When I experienced issues it was with the stock reissue JJ's installed (not that I'm necessarily 100 % sure they are the culprit), for what it's worth. Hasn't occurred since rolling any of the old tubes.
Hi all: Fairly new Cronus magnum ii owner here (about a year in). Also have KEF LS50 speakers and a Clearaudio Concept with Satisfy tonearm and a Performer V2 cartridge. Love this set up, but am ready to take the next step with tube rolling. There's a lot of great advice in this thread, but have to admit it's a bit hard to know where to go for all of this stuff. I'd like to spend around $300 bucks to upgrade all of the preamp tubes. Anyone have a good suggestion as to how to spread out that budget to get improved sound? Bonus points for actual links to where I can buy this stuff. Also - with my KEF LS50 speakers, should I have the amp set to 8 ohms or 4 ohms? Seems like conflicting info is out there. Thanks!
If you don't mind popping the top and doing the work to change the setting, try it both ways and see which you prefer. There's not really an exact answer here....just depends a little on what sound you personally prefer.
There are many, many people who insist that a NOS Mullard is the way to go for the center tube. From what I have read it is a warm sounding tube with quite the mid-range bloom. People don't seem to get to finicky about the rest and leave the JJs gold pins as they're pretty quiet and reliable. Personally, I went with a new production Genalex Gold Lion. It is a very good and quiet tube with a linear sound profile. It's best attribute in the CM is that it added more depth to the soundstage. It does take about 20 hours of burn-in before you can expect an idea of what it will sound like. At first it was a mid-range beast with walloping tubby bass and rolled off highs. Regarding 4 or 8 ohms; I think the 8 ohm taps present a leaner clear sound. It always made me think of water and swimming. The 4 ohm taps added deeper bass with more slam. Upscale Audio is a very trusted place to purchase NOS and new tubes. You will be able to find better prices but they also offer top notch customer service and quality control. They also have rolled a lot of different tubes and combinations in the CM. They're great with an email or phone call. I hope that helps some.
Just changing the 12Au7 in the center is the best bang for buck swap. You might also get a pair of 12AX7. I would not bother fretting over old stuff. If you want that, call Brent Jesse and ask for his suggestions for those tube types in those positions. There's a place in DC that has a lot of weird tube gear and should have that stuff in stock if you can get in and geek out over it with whoever is there. Personally, I'd stick with what you have or I'd get the Gold Lion versions of the tubes I suggested, to see if you like that presentation better. There isn't a "one and done" or a "night and day" type of replacement. They all have the same basic specs, so changes will be more subtle than what you might expect. -Bill
Both, Upscale Audio and Brent Jesse Recording & Supply Inc. are great. I'm a CM III owner and have been very pleased with the improvements I've experienced replacing the stock JJ's with Gold Lions in the 12 AX7 spots, Amperex Orange Globes as the 12 AU7 drivers and a 1956 LP NOS Mullard in the center position. Good luck and enjoy!
Well, long post ahead, but I hope I can find some help here with my amp. First, the good news. Out of the possible tube combinations I have now, The Brimar 12Au7 in the centre accented by the combination recommended earlier in the thread (GE 12AX7 ECC83 Long Plates and RCA 5963 Black Plate 12AU7's) has been my favourite suite of tubes. The sound is absolutely fantastic. Previously, I was finding the Brimar wasn't playing nicely using the stock JJ 12AX7's. By comparison, I definitely preferred the Radiotechnique 12AU7 in the centre. This sounded pretty good with the JJ's, although it veered towards somewhat bright IMO. Once I added the GE's however, I found the overall sound to get bassier (arguably good), but also noisier and just a little less defined. Relatively subtle, but enough for me to think it could be improved upon. I switched the Radiotechnique back to the Brimar and was completely floored. Clarity, soundstage, bass, etc. all sounding absolutely beautiful and experienced no amp issues while listening. Now for the bad news: As a brief background, we'll rewind to a few days before. I've been tube rolling my preamp tubes over the past few weeks without much issue. In one case, it appeared I didn't seat one of the tubes perfectly so the filaments weren't lighting up. I reseated it again and it appeared to work without issue. That being said, I have noticed that some of these older tubes have a harder time being inserted in the amp and staying in tightly. Fully welcome to admit if this is purely my incompetence, but nonetheless, this issue came to a head when I abruptly hit my elbow on the table (although very lightly) while the amp was on. This slight vibration managed to dislodge two of the tubes (right 12AX7 and right 12AU7). This resulted in buzzing, etc. and I quickly turned the amp off. This hasn't happened to me in the past. Is it possible this caused issues? I powered down and reseated the tubes and all appeared fine. At this point it was the Radiotechnique, RCAs, and GE's installed in the amp for what it's worth. Switched the Brimar back in which led to the positive impressions above, etc. Back to the present-I turned the amp on yesterday morning and the sound coming out of the amp appeared to be microphonic tubes (I had experienced nothing like this the evening before). Loud humming which was then exacerbated by touching the amp, slightly tapping tubes, or even the table itself. The kicker being I'm not even sure which tubes were necessarily the culprit(s) here. Nor have I experienced this sound prior. Is it possible the tubes became microphonic this quickly? The NOS RCA's and GE's were from Ebay, albeit both 100 % sellers, so I wasn't necessarily concerned, but trying to think of all possibilities. Based on this, I decided to revert the tubes to the previous Radiotechnique, RCAs, and JJ 12AX7's combination. This removed the loud microphonic sound, although now I was noticing some crackling coming out of the right speaker. Thinking this was perhaps a sign of power tubes nearing the end of their life/failing, I installed the new Tung-Sol KT120's I got. Now, I didn't notice a crackling, but did notice a loud-ish pop when amp was exiting the warmup mode, as well as about 10 minutes after it turned on. Decided to turn the amp off and leave it for now. Throughout all of this, my volume knob was set to 0 and issues occurred irrespective of inputs. Any help is very much appreciated. Sorry if any portion was confusing. Happy to clarify any point if needed! I'm trying to decide between throwing up my hands and getting the amp into the shop ASAP or to continue trying to troubleshoot issue(s). Hoping I haven't in any way damaged my amp and this is purely user incompetence! Very much enjoyed the *one* evening I had listening to the Brimar/GE/RCA combo though.
How loud was the crackling? Mine has always done a tiny bit, albeit relatively quiet, during the first few minutes while the amp is warming up. If what your experiencing is the same thing; it's fine and normal. I would also reach out Rogue. They have great customer service. An email usually gets a reply within a few hours. You can also call them.
Pretty quiet (lower than conversation level), although I haven't experienced this crackling before. And yeah, can't hurt to reach out to Rogue, I suppose. Cheers.
Could be the tension on the clips in the tube sockets is beginning to loosen do to the constant insertion and removal of tubes. You no longer have good contacts and they're sensitive to vibration. Also on newer tube amps the tube sockets are soldered directly to the PCB which are flexing under the pressure of removing and inserting tubes this also causes the copper traces on the PCB to flex and eventually crack producing intermittent or even open circuits which can produce crackling or other noises and eventually cause the circuit to go dead. This also puts stress on the lands on the PCB that the leads of the tube sockets are soldered to causing them to lift and become unattached to the PCB, again producing the chance of an open circuit.
Thanks for the insight, although somewhat concerning if true. I've only changed tubes on the amp a handful of times in the past 2 years so I'd still imagine that is relatively low for the issues you mentioned.
rogue tube sockets and connections have been rock solid for me, they deserve a complimentary e mail imho. i have wailed on them over the years in the three rogue products i have owned and still own. i have a drawer full of NOS tubes to prove it. very well designed and made. i wish tubes were as solidly made.
Glad to hear. I was hoping you and some of the other Rogue owners might chime in! I did go ahead and email them. My only concern is if it *is* the fault of the tubes, then I would like to return them within the return window versus sit on this issue for weeks. For what it's worth, I did not experience any issues until I installed the GE 12AX7's in the amp, though hard to say if it's the culprit 100 %.
Wondering why enjoythemusic.com just published a review of the "new" Cronus Magnum II when the III has been out for quite a while?
So, Rogue's suggestion to take off the cover and reseat the tubes was helpful. I felt I applied enough effort previously, but guess it wasn't enough on one or two of them and a little easier to see. The aforementioned issues are gone, but now I'm noticing a slight buzzing in the left speaker that isn't present in the right, irrespective of volume. Hmm, the fun never ends! Thanks again for the help and suggestions here.
For all the tube amp owners (i own CMII) this is an extremely helpful link. Mr. Jim McShane knows what he is talking about.. "Tube Problems" That Aren't Tube Problems - Jim McShane - Tubes Asylum
Thanks for the link, Theron. I was considering picking up cleaning-related stuff for tubes so this is a great help. I'll be very happy if these issues are purely my error, and not faulty gear Also, the buzzing is so minute upon inspection an hour later that I'm wondering if it wasn't there before. Will certainly give the D5 a go when it arrives.
Still I find that my SS amps just work, are quiet and continue on working. My my tube amps have tubes that fail, become noisy and wear out. You can love the sound of tube amps but they will always come with overhead.
Honestly, any tube related problems I've had with my RCM have been minor and infrequent over the last decade. Don't regret owning a Rogue tube amp at all!
So I've reseated the tubes again and still dealing with what sounds like noisy tubes. The amp turns on quiet, and within 2-3 minutes a microphonic hum begins. All tubes appear to be seated properly, filaments lighting up normally, etc. Hmm.
