I recently bought a UFO25 that Groovy was selling for his brother. The amp is beautiful like you said, more striking in person. I was previously using a UFO with 25th mods and really liked it, I thought the transition would be a simple one, nope! I also bought the full Cryotone compliment for the UFO25. When I first got the amp I decided to just transfer the tubes from UFO and use the Cryotone VR tubes. Mullard GZ33, SV83's and an Amperex 6DJ8. The sound was good, and sometimes great then sometimes just not right. This is where a long string of mistakes and assumptions occurred. I went forward with the assumption of "if something isn't right then look up the chain for the issue". I knew my turntable was setup good, the tubes in the ZP3 were to my liking, so I went nuts with rolling tubes in the CSP2+. Again went though good, bad and ugly. At this point I put the CSP2+ back where it was. I now dove into the UFO25 tube rolling. I replaced the Cryotone OA3 with a pair of OB3's. Better, much better, but still not happy. Rolled the input VR tube and that wasn't it. In the UFO I REALLY liked the SV83 and stubbornly ignored rolling them, they just can't be the issue I kept telling myself. One night I finally put in the Cryo 5AR4-WC v2, EL84-WC and ECC88-WC. B I N G O ! ! ! It was the SV83's that just didn't work for me in the UFO25. I've kept the Sylvania OB3's and a Raytheon OD3, the Cryotone VR tubes just don't sound great to me, with them in the sound is too edgy, sounds didn't "end" well, ragged and edgy. The sound also leans a ton towards bright which is no good for me. The sound just had a huge bump in the upper mids into the highs, some may like that, to me it was quite fatiguing.

I felt the same as you about the "tiny" 5AR4's, I liked the sound of the larger tubes but for my room, system, ears that tiny 5AR4 works better than Mullard GZ32 or GZ33 which really surprised me.

As far as going full compliment of Cryotone, my personal opinion is the rectifier, output and input sound great, the VR tubes I wouldn't recommend - BUT, they may work for you.

Good luck getting it dialed in, once you get close the experience is jaw dropping!

Congrats on your 25, Bri. I mostly concur with Sean on his thoughts. I have not used the Cryotone VR tubes but found glutton supply of inexpensive 75c1 available online to be perfectly suitable.

There is a magical synergy with the Cryotone 6p15ps and their ECC88. In my room with the music I listen to this combination is the best I have been able to find for energy, detail, and a tightly controlled low end that is extremely present and satisfying but not inflated at any particular low frequency.

Hi HiFi Bri,
Congrats on the UFO25! I saw photos in your other thread and it looks stunning. The grain on the walnut base is beautiful. Looks like you have a great setup going!

I’ve had mine for a little over a year now and it really is an amazing little amp. I found that the bass got fuller and more textured/controlled after about 250-300 hours. So you should be pleasantly surprised. I’ve also tried several EL84s that I had from a prior amp, as well as the Cryotone EL84 and can tell you, the Cryotone sounds clearly better than the other EL84’s in this amp. There are a lot of discussions of the Cryotone EL84 and some comparisons with other EL84’s and the Cryotone 6P15P, that may be worth perusing, before you go for it. I currently have Russian 6P15P-er tubes in, along with other NOS tubes, but am awaiting one more 5U4G-WC, to put back the full compliment of Cryotone tubes to see how that works out. I also use other RCA/Raytheon/Sylvania VR tubes with the Cryotones in the amp, but will be using the Cryotone EL84 and ECC88’s for my amp and preamp, once I receive the other 5U4G. Have you played around with the hi/lo speaker impedance and input bias settings? I found them to have significant impact as well. Enjoy your new amp!