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In Reply to: RE: Update No. 1 on my EL34 recommendations post below posted by JoshT on February 21, 2023 at 07:19:19
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.
Follow Ups:
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!
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