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In Reply to: RE: Congratulations! I still love my Cronus Magnum... posted by classfolkphile on January 22, 2017 at 12:47:13
I normally love EL34s but in my Cronus Magnum setup driving the Thiel CS2.4 speakers I found the EL34s to be lacking. Lacking in power it seemed. The sound was a little dynamically challenged.
The KT90 were better but I jumped on buying a quad of KT120s and that's pretty much what I've been using over the years. I should try some KT88's or 6550 but I'm wondering if these will produce at least as much power as the KT90's. If they're in the EL34 range, they won't be sufficient for my speakers.
I'd be curious to know which KT88, 6550, and KT66 you use. I haven't even tried NOS signal tubes since buying my Cronus Magnum a few years ago.
Follow Ups:
Abe,I've tried Svetlana (not Winged "C") EL34s; Black Treasure 6CA7s; NOS RCA black plate, NOS Sylvania, and new Tung Sol 6L6GCs; Gold Lion KT66s; Gold Lion KT77s; Svetlana Winged "C" 6550s; NOS GE 6550s; Gold Lion KT88s; Penta KT88SCs; EH KT90s; and Tung Sol KT 120s.
I agree with your assessment of EL34s in the Cronus Magnum, in addition to the thoughts I posted earlier.
The 6550s and KT88s sound significantly more powerful and dynamic than the EL34s with the "88s" sounding about as powerful as the KT90s. Even the KT66s sound more dynamic than the "34s" though they may not be enough for your Thiels.
Edit: The EL34s and KT66s put out 55wpc, the KT88s, IIRC, put out 90wpc, the same as the KT90s.
The 6550s I tried are not really available anymore and no one has suggested any current production is up to those standards.
I preferred the Penta over the Gold Lion KT88s for their additional refinement. The Pentas aren't available from my preferred sources anymore however, and the Gold Lions are very good. Buying them croy'd would probably be a good idea: they were a bit tight sounding compared to the Pentas.
The KT88s (and 6550s and 6L6/KT66 family) are definitely more linear than the KT120s.
I haven't really liked any of the new Tung Sol power tubes in my amps. I've tried their 6550s (in Quicksilver Mono 100s), and their KT120s and 6L6GC STRs (in the Cronus). They all have had an overly emphasized lower end that was also very thick sounding. To be fair, I didn't hear that in Mark O'Brien's KT120 equipped Apollo mono-blocks (with Hera pre-amp, and Wilson Alexandrias (?)). So maybe it's amp dependent?
The Gold Lion KT66s are the most balanced power tube I've heard, are very resolving and dynamic, and have an immediacy and refinement that remind me of SETs.
The KT66s didn't sound powerful enough to drive my 87db (8 ohm nominal, 3.9 ohm minimum) speakers in my old house. Strangely, in my new home in a larger room (with much higher ceilings), they do. More power would still be nice for absolute effortlessness but I don't hear the sound as at all constricted.
IME, a big improvement in sound can also be had with NOS small signal tubes.
Best,
Rob
Edits: 01/24/17 01/25/17
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Agree with most of the above comments on tube rolling. I own the Stereo 90 which is a very similar amp to the Chronus.
The Penta Labs KT88SC are a great tube in the Rogues. They are now being produced as the Preferred Series KT88 available at thetubestore.com. (supposedly the exact same tube).
Gold Lion KT66 (and GEC if you can find them) rock in the Rogues! 6L6gc great in the Rogue! EL34 not so great. Stock Tung Sol KT120 suck in the Rogues!(IMO).
Input 12ax7s have big affect on the sound. RCA blackplate 12ax7, Raytheon black plate 12ax7, Siemens ECC83, Matshushita 12ax7 and (original) Tung Sol 12ax7 are best, also GE, Raytheon or Sylvania 5751 blackplates.
Cant comment on drivers (12au7) my Stereo 90 uses 6SN7 drivers.
Enjoy the Roll!
Edits: 01/25/17
Thanks for posting your comments on various tubes for Rogue. I'm keeping a printout handy.
BTW, I noticed in your profile that you use Kimber 8TC speaker cables. Have you tried anything else and compared directly against the 8TC? I have found the 8TC to be consistently bass shy compared to many other speaker cables. And this was on a few amps, not just my Rogue. Just a thought.
Hi Abe.
I have tried a dealer loan of some Nordost flat cable once and found that thin compared to the Kimber. That was several years ago when I was running Totem Hawks with the Rogues. Also tried anti cables and sent them back, preferring the Kimber.
That said I have thought about a cable upgrade for some time. What type of wire do you use in your various systems?
I had Kimber 12TC: they were pretty good as long as they had gold plated or copper connectors: otherwise too bright. You might want to try Triode Wire Labs speaker cables: less expensive than the 12TC and much better: more resolving with much better tonal accuracy. (Not as good as my Kaplan Cables but less than half the price of those.)
Thanks Rob,
That's a lot to think about! I'm making a printout of your post for when I get the urge to buy some tubes.
You're welcome.
Another thought: like your Thiels my speakers are also time aligned and phase coherent. Eliminating the bypass caps (by cutting one wire between them and the coupling caps) gave a much more coherent presentation (you can obviously always re-solder the one wire if you don't like the result).
I found the bypass caps smear the time alignment causing the treble to be way too far forward relative to the mid-range and bass. I didn't really notice any loss of frequency extension. But in any case, I then had Rogue remove the cheap bypass and stock coupling caps and insert Mundorf Evo Silver/Gold/Oil (the only ones that would just fit) for more resolution, extension and refinement. For me it was well worth the $400 cost.
Space heaters are not exclusive to you tube guys!
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