the differential gain sockets. A couple of weeks ago I started hearing some random hissing noise while listening to music. I traced it to one of the follower tubes, thankfully, so I pulled them and replaced with the stock tubes or similar spares that I have on hand. In the meantime, I soaked the Rockets in Deoxit for over 24 hours, gave them a thorough cleaning, and brushed them with Deoxit Gold.
Anyhoo, with the non-Reflektors the music was lacking something or rather, I was missing something that was there before, some ingredient that gave the sauce that extra thing that kicks it over the line from good to very good. Last evening I put the Reflektors back in and settled in for more of Apple Music's Jam Band playlist while I read some more of Tolkien's "The Silmarillion" (great book, BTW, not at all the slog I was warned that it would be). The good news is that there was no hissing or other unwanted noise. The music sounded amazing. Detailed, warm, and oh-so-tubey! The chain was M1 Mac Mini->Gumby->Freya N->Lokius->Sys->Magni Piety>HarmonicDyne Zeus Elite headphones.
For those of you with Freya N's, what tubes are you using in the follower sockets? Any other recommendations?
<Edited to correct socket type>
You can't go wrong with the RCA BPs ($40 a pair), and they are way easier to find than the fabled Raytheon Black Plates. Tung Sols ($50 a pair) IME has to be paired with tubes that can compensate for their lackluster bass response (such as RCA BP), though the treble is to die for.