My narrow tube selection guide for most transparent, detailed, darker and bassy sound:
Input tubes:
You heard nothing even close good if you never tried NOS Russian 6N30P or 6N23P tubes! The clarity, well controlled DEEP bass and very very natural sound these produce is really something! I myself prefer 6N23P, but they are really close. With 6N23P you get some extra gain. Good bout those tubes is that they last 10.000-20.000 hours.
Voltage regulators (input stage):
Again you can chose from OA2-OD2, but to be honest I didn’t find big difference between different input regulators. So I have chosen one witch looks better (with huge orange glow all around): STR75/60 (VR75).
Output tubes:
I have tried almost everything, only after I found Psvane 6CA7 Treasure tubes (or any other real 6CA7 tubes) I felt first time that tube amplifier CAN BE at same time transparent, sparkling, super detailed, with deep bass and sonically silent. Only one problem here with OA3 voltage regulators 6CA7 lasts max. 1000hours, it is absolute maximum.
Another tube for output with really similar character (maybe little bit more bass and just with a little bit less musicality and accuracy) is: Tungsol KT-120. It was really hard to chose between Tungsol KT-120 and Fuller 6CA7 (dark bottle). Note that with KT-120 there is no space for dumperd with Torii, because this is tube is big and fat...
Voltage regulators (output stage):
There is 4 different type of voltage regulators you can chose from, OA3 OB3 OC3 OD4 (from most accurate and bassy to less accurate and less bass). If you run your amplifier with EL34, KT77, KT88 or KT-120, then chose OA3 regulators. If you want to use 6CA7 tubes in output stage then better to us OB3 as regulators (to at least double lifetime of your output tubes).
Rectifiers:
There is 4 winners, bad thing is that they are all rare vintage tubes. There is a lot of different rectifiers with different character in sound, but most of them add some grain and dirt to your music and makes you bass tired.
Best of the best is of course Western Electric 422A (WE 422A, holy grail of rectifiers). With this tube you get everything you want from perfect tube. Problem is that it is hard to find one NOS tube (like all unicorns...). I have invested in 3 of them (for the future…). Don’t be sad because there is still three more tubes that are pretty close to 422A: Cossor 52-KU, Mullard CV378 and USAF-596 (United Electronics). KU52, CV378 and USAF-596 are also magical tubes. If you chose from these three you can’t go wrong!
Here's my dream tube combination which I have reached:
Torii MK3 amplifier:
Input tubes: 6N23P
Voltage regulators (input stage): STR75/60 (VR75)
Rectifiers: USAF-596 (United Electronics, ”Mighty” 596)
Output tubes: Fuller 6CA7 (dark bottle)
Voltage regulators (output stage): Sylvania OB3
CSP2+ pre-amplifier:
Input tubes: 6N30P-DR
Rectifier: Western Electric 422A (WE 422A, ”Holy grail”)
...in case you need some fresh tracks to test your system (and tubes), I made this playlist in Spotify:
https://open.spotify.com/user/1122517992/playlist/4u5GJfcaFp2QroOQezHl1j?si=G5is...