Thoughts about tubes and the Cronus Magnum II

Discussion in 'Audio Hardware' started by Lebowski, Oct 13, 2019.

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  1. Lebowski

    Lebowski Hey, careful man, there's a beverage here! Thread Starter

    Location:
    Greater Boston
    I've been looking at swapping my integrated amp lately. See some thoughts here on the Rega Brio-R and a few other models: Very surprised to not really like the Brio-R

    Yesterday I brought home a demo unit of the Cronus Magnum II. Dealer said they've had it for about two years, but it has relatively low hours. Not sure what to think of that.

    Anyhow, I'm a complete newb to full-on tube amps. I knew that tubes give off some heat, but wow, this thing gets really hot. I took our infrared thermometer from the kitchen and checked some of the tubes. Some of them were over 300 degrees F. Wow, I thought my HK990 ran hot but it's nothing compared to this!

    Firstly, I think it sounds really, really nice. Quite glorious actually. Very pleasantly surprised. However, for a piece of hi-fi gear this thing is noisy. The unit itself hums, and there's a hum coming from the speakers, and using the remote control to change volume results in a clicking noise through the speakers (experienced this previously in a Rogue Sphinx I used to have).

    I'm reading and getting reports of this being "normal." However I'm not sure we should be using the term "normal" for this; maybe "expected" is a better word to use? After all, aren't we looking to reduce if not eliminate noise from our gear? Why would noise be called normal?

    Do you have an amp with these kinds of noises? Can they be minimized? How much does one need to spend on a tube amp to eliminate them?

    And as for the temperature. It kind of worries me. My youngest is 6. She usually knows better than to touch the stereo, but things happen. (I am aware of the cage that Rogue makes)

    So, the amp sounds really nice but I'm not sure I can reconcile all the extraneous noises it makes. If it were only one of the three it would be easier, but I'm not sure. Am I missing something?

    Any thoughts?
     
  2. Helom

    Helom Forum member

    Location:
    U.S.
    About half of the integrateds I've had in my system exhibited some level of hum through the speakers and/or the transformer. I don't have the cleanest power coming in on my mains but power conditioners did nothing for the 4 Rogue products I've owned, each of which hummed/buzzed to some extent. I do find it very interesting that Rogue acts as though this is not typical, yet when they launch new versions of a product, a lower noise floor is often a touted improvement, i.e. the CMIII.

    In contrast to the CMII, my Cayin A88T is "dead" silent. It uses a toroid power transformer, the type of which are more affected by dirty mains. I bought the Cayin pre-owned for ~ $1600.

    I even tried lowering my mains voltage using a bucking transformer (thinking maybe the CMII wants voltage closer to 115 rather than my incoming 124) - didn't help any.

    Most of the time the noise didn't bother me as it was only obvious during sustained quiet passages, though I suppose it could hinder the amp's resolution capability.
     
    Joe Spivey and Lebowski like this.
  3. LARGERTHAN

    LARGERTHAN Forum Resident

    Location:
    Eire
    Personally, I couldn't reconcile audible hum with supposed high fidelity reproduction, no matter how sweet the sound. And moreover, not at that expense.

    Does the CM3 address these issues? This does seem a not uncommon complaint about the CM2.
     
    bever70 likes this.
  4. vinylontubes

    vinylontubes Forum Resident

    Location:
    Katy, TX
    My CM I had the remote chip upgrade, it still clicked after the upgrade. I think it's the from the motor turning the knob. Pretty sure the CMII include the remote chip upgrade, but if it doesn't it's relatively cheap and worth doing. It's a DIY project, just buy the $5 tool RA sells if you don't have one. My CM I does not hum at all. Dead silent except for the clicking with the remote. I'm powering Maggie 1.7 speakers. Again dead silent. The only tube I've replaced is the center tube. It's the one that is recommended to change of first. I bought a Platinum rated used Clear Top RCA to give it some solid bass and help out the highs. I liked it a lot. NOS clear tops are expensive. But you find used ones pretty cheap, especially if you aren't worried about matched pairs. Pre-amp tubes last a lot longer than power tubes, so I'm more than comfortable with using used tubes in the pre-amp section. When your power tubes go down, you will feel the pain of buying matched KT120s, though.

    Just a note on the Remote upgrade. The old chip was flawed with the acceleration of the volume. It would pick up speed the longer you held the button. So you would overshoot your desired volume adjustment (either too low or too high). If the volume transition seems linear, the chip has probably been upgraded.

    I will state that yeah those tubes get hot. Show your kid that it gets hot, kids will probably learn from your example. Otherwise get the cage. One thing I will state about the CM II is that I was never impressed by the improvements over the CM I. But the CM III looks like a huge improvement over CM III. So unless you are getting a super sweet deal on the demo unit, I would think about purchasing the new one even if you end up liking the CM II.

    Honestly, before you give up on the unit, call Rogue Audio for help with troubleshooting the hum. You don't get a helpdesk operator, you actually talk to the engineers. I think they are a really small operation and the don't get a lot of calls, or the engineers end up talking to the customers for help in the end. Regardless, there isn't a lot of bureaucracy you have to go through to get the right person to help you.
     
  5. Morbius

    Morbius Forum Resident

    Location:
    Brookline, MA
    Can't understand why a tube amp should be noisy at all. I owned an HH Scott 222C that was close to 50 years old when I sold it and even when I had the original tubes in it (Telefunken's) it was deathly quiet (no audible hum or hiss from a modest distance from my speakers). While I had that, I also had a Scott vacuum tube tuner and a tube multiplex adapter and except for over they air noise on weak stations they where as quiet the amp as well. For newer equipment I had a Jolida 502A and a Glow Amp One and both also didn't utter a peep. I've always used a powerline conditioner with all my stereo equipment though and it has always protected me from ground loops and any extraneous electrical noises so I think that may be some influence on noise levels.
     
    timind likes this.
  6. Lebowski

    Lebowski Hey, careful man, there's a beverage here! Thread Starter

    Location:
    Greater Boston
    So, just to verify: the entire unit gets warm, right? Like the chassis and knobs and what not? Earlier I asked my daughter (the 10 year old) to turn off the CMII and she remarked that the power button was pretty warm. And I noticed the knobs were warm before that.

    I'm a little puzzled by this whole tube thing. It sounds nice, but I feel like there's a nuclear reactor sitting in my living room!
     
  7. Balthazar

    Balthazar Forum Resident

    Owned a CM2 and heard no hum with any of the speakers I used it with, but none were more than 86dB. I've never experienced hum with any of my audio gear, though, so it's possible I lead a charmed life and am an outlier.

    It got warm, like most tube amps, so I sold it. I was using it in a small room and didn't have AC at the time. I don't recall the knobs getting warm. Just the top. Great amp, though. I wouldn't hesitate to recommend one to a friend.

    BTW, if you have a kid, just get a solid state amp unless you're able to corral your gear or fully trust the kids not to touch it. Better safe than sorry.
     
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  8. Synthfreek

    Synthfreek I’m a ray of sunshine & bastion of positivity

    I would not say that your experience is universal to “this whole tube thing.” The only part that gets hot on my amps are the tubes themselves.
     
    Lebowski likes this.
  9. action pact

    action pact Music Omnivore

    My '59 Fisher X-100 doesn't hum at all, and hiss is only audible when I dime the volume all the way to the max. Under normal listening conditions, it is utterly quiet. This is a 60-year-old amplifier; I would expect modern gear to be even quieter.

    Something is not right with this picture.

    None of the surfaces on my Fisher that my hand contacts to operate the amp are ever warm to the touch, just the tubes and transformers.
     
  10. Lebowski

    Lebowski Hey, careful man, there's a beverage here! Thread Starter

    Location:
    Greater Boston
    So I wonder if something’s up with this unit. It’s too bad because I think it sounds great but am now unlikely to purchase it, and I’d be leery of buying one online without testing it first.

    Maybe I’ll try calling Rogue.
     
  11. action pact

    action pact Music Omnivore

    I definitely would encourage you to continue checking out tube amps! It's hard to go back to solid state once you get used to what tubes have to offer.

    I still like my Rega Brio-R a lot, but after I re-tubed the Fisher and put it back into the system after a few months in storage, it was a glorious thing.
     
    Lebowski likes this.
  12. Lebowski

    Lebowski Hey, careful man, there's a beverage here! Thread Starter

    Location:
    Greater Boston
    And I’m guessing that you use it to heat your listening room during the winter months??? :winkgrin:

    You did mention something about seasonal rotation.
     
  13. action pact

    action pact Music Omnivore

    Absolutely, a tube amp will affect the ambient temperature in the room. Heck, the Fisher 400 I used to 0wn gave off a LOT of heat because it had twice as many tubes as the little X-100.

    I swap in the solid state Rega during the summer, because my house has no AC to combat the heat from the Fisher's tubes. It's a luxury to have two amps, and it also keeps things sounding fresh; tube and solid state amps have different strengths.
     
  14. No Static

    No Static Gain Rider

    Location:
    Heart of Dixie
    I have the CM I (about to upgrade to a III) as well as a Sphinx II. Both work great with any speaker I throw at them...currently Maggies and the Totem Model 1.

    I’m just sold on the Rogue sound as well as the way they do business.
     
  15. Lebowski

    Lebowski Hey, careful man, there's a beverage here! Thread Starter

    Location:
    Greater Boston
    I asked Rogue about this. They said if the unit is humming it could indicate a bridge rectifier is on the way out, or some type of environmental interference.
     
  16. mreeter

    mreeter Forum Resident

    Location:
    Kansas City
    I certainly don't have anything against Rogue Audio, I've owned a Cronus Magnum and a pair of M-180's Monoblocks, and their Customer Service is first rate.

    I feel like one of the reasons that Rogue can market their Amplifiers at a "Reasonable" price, is that they use inexpensive Transformers. The Transformers are the source of the noise, hum.

    I now have a pair of VAS Audio Citation II Monoblocks . They are an EL-34 based design that have large, hand wound Transformers, the Amps are dead quiet.
     
  17. Soundsense

    Soundsense Forum Resident

    Location:
    Colorado USA
    I had a CM I in the past for four years.....it was noisy and hot in all the ways you describe, including the phono. I sent it to Rogue and the noise was the same upon return and upon upgrading. I have not heard the CMII. I happily went sideways into a Quad 909/99 at the time.
     
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  18. Helom

    Helom Forum member

    Location:
    U.S.
    Weird stuff. After going through the full gamut of troubleshooting with Mark over the phone, he finally confessed that the power transformer hums because it's so large. Not once was a bridge rectifier mentioned.

    I didn't mention it earlier but I've owned the CMII twice and both units, manufactured years apart, hummed the same way. I thought the first example was likely just a lemon which is why I was willing to try another.

    I'd be surprised if they find anything "wrong" with your unit, and the answer is anything other than "could not duplicate."
     
  19. dolsey01

    dolsey01 Forum Resident

    Location:
    Boston, MA
    I've replaced the bridge rectifier on a different Rogue Amp and it was very easy. They sent the part and instructions. It took maybe 10 min. I've also done the remote control volume IC chip replacement, also super easy and maybe a 5 min job. I've had transform hum in multiple tube amps from different manufacturers but it never came through the speakers, just the mechanical noise of the transformer itself. I've tried the DC blockers and power filters and was never able to 100% eliminate it but it's definitely something in my power.
     
  20. patient_ot

    patient_ot Senior Member

    Location:
    USA
    Sounds like this thing really isn't for you. Probably time to take it back to the dealer.
     
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  21. Slippers-on

    Slippers-on Forum Resident

    Location:
    St.Louis Mo.
    I've had various tube amps in my life time without the issues of the CM1. Almost own the CM1 years ago until a AUDIO buddy in Texas gave me the skinny on his CM1. The last 13 years I've had hybrids with no hum or issues at all. But some audiophiles I really trust seem to have great success with the CM....build great rigs around them...and enjoy them for years, even touting how great they are over more expensive hybrids and straight tube amps. One such advocate is over at Audioasylum.com and I suggest you go over and chat with him about the CM1 if you are serious. I remember years agowhen he first got it he had issues with it until he found the correct set of tubes. So go over and chop it up with him to get answers if you are serioius about the CM1. He goes by the handle of AbeCollins and is the biggest CM apologist I know of.
     
  22. Slippers-on

    Slippers-on Forum Resident

    Location:
    St.Louis Mo.
    It's not hard to go back to SS....you just have to hear some awesome SS amps.....Ever heard a CODA amp?
     
    Helom likes this.
  23. action pact

    action pact Music Omnivore

    Point taken. I haven't heard very many high-end solid state amps.
     
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  24. Lebowski

    Lebowski Hey, careful man, there's a beverage here! Thread Starter

    Location:
    Greater Boston
    Any suggestions? I'm looking to spend less than $2,000.
     
  25. action pact

    action pact Music Omnivore

    I’m not very knowledgeable about modern tube amps, but I’m sure others will advise you.
     
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