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I am very happy with my final choice, which are JJ EL34IIs. They sound lovely in the Rogue Audio Cronus Magnum II. Without changing the overall character of the amp, which is quite neutral and big/bold, the sound is definitely a bit rounder in the bass, and generally warmer with sweetened treble. Subtle in all regards, which is great, but noticeable in a pleasing way.
Note that I run this amp with a Music Hall DAC with tubed buffer stage and Klipsch Heresy II speakers, and I'm sure different systems will react differently. I know, for example, of at least one inmate who didn't get good results with the original EL34 Cronus with his low impedance and less efficient speakers so, as always, YMMV.
As far as choosing JJ, I'm very happy, knock on wood. The tubes are silent and sound strong and big. They are exactly what I was hoping for and cost $125 for a matched quad with 24 hour burnin from the Tube Depot. The Russian options, and most of the Chinese options, were, naturally, a lot more expensive. So there's that too.
Separately, I just bought a Chris Keller-built ST-70 amp for my "main" system, which he is sending with JJ 6A7C power tubes, so I'll post a second update after comparing those tubes to the EL34IIs in both amps. And I'll post my impressions of his amp generally at some point.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Follow Ups:
I've been running an all solid-state setup as my primary for a few years but decided to bring the Cronus Magnum (not the II or III) back into the rack earlier this week for a listen. It sounds so nice - which reminds why I've never sold it. That Cronus Magnum has been my keeper for over a decade now whether it's been active in my audio rack or not.
I've been running it with KT120 tubes but decided to swap in my older set of EH 6CA7 the other night. In some respects I think I actually prefer the 6CA7 vs KT120. As an aside, I was told by Manley many years ago that the 6CA7 is like a 'rugged' EL34. That was their generalization years ago when I had the Manley Neo-Classic 250 monoblocks. When I retubed them Manley recommended the 6CA7. Long story I won't go into here.
In any case I'm presently running my Cronus Magnum on EH 6CA7 and it sound great! I ordered a quad of JJ 6CA7 today. Can't seem to find KT120 anywhere and I might just prefer the 6CA7 anyway.
I paid $140 with burn-in + FedEx 2-day Shipping from TubeDepot.
I now have a custom built ST-70 I just posted about separately, and I chose the 6CA7s from the builder/seller. So now I have a quad of JJ EL34IIs from the Tube Depot in my CMII and a quad of JJ 6CA7s in the ST-70.The 6CA7s sound great in the ST-70 and I'm very happy with the EL34IIs in the CMII in their respective systems, but I definitely plan to swap them to see how each tube type sounds in the other system. I look forward to hearing your impressions. I note that I have efficient and easy load speakers in both systems, so your Thiels likely respond a bit differently?
I do not like the JJ 12AU7 in either my CMII or my Rogue RP-5 preamp, and I replaced them with reissue Gold Lions, which are great. But I'm very happy with these JJ power tubes and a big fan of JJ now. Not being Russian is a good start, lol, but they're really nice sounding too. Now I'm thinking of trying their KT88, KT77 or KT66 at some point soonish as well.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Edits: 03/03/23 03/03/23
Yes, it will be interesting to compare notes on these tubes in the CM. I look forward to it.I've been running my more efficient Tannoy Definition D500 towers lately (91dB 6 Ohm nom.) and have the power hungry Thiel CS2.4 speakers stored in the closet.
When I ran the Cronus Magnum on my Thiels I really needed every once of extra power so I was pretty much limited to using the KT120 power tubes. The EL34 / 6CA7 were noticeably compressed sounding vs the KT120. But this is no longer the case with the Tannoys which allows me a broader choice in power tubes for the CM.
As an aside I emailed Rogue a couple days ago. Here' my email exchange with Nick:Hi Abe,
We have never used he 6CA7 in production for any of our products, so I don't know how their longevity will compare to the EL34 tubes. The GL KT77 is a nice sounding tube which is very similar to the EL34 but should provide longer tube life. The recommended bias setting for KT120's is 35mA and it would be 30mA for EL34, KT77, and 6CA7 tube types. Of the 3 tubes you have listed, I would expect the KT120's to provide the best tube life in the Cronus.
Best Regards,
Nick Fitzsimmons
Rogue Audio Inc.
545 Jenna Drive
Brodheadsville, PA, 18322- - - - - - - - - - - - - - - - - - -
From: Abe Collins
Sent: Friday, March 3, 2023 11:49 AM
To: info rogueaudio.com
Subject: EL34 / 6CA7 / KT120 Bias for Cronus Magnum ?Hello -
I have an older Cronus Magnum (not the II or III) and have been happy running it with a quad of EH 6CA7 tubes or Tungsol KT120. I have a few quick questions I was hoping you could answer.
Is the 6CA7 considered to be a more "rugged" EL34? I heard something to that effect many years ago. Will the 6CA7 have a longer tube life in the Cronus Magnum vs the EL34?
Your BIAS recommendations for:
- EH 6CA7
- JJ EL34
- Tungsol KT120I've been biasing them all at 35ma but this may not be quite right. Which of the above tubes should last the longest in my Cronus Magnum?
- - - - - - - - - - - - - - - - - - -
Cronus Magnum / Benchmark - Polar Opposites? Sort of:
Edits: 03/04/23
I run Heresy IIs with the CMII and am running Devore Fidelity Super Nines with my new ST-70, which are 8 ohm nominal and around 91 db efficient. Both systems have great dynamics and solid bass with those amps and the tubes in them. Still, I might go for some JJ KT88s for the CMII at some point given the tube life caution from Nick.
Your email exchange is consistent with my call with Nick last week, though I'd not specifically asked about the KT77.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
I didn't mention the KT77 to Nick but he offered it up as a nice sounding tube that's more rugged than the EL34. I've never heard one.
News Flash!
I ordered my JJ 6CA7 from the TubeDepot on Friday and they arrived Sunday afternoon. I specified FedEx 2-days [which is 2 business days] but I suspect they got here so quick because the main FedEx hub is in Memphis TN and TubeDepot is in Memphis.
Time to play.
They were America's answer to EL34s. Many people prefer them, and yes they supposed to be more rugged.
Enjoy,
Jack
Jack thanks for your comment on the 6CA7. Here's the long story on how I was introduced to them over 10 years ago.I owned a pair of very hefty Manley Neo-Classic 250 monoblocks that took 10 EL34 tubes each and I felt it was time to retube them. After the EL34 retube some of their plates started glowing red and ended up popping a handful 10-Ohm cathode resistors. Manley offered to take the amps in for repair free of charge but I really didn't want to ship these beasts at 80-Lbs ea boxed. Manley service [Paul in AZ I think] was kind enough to send me a batch of replacement resistors, a schematic, and more EL34 tubes.
I replaced the resistors and the tubes but a few resistors popped again as some of the tube plates glowed red. Paul commented that they've been having problems with EL34 tubes and said that it seems some of the manufacturers "lost the recipe" for making them reliable - funny comment but he then suggested I give up on EL34's for a while and try 6CA7 tubes instead.
I ended up buying 20 6CA7-EH [10 per monoblock] and never had a problem again. I eventually sold the amps as I wanted something much more compact. That led to my Class D journey but that's another story.
Manley Neo-Classic 250 Repair on my makeshift workbench in our previous home:
Edits: 03/04/23
Interesting. I've never been a huge fan of EL34s, but my experience is somewhat limited. They came with the original Rogue Cronus. My Jadis DA-60 amp could take them, but I preferred 6550s/KT88s. I actually have a fair amount of EL34s laying around. I'm sure they can sound good in the right amp. I didn't think to try 6CA7s though. There have been issues with KT-77s in the past as well, something to keep in mind.
I've been craving tubes again, not SE, but lowish powered PP. Looking into 6L6, EL84 or possibly EL34/6CA7s. Taking my time this time around.
Enjoy,
Jack
I'm no expert on tubes but in my recent experience with the Cronus Magnum and my more efficient Tannoys [vs the Thiels now in the closet], I think I prefer the 6CA7 over the more powerful KT120.
My EH 6CA7 and just plugged-in JJ 6CA7 sound more robust and rich, and a little more 'fat' compared to the KT120. The KT120 seem more neutral and tight, more top end. They're not 'thin' but relative to the 6CA7 they may seem so.
Is not a great sounding tube. I know they are standard issue with new Rogue amps and many others, but I think that is because of reliability and power output, not sonics. They are powerful, with good bass and dynamics, but dry sounding and lacking harmonic bloom through the midrange. Many people love them, but mostly because they have not tried something else.
I think KT66 has the best treble of these tube types, along with a holographic midrange completely lacking the upper bass bloat typical of KT88/Kt120 tubes. Definitely a more linear sound. Unfortunately you lose some bass heft (although the bass is tight) and about half the power.
The original Rogue Cronus came with EL34 tubes if I'm not mistaken. My Cronus "Magnum" came with KT90's but I'm not sure if those were factory tubes as I bought mine used.Although my old Cronus Magnum is electrically compatible with the KT120 [per Rogue] I needed to change the chassis top. The older chassis top hole cut outs were too small in diameter for the larger base on the KT120. I purchased a new chassis top from Rogue years ago.
I didn't have much choice but to run the more powerful KT120 with my Thiel speakers. Now that I'm back to my more efficient Tannoys [91dB 6 Ohm] I am able to experiment with a wider variety of tubes.
I have a quad of EH 6CA7 that sound wonderful, overall much nicer than the KT120 IMHO. On the other hand, I just got my fresh quad of JJ 6CA7. These JJ's are very robust and deep in the bass and lower freqs in general but they're not very detailed and lack top end. In a word they are rich and dark. Ok two words. I'm leaning more toward my EH 6CA7 which are more balanced sounding.
Edits: 03/06/23
I'm becoming a JJ fan. Glad to hear their 6CA7s are working out for you, knock on wood. I'll swap mine into the CMII in due course.
Slovakia for the win.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
I haven't compared any actual EL34 tubes in my CM, just the EH 6CA7 and JJ 6CA7. I received the new JJ 6CA7 on Sunday. In my short auditions of both tubes I found the EH to be more balanced.See my comments to Mendel .
Edits: 03/06/23 03/06/23 03/06/23
I just swapped the JJ 6CA7s in and have listened to one album only as of now. My initial reaction is very positive. They sound more robust and linear than the JJ EL34IIs and better overall if not quite as sweet. I'm not noticing a lack of high end detail, but they are darker. Of course that's JJ to JJ. And with Heresys. I don't have other brands to compare to in the EL34 family. Next will be my thoughts on the EL34IIs in the ST-70.I'll listen more, but so far I feel like I'd only change back to KT120s (or 6550s or KT88s) to preserve tube life and not for sonics.
EDIT: My tubes have now burned in for over a week of fairly frequent play time.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Edits: 03/07/23 03/07/23
My comparison may be a little different than yours. In my case:
- JJ 6CA7 vs EH 6CA7 vs Tong-Sol KT120
in the Rogue Cronus Magnum. I had the JJ 6CA7 in the amp for only a couple days then switched back to EH 6CA7 for a few days. I'm going swap the JJ 6CA7 back into the amp and listen to those for a few days. They DO sound good but my initial impression was that they were deep, richer, darker, not quite as detailed and softer up top. I'll give the JJ more break in time and see if my findings hold true.
And then there's the KT-120. I'm hesitant to go back to those as the 6CA7 tubes are sounding so nice!
.
~!
The Mind has No Firewall~ U.S. Army War College.
The manual says set EL34 bias between 25ma-50ma. As I can detect no significant difference in sound between 25ma and 50ma bias, I set them to roughly 25ma.I had a bad socket that was blowing tubes and I finally located and fixed that. I've had some tubes go bad in other sockets which I will attribute to the tubes themselves.
I now have a mixture of all sorts of tubes among the four survivors that seem to be lasting forever. I can't explain why some tubes last and others don't though. I'm happy with the sound even as I replaced all the small signal tubes throughout the chain which made a huge difference.
Edits: 02/23/23
Very good info, Thanks!
Since you can't get the KT120's. Lucky I have backups.
Please, What do you bias the JJ EL34II at in the CM II?
When I called Rogue, I was told 35mA, so the same as with the KT120s. But the fellow I spoke to was not Mark or Paul, and since then I've heard from some other CMII users who said that Mark recommends only 30mA and also says that EL34s won't last very long in the amp.So, I reset the bias to 30mA and I'll call back and ask for Mark to try to clarify all of this. It still sounds great at 30mA so for now I'm being cautious.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Edits: 02/23/23
Josh Thank You! I would go with what Mark has said. They are very responsive, but they should give all the bias settings to the various tube configurations The original CM was EL34 tubes based.
Nick was unequivocal, so the guy I spoke to last week was mistaken.I mentioned the name of the fellow who said 35mA just so Nick could correct him (not to get him in trouble!) and Nick said he'd speak to him just for future reference. So that's all good.
Nick also said that the EL34s likely won't last as long as KT120s or KT88s in the CMII, which doesn't surprise me. The JJ lineup is all so affordable, so I might replace the EL34s with JJ KT88s anyway, at least until new KT120s are available and affordable, if ever. Also, I just bought an ST-70, which should make the EL34s sing. :-)
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Edits: 02/23/23
Josh T.
When I had my Stereo 88 converted by Rogue into a Stereo 90 Magnum many years ago, Mark himself told me to bias EL34 and 6L6 and KT66 at 30 ma on the meter and KT88/KT90/KT120 at 35ma.
I never loved EL34 in the Rogue and I have a good collection of Mullard xf2. I actually like the JJ KT77 better in the Stereo 90, a pretty good sounding tube.
Now KT66 and 6L6GC, those are rocking tubes in the Rogue! Better than EL34 IMO, that's the tube you should try next. I like the GL reissue KT66 very much in my amp (much better than their KT88 which never sounded right to me despite all the love they get and I have 2 different quads) and of course the vintage GEC. Never tried the JJ KT66 but it's probably pretty good.
Enjoy the roll!
I've been curious about the KT66, and JJ makes one, including a blue glass version that's the same but looks cool, lol. They also make a 6550 and, of course, KT88.
What are your thoughts on the 6CA7 tube. I just bought a new build ST-70 with JJ 6CA7s and I love it. I'll probably try them in the CMII for the fun of it and see how the EL34IIs and 6AC7s sound in each amp. I will say I'm enjoying both amps right now (in different systems).
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
I have not tried the JJ 6CA7. The only JJ power tube I've tried is their KT77. I have tried the EH 6CA7 and it was ok in my Rogue, powerful sounding but lacking a little refinement. The JJ E83CC is a very good sounding 12ax7 variant if you can find it, not sure if they are still making them anymore. The only modern production small signal tube I have liked, although they can still be bested by the best NOS. The 12ax7 input tubes make the biggest difference in the sound of the Rogue amps as they have the greatest amplification factor. But they all make a difference.
Edits: 03/01/23
thanks for the info. Added to the potential replacement list. I kinda feel like I "settled" for Electro-Harmonix EL34s because they were readily available and relatively cheap at the time I needed to replace a set of winged Cs. I just can't chase winged Cs anymore.
I think Tube Depot does have Winged C EL34s, but they're well over $120 each. I'd give the JJs a listen given how cheap they are and how good they sound.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Holy cow! When I got the AudioPrism Debut in 1998* or so, it came with Svetlana EL-34s, which were generally no more than $20 each. At the same time, lightly-used late-production Mullard EL-34s were going for $100 each.Thank you for letting us know that the Winged C EL-34 is now $120 (!) each.
* That was when we were singing along to Shania Twain's "Still The One." Can't believe that was a quarter century ago. Sigh, getting old...
Edits: 02/21/23
Yep. My understanding, and it's likely not correct in all the details, is the following:The original Reflektor company went bankrupt in the early 2000s and the St. Petersburg factory closed as a result. That left New Sensor working with the Saratov factory as the only show in town for Russian made tubes. There was subsequent litigation over New Sensor's use of the "Svetlana" names and trademarks, including "Svetalana" "Svetlana Electronics Division" "SED" and "=C=." I think New Sensor mostly won the law suit, but may not use "SED" or "=C=" in the United States because their U.S. rights were assigned to someone else (but may use "Svetlana" in the U.S. and all associated trade names and trademarks elsewhere).
Hey, lawyers need to pay their mortgages too, LOL!
In any event, as a result of all that, the SED =C= tubes from the St. Petersburg factory haven't been made since the early 2000s and NOS has dwindled to a few here and there, which makes them expensive. (I bought seven low hour 6550s about a year and a half ago for $50 each and am very happy with them. It was a very good deal even then. I use them in a CJ Premier 11A.)
The good news is that New Sensor seems to have improved its QC at the Saratov factory in the last 20 years and their Svetlana labeled tubes are now quite good, as are their Tungsol, EH, GL, Mullard, etc., etc., tubes. I am willing to bet that the SED winged C tubes are partly so beloved because they're now NOS only and not necessarily because they continue to outperform the new Saratov stuff.
Unfortunately, PooPoo's decision last year to end the world as we knew it by invading Ukraine has resulted not only in death, destruction and suffering unprecedented in Europe since the 1940s, but also in unpredictable deliveries of Saratov tubes. So even staples like the KT120 and Russian made KT88s, 6550s and some EL34s are far more expensive than they were a year ago. If you can even get a KT120, for example, it'll be around $120 each (no one but New Sensor makes them). The Gold Lion branded tubes are also crazy expensive, while the other brands from the same factory are generally a lot less, but still quite a bit more than they were pre-invasion.
For me, Russia's invasion of Ukraine has made it very difficult to justify sending any money to any company that makes products in Russia. For tubes, that pretty much leaves JJ, China, or NOS.
The good news is that JJ makes some excellent tubes. I don't particularly like their 12AU7s, but I really like these EL34IIs, and I have been reading very good reviews on all of their power tubes, and they make KT90, KT88, 6550, KT77, EL34, 6C7A, KT66 and 6L6GC (and likely more). It seems that electric guitar players have loved JJ for quite some time and perhaps its reputation with audiophiles will go up now. We'll see.
But yes, crazy times and crazy prices.
P.S. I hope Western Electric finds a way to make some of these tubes, but that's a whole different kettle of wax.
P.P.S. I haven't tried Chinese tubes yet, for no reason in particular. I hear great things about the recent production PSVane tubes and will likely get some at some point soonish.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
Edits: 02/22/23 02/22/23 02/22/23
The new Telefunken reissues are also made in the JJ plant, to their own specifications.
I have no experience with them.
Jack
.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
My friends also had a Conrad-Johnson MV-55, which, like the AudioPrism Debut, used four EL-34 power tubes.
The Debut had a built-in meter, so you could try various bias points. AudioPrism recommended, but did not insist upon, 45mA. If you biased above that, in general, the sound became warmer and sweeter. If you biased below that, in general, the sound became more transparent and detailed.
The MV-55 had a scheme, where, for each EL-34, you backed off the bias, until the red light extinguished.
In the early-2000s, I know I was confused about the whole intellectual property issue behind the name "Svetlana."
Also, it just seemed that there'd always be abundant supply of affordable new tubes. We may not have realized that the years would fly by, current-production could fluctuate, and those taken-for-granted tubes from the late-1990s and early-2000s would become "NOS," along with NOS prices.
I still recall the hot and sunny days of Spring 1986, when I was a high school freshman. Back then, my friends were guys, not girls. Some of the guys played electric guitar and bass. They had heard that GE and Sylvania/Phillips were going to stop making 6CA7s and 6550s. One of my classmates claimed that Van Halen's Michael Anthony used GE 6550s in bass amps. But anyway, those friends wanted to stock up, but as kids, we could not afford things like vacuum tubes.
Who would have known that tubes from the early-2000s would be held in the same high regard?
How are JJ compared to old stock Mullard EL34?
This was my introduction to the EL34 tube so I can't compare it to others. But I am very pleased with it in my set up.
___
"If you are the owner of a new stereophonic system, this record will play with even more brilliant true-to-life fidelity. In short, you can purchase this record with no fear of its becoming obsolete in the future."
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