Rogue Audio Cronus 12AU7-12AX7 tubes choices

I own a Rogue Audio Cronus amplifier since two weeks and I want to upgrade the preamplifier section tubes which are 12AX7 and 12AU7.

First, I'm wondering the fonction of each tube. I don't want to replace the one for the phono section if it is so because I don't use this phono. What are the fonctions of each preamplifier tubes on the Cronus?

Second, I'm looking for a musical, engaging and well balance sound. What are your tubes suggestions?

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Slightly off topic, but I am curious as I am looking to upgrade my existing tube int. amp and am considering a Rogue along with 3 other brands: What do you think of the Cronus as shipped? Did you purchase it new or used? What prompted the tube rolling?
Try some Telefuken 12ax7 smooth plates, or Mullard 12ax7. A little pricey but good tubes. I use them in my VTL 5.5 tube pre amp. 2 Tele 12ax7, and 4 Mullard 12at7.
I own a Cronus and like it a lot. It is a solidly built piece that is reliable and backed by very good service.

It sounds good out of the box but can definitely be greatly improved by tube rolling and fuse upgrades. The latter adds a significant amount of resolution.

As for the tubes, the center 12AU7 is the preamp tube. The other two 12AU7s are the amp section drivers and the 12AX7s are the amp section phase splitters. The phono section does not use a tube.

For the preamp tube I prefer either NOS Raytheon black plates or the new Shuguang Pavane 12AU7. NOS Mullard CV4003/12AU7 sound wonderful as well but I've had three of them go noisy in this position. I do like this Mullard best in the driver position, however (Upscale Audio carries a driver grade level which is much less than a preamp grade one). Raytheon black plates also sound very good in the driver section.

For the phase splitters at a reasonable price, I like the new Tung Sol 12AX7/ECC803S gold pin (the regular Tung Sol might be good also but I haven't tried it yet). The best tube I've had in the position is the NOS GE 12AX7 long plate but they're expensive. I also like Japanese 12AX7s from the '70s (usu. made by Mashushita, various labels).

I find the stock Sovtek 12AX7LPS tight and forward sounding. I also find the stock driver un-resolving.

There are also better power tubes available. The SED EL34 and the Genalex re-issue KT77 for example. I prefer the Genalex KT66s (biased at 32.5 ma) and Shuguang Black Treasure 6CA7s (the latter very expensive) most of all but these require socket extenders (available here under octal socket savers:

Good listening.
Thanks for your suggestions. For sure, I'm also planning to upgrade the power tubes with SED Winged "C". I already had Winged "C" KT88 with another amplifier and the improvement over Valve-Art stock tube was incredible.

I'm very happy with the Cronus. I purchased it new to my local dealer here in Montreal, Canada. For me, it's important to have the warranty with a tube amp because they are not the most reliable machine on earth but the sound they produce worth it.

Already, the "out of the box sound" of the Cronus is great but I know that it can be improved with better tubes.

To Michael, which are the other candidates? On my side, I was interested also by Leben, VTL and Luxman's EL34 based designs.

Finally, anyone tried 12AU7 NOS RCA clear top with the Cronus?
Why don't you take some time to get familiar with the sound of your new Cronus before you start swapping tubes. That way, you can better ascertain what changes you want to make. Just a thought. Enjoy.
I have the Cronus Magnum version which allows for KT 90s - the amp came Sylvanis in both the 12ax and au positions, switched the 12ax to Tungsol 5751s and the 12 aus to RFTs which to me sound similar to some RCAs I have. These added a little more warmth that I was after.
I agree with Tpreaves.....Enjoy your new Cronus "as is" before you start rolling tubes. It sounds really, really good with the stock tubes. Then, once you have the desire to try new tubes, there are a lot of ways to go.

For me, my Cronus, being fed by my Rega P3-24/Exact 2/TTPSU and Rotel RCD-1072, through my Vandersteens, sounds better after I did the following : an RCA NOS 5814 to replace the center EH 12AU7 gain stage tube, a pair of GE NOS Five Star 5751 "goldpins" to replace the Sovtek 12AX7 input tubes, and a pair of GE NOS 12AU7A's to replace the EH 12AU7 driver tubes. I then replaced the original Svetlana EL-34's with a beautiful matched quad of Genelex Gold Lion KT-77's.

All this "tube rolling" was done after some pretty nice conversations with Mark and Nick at Rogue Audio, and I'm glad I followed their advice. They are a pleasure to work with.

Good Luck, and Happy Listening !
I agree with the above comments about enjoying the amp "as is" for a while. I'm doing this since I have it and I already have many hours of intense listening on it.

At that time, I'm looking for tube suggestions from you "Goners" as I want to have an idea about where to go and look and to be ready if a deal pass by. But I'm not on a hurry.

About the center 12AU7, mine is totaly blank. I don't have any idea of what brand and year it is. Should I ask Mr. O'Brien what it is? Do you have the same kind of tube on your Cronus?

I know this is off topic, but I've seen your postings on Audiogon and HUG in relation to the Harbeth SHL5. I don't know if you are still using that speaker, but it's one I've been most interested in. Are you using the Cronus with the SHL5? I saw that you had some experience with the Luxman integrateds. I believe you had the 505u, and one of the Class A amps, and was wondering why you chose to go the Cronus route after hearing the Luxmans. I've been interested in the Cronus, and have heard the Magnum version at a local dealer , but was hoping to hear your experiences with various Luxmans and Rogues with the Harbeth. I haven't had a chance to start auditioning amps yet, but would appreciate anything you could share about your experiences. I was also wondering if you had any thoughts on the strengths of the Cronus relative to the Magnum version and Luxman integrateds. Any of your thoughts on these questions would be appreciated. I’d be willing to spend the extra money on the one of the Luxmans or the Magnum version of the Rogue if it were worthwhile, but would prefer to save the extra money for music, so it’d be great to hear someone who has heard the Rogue/Harbeth combination after having heard the other combinations. So far, I have the usual suspects of LFD and Luxman on my audition list, based on reviews and forums, but there hasn’t been much about the Cronus/Harbeth combination, aside from a brief mention in Stereophile re: Son Ideal at the Montréal show last year.

Thanks in advance for your time!

Well, let's continue off topic because I don't have other way to communicate with you. First, I still use Harbeth SHL5 and I really appreciate them. In the last year, I had the chance to try many amplifiers with them. I had a great time with two Luxman and I like both the L-505u and L-590AII. The 505u have a dryer bass with the SHL5 but on every aspects, the L-590AII is more interesting with these speakers: voices so natural, fabulous sound of strings instruments, easy on the ear, refine, musical and organic.

The main reason I went back to a "cheaper" amplfier ($2000 vs. $9500) is that I judge that in my system and budget limitation it wasn't worth it. So, I switch back to the Rogue Audio Cronus, which we talk in this thread.

Surprisingly, with the Harbeth, the Cronus does things that even the L-590AII didn't. Good for me! The soundstage is wider and deeper and the timber of intruments are more accurate.

The influence I had to go with the Rogue is that my Harbeth dealer often demo them with Harbeth speakers and that combination plays MUSIC! So, I demo the Cronus at home and enjoy it. It was my first time with EL34 tubes amp and I like it so much. I don't have any regret about the switch I made and I've got back few thousands in my pocket.

Finally, if you'd like to have other information on this subject, we could create a new thread. I'll be happy to contribute.

Let me know.
I've tried RCA clear tops in both the pre-amp and the driver positions. I found them lacking in body/fullness in the former but, with warm pre-amp, phase splitter and power tubes, good in the driver openings. They have really nice, extended highs.
Is there any of you that use 6211 tubes instead of the 12AU7? I know that they are not compatible with every amplifier but when they can, they are a good improvement.