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New Bel Canto REF600M using NCORE

Wow!!..Looks like John hit another home run at Bel Canto with the just released REF 600M using NCORE amplifiers. 300 watts into 8ohms. $4500.00 a pair. The REF 1000M is out of production. I have a feeling this is Bel Canto's best amp ever below the Bel Canto Black. Look forward to Guido checking it out.
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georgehifi's avatar
georgehifi
10,312 posts
 

I listened to a promo pair of these a few months ago, and I was finally impressed with the sound of Class D.
But they were driving expensive two ways with an easy load, and in particular the ribbon tweeter was a nice flat 6ohm load impedance and flat small negative phase angle, which can to my ears make Class D sound not so good if it wanders too much in impedance and phase angle. So I wasn't sold, and have no opportunity to hear them on something more taxing to Class D. in the HF
 
From what I gather they do stray from just the off the shelf NCore design, as I believe that Belcanto have do their own output filtering which is tricky, and from what I gather it's a few series up filters so they can still push the power though them without blowing them, yet get a sharper rolloff to get that nasty switching noise killed off without effecting the audio band too much. But then series'ing up filters has it own set of problems, eg ringing again?? At least their trying.

Still to me the best way is to increase the switching frequency at least 5-10 times higher than what technology can do now. Then in the future when the technology allows this to happen,  just a single filter will do the job of killing the switching frequency noise without it's artifacts being anywhere near the audio band. 

Cheers George   
rampage60
23 posts
 
I currently have a pair of Pass Labs XA160.5s and my speakers are Martin Logan Summit Xs. How would the REF600M compare to the XA160.5s. Would be nice to have cooler running amps. I don't want to sacrifice the SQ.
georgehifi's avatar
georgehifi
10,312 posts
 
rampage60
I would stick with the XA160.5's as the ML's like all of them go down to 1ohm in the HF and this is where Class D has real problems.

Cheers George
blang11's avatar
blang11
37 posts
 

Steven Stone reviews the Ref 600m in the January issue of the Absolute Sound. In his conclusion, he states, “To my ears, it is good enough to qualify as the best all-around power amplifier I’ve heard to date, regardless of technology or circuit topology.” Chalk up another win for Bel Canto!


While Mr. Stone does not dwell on it, he does note, “ With the Ref600M powered up I could hear only the faintest hiss if I put my ears within a few inches of the Spatial’s coaxial driver [his review speaker]”. He later compares his recently refurbished Pass Labs X150.3. “After its return from the factory, the Pass was almost as quiet in terms of noise (without a signal) as the Ref600M, with only a slightly higher hiss level and zero hum.”


I find this very interesting. How common is this hiss/hum issue? Is it caused by class D topology? Seems not, given the reviewer experiences this even with his class A/B Pass amp. And is this issue caused by every product of a certain design or does it depend on what other components are in your system? All three of the class A/B amps I’ve previously owned were completely silent when powered on but playing no music. Putting my ear to the speakers revealed zero sound. Then I got my current Audio Research DSi200 integrated amp (class D) and it does produce a faint hiss from the tweeters and low level hum from the woofers of my Revel F208s. Close up, it is easily heard, but it’s faint enough that it can’t be heard from any further than a couple feet away, even in a silent room.


I don’t feel this hiss/hum thing is a deal breaker. My current system plays music very well. But ideally, I would never experience hiss at all.



mapman's avatar
mapman
21,948 posts
 
No hiss or hum with my Bel Canto ref1000m or C5i. In fact noise floor is lowest I have heard.  
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