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Recent upgrade to Cronus Magnum

A few weeks ago, my system consisted of the following components ...
Apple TV >> Naim Unitiqute (v1) >> Harbeth P3esr

While I liked the overall sound, I wanted to move up the chain and try something different. I felt the Unitiqute was a little underpowered. So when an Audio Rogue Cronus Magnum came up for sale (local craigslist), I jumped at the chance and bought it. I had a Cambridge Audio Azure 851D stored in my close, which I added to the chain. So now my system looks like this...
Node 2i >> CA Azure 851D >> Cronus Mangum >> Harbeth P3ers

When I first made the change, I was quite impressed with the increased loudness and a wider soundstage. However, I realized that, unlike the Naim, I was getting listener fatigue. There was a certain harshness (like metallic sound) to the vocals, especially female vocalists. Also, I was expecting some tube magic, which frankly is just not there. The Cronus Mangum sounds much closer to a solid state. Yesterday I put the Naim back in the system and much to my surprise the little box is keeping pace with the much more powerful Cronus Magnum. Yes, it doesn't play as loud and the soundstage is not as wide, but the sound is so much more refined, smooth and balanced. I'm wondering if I made a mistake. So before I make further changes, maybe the good folks at Audiogon can provide some relief.

What do you think is the weak link in my system? Should I keep the Cronus Magnum and try a more musical, refined DAC? If yes, what do you guys suggest (prefer used, below $2000)? Or do I ditch the Cronus and go for a more tube-like sound (Primaluna, Rogers, vintage ARC, etc)? The little voice inside me is telling me to sell the Cronus and move up the Naim integrated chain (e.g. Supernait), since I really liked the Unitiqute's refinement and balance. But then again, what if it's not the amp (Cronus) but the DAC (CA Azure 851D) that's the likely culprit here? Should I change the DAC first? Or maybe try rolling different (smoother?) tubes?

As you can see, I'm mighty confused and can use some pointers. So many variables ... aargh!!!!
128x128arafiq
mod_asored
19 posts
 
I have a very similar setup
851N to Rogue Tempest
The Tempest is the next one up the chain but I think it is very similar. Now I have the Tempest 3 Super Magnum for what that is worth. I really like the 851N, however I am a modest guy just looking for great music.

I was looking for more of a "tube" sound, I loved the detail and punch of the unit but wanted more so I:1) Switched from Ultralinear to Triode mode2) Switched to KT-88 tubes (PSVane), I think this is a more musical tube than KT 90's or 120's3) Rolled my 12AX7 to a 5751 (Raytheon windmill getter)
Rolling to the 5751 had the most impact, this is a lower gain tube and I think it brings our more midrange detail and has a more natural tone than the stock 12ax7
Second biggest impact was the KT-88's, I did like the sound better, to my ears more musical and I don't really need the extra watts, my speakers are fairly efficient and my room is not huge.

Ultralinear to Triode, I think this helped, I found myself in much longer listening sessions once I did this.
Now I love it. I listen mostly to acoustic music. It works like a charm for me, I think the power output dropped from 90 watts to probably more like 30-40 watts but as the resolution, detail and tonality improved I found myself enjoying the music much more and also listening at lower volume levels.
Good Luck
avanti1960
1,474 posts
 
good info arafiq.
you have the CM II, it is an excellent amplifier that is neutral sounding but can be made more laid back with the right tubes etc.  you get a huge 3D sound stage and great dynamics with the KT 120 tubes and 100 watts. 
once you check the speaker terminals and adjust or confirm 8-ohms at the terminals-
1) check the tube bias for all 4 power tubes- once set it only needs to be checked every few months or so, mine never needed adjustment.
2) definitely no silver plated speaker cable.  i tried nordost and the sound was edgy and unrefined.   I use Kimber 8PR and the sound is smooth and excellent.   Very economical if you buy in bulk and make your own connections.  
3) defiitely no mullard !  everyone keeps saying mullard- i tried 3 diffeent ones and they all sounded dirty / unrefined in the lower treble.  here is my tube map for smooth success-

center preamp tube- (brent jessee)  screened for low noise (ask) 

12AU7 Amperex Bugle Boy type, Amperex Heerlen Holland factory code, blank label or Amperex white label or made for Dario, Philips, Adzam, Gulbranson, Eico, and others, original 1960s. New Old Stock original box and White Box. Very well made, low noise tubes. These are the originals from Holland, made in the same Heerlen factory , and at the same time as the Bugle Boy tubes, but labeled for other brands. Save big over the Bugle Boy label tubes and still get fantastic Bugle Boy quality!

49.00 single tube


front row 12AX7

RCA 5751 Premium industrial grade 12AX7, 2 mica

New Old Stock in white box, thick mica spacers. The best bargain going in a genuine NOS 5751, the RCA set the standard for all the other brands. MATCHED PAIRS ARE $110.00.

back row 12AU7

814A Premium industrial grade 12AU7, RCA JRC military TRIPLE MICA type, blackplate.

New Old Stock in original boxes. A really fine military grade triple mica blackplate of the 12AU7 family, made by RCA for the military. The early type triple mica blackplate 5814A of RCA tubes are very scarce, as they were not available to the general public, but are well worth the search. These are exactly the same electrical characteristics as the 12AU7 and can be used with improved results in any application calling for a 12AU7 or ECC82. Excellent quality that lasts. MATCHED PAIRS $99.00 PER PAIR

These changes will make the sound smooth and refined all day long and let you understand why people say it is such a great amplifier.  



kevinkoc64's avatar
kevinkoc64
30 posts
 
I hated the sound of my Rouge RP-5 out of the box, it was way more harsh sounding then my vintage ss Luxman preamp. And that's also a little true for the st-100 amp. I now run NOS tubes in both, Mullards and RCA tectonics for the preamp tubes, still using the kt-120s with much better results. And a power cord my not be a bad idea I use DH labs  you can try one from the cable company and if you don't like it you can send it back. O and by the way I also have the p3s just the 40th anniversary model.
 





 
avanti1960
1,474 posts
 
Yes the stock JJ small signal tubes can also sound unrefined.  They take forever to break in-  someone on another forum mentioned 700 hours to smooth out!  
arafiq's avatar
arafiq OP
1,664 posts
 
Alright folks, time for a quick update ...

I checked the impedance and it is indeed set to 8 ohms. Check.

I tried to lightly flick all the tubes and to my surprise, one of the front row tubes was wobbling too much. I took it out and inserted it back again, making sure it was a snug fit. Thanks for the suggestion.

But the biggest improvement came about when, as suggested by @davekayc, I removed the Cambridge Audio DAC from the chain and connected directly to the Node. It definitely took the harshness out in a noticeable way. Thanks for the suggestion.

@avanti1960  Thank you so much for the suggestions. I think I will start the tube rolling based on your recommendations starting next month. Please forgive my "nouveau-tube" ignorance, but are these tubes available at a website, or do I need to order from a dealer? If you can provide the sources I would truly appreciate it. Secondly, what's the better approach? Replace the tubes one at a time to measure incremental improvements, or go all out and replace all of 'em as you suggested? I'm really hoping that changing the tubes will have a meaningful impact.

@mod_asored, I'm not sure if the CM 2 supports the triode mode. I think v3 does but not the 2 doesn't. Feel free to correct me if I'm mistaken.
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