Amps for B&W 805 Diamond: Rogue Audio or Krell, Pass labs, ML, Accuphase

The Medusa is a great amp with outstanding detail and 3D imaging/soundstage but I wouldn’t recommend it for the 805s unless you’re willing to do some tube rolling so of the two I’d side with the Krell.  With Pass I’d go with their XA series as it’ll likely play nicer with the diamond tweeter.  The Plinius SA103 is also a great choice, and it has a hi/low bias switch so despite being fully Class A you can leave it powered on or use it for less critical listening purposes without the amp running so hot.  Last recommendation would be the Clayton Audio S100, and if I had the 805s that would be my first choice.  Hope this helps and best of luck. 

Thx soix for your advice a lot. May I ask in detail why Medusa might not suitable for B&W. Rogue Audio is very good for bass so I suppose it is ok with B&W, isn’t it?

The Medusa, while being an excellent amp, definitely leans to the more detailed/revealing end of the sonic spectrum (at least with the stock tubes) and I’d be concerned that this combined with the 805’s likewise very detailed diamond tweeter might make the sound come off as a bit overly bright sounding and potentially fatiguing on extended listening. If you can share what sound characteristics are most important to you and what improvements you’re looking for it would be very helpful in making recommendations better suited to your specific tastes. BTW, what amp are you using now and what’s the rest of the equipment in your system (including interconnects, speaker cables, power cords/conditioning) and what are your listening room dimensions?  The more info you give here the better the recommendations here will be. 

My type of music are quite variety from slow music like pop ballad, country to soft rock like The Eagles. 

My most important sound characteristics are deep, soft, neat bass. Also a thick, warm mid-low and sparkling treble.

My systems include Dac Chord QuTest, NAD M3 amplifier, 805 Diamond, Sub Rel S510. Speaker cable is Ansuz X

My room is ~ 20m2 but it's a living room so sometimes I must open small volume but I still need the detail with that kind of volume.

Hope to have your reply soon, & thx for your very generous advices

My most important sound characteristics are deep, soft, neat bass. Also a thick, warm mid-low and sparkling treble.

The only thing the Medusa will do well for you is the sparkling treble as its mids are not thick/meaty (although not thin) and the bass is about as tight and quick as any amp I’ve had in my system and nowhere near soft sounding. 
 

I don’t know if you’d have access to this used and fully-upgraded McCormack amp wherever you’re located, but given what you’re looking for I’d be all over this incredible amp because I think it absolutely nails the sound profile you’re looking for and is being offered at a very fair price.   I have the same amp at SMcAudio getting very similar upgrades now and can’t wait to get it back because with Steve’s upgrades these amps are thought to be at a near SOTA level. 
https://www.usaudiomart.com/details/649875150-smc-audio-modified-mccormack-dna-5-ultra-mod-with-gravity-base/

Or there are the other amps I mentioned before that I think would also be excellent except maybe not as much sparkling treble.  Other amps you might look into are Belles and Parasound.  Hope this helps. 

Thx Soix so much for your rich expertise. Unfortunately, in my country, only Krell, Mcintosh, Passlabs, Rogue Audio, Plinius are available. Would you mind share the sound difference for each of those.

@truongv0ky I ran B&W N803 with Pass XA250.5 and Audio Research LS-25 preamp. Great combo. The XA series would work well with the 805s.
I think the sound you’re looking for you’ll find with Pass XA-30.8. 
I had Rogue separates (ST-100 and RP-5) and while very good the Rogue stuff tends to lean slightly towards dry sound in my opinion. 
Also, your Chord Qutest will be a good match with Pass Labs gear.
The Qutest has great tone and it won’t be masked or veiled by the Pass amp.

Well, I’d rule out the Medusa for previously mentioned reasons, and I’d rule out McIntosh because the treble will likely be too reserved for your tastes.  I’m not familiar enough with Krell as they seem to have shifted back to their more classic sound, which is a good thing so worth exploring.  If looking at Pass I think the X150 would be the one to focus on as the XA series might be a little too soft in the treble for your tastes.  The one that intrigues me is the Plinius P10 that is considerably cheaper than the others but seems to exhibit sound characteristics that are close inline with what you’re looking for.  This review may be of interest to you…

https://www.whathifi.com/plinius/p10/review

Thats all I got for now, and I’d encourage you to read as many reviews as you can on these three amps to see if one seems better suited to what you’re looking for than the others. 

McIntosh pairs excellently with the B&W diamonds.  The newer Macs are not reserved or rolled off but smooth enough to give your speakers the ultimate in resolution with none of the excessive artificial brightness.  Heard this pairing many times and also Mac with even brighter speakers like Klipsch Heritage and they sounded like a winner every time.  Mac and Harbeth? Not so much but with the diamonds the system shines.  

Thx @soix ​​​​@audphile1. I’m doing the research for those.

Thx @avanti1960, what model of McIntosh will be suitable for 805 Diamond?? I am also looking for the hybrid ones such as MA252 or the solid ones such as 6600, 6800, 6900, 7000, but do we need to stay away from the ones that are too old (more than 30 years old)

@truongv0ky 

Buy as new as possible- 10 years old max.  The hybrid amps (252, 352) sound excellent and do work well with the 805d.  I would avoid their entry level amplifier.   

I have owned both a Mc MA252 and currently a MA 352 in which I have used with a pair of Bowers 805S models and they seem like the perfect match in both tonality and detail. Right now for fun I’m running my MA352 with a pair of Klipsch Heresy IV’s and like the previous post above, the McIntosh is not bright and other than having a ton of headroom due the the Mc’s power, it is very satisfying and non fatiguing. 

Have to disagree with @soix here. 
The Pass Labs XA series is more refined than the X series. Let’s not confuse refined treble with softness. I’ve owned both X and XA. There is no softness in the treble region with the XA30.8. It breathes life, details and tons of air into the music. The midrange on the XA is absolutely clear with zero glare. Bass is big, deep and plush. A welcome trait for the 805D. 
At the end of the day, you can’t go wrong with either the X or XA series. Pass amps kick butt with B&Ws. 
McIntosh newest stuff should work well too. Their new integrated amps are very good. 

truongv0ky

The Accuphase would make a very nice match. Good advice above as well.

Happy Listening!

I completely defer to @audphile1 as nothing beats actual personal experience, and I stand corrected. 

@soix 👍 

Something else to add…

One downside with Pass labs gear, if you can consider it so, is the fact that it takes about an hour minimum for their components to warm up and perform at their peak. It isn’t exclusive to pass however in the case of XA with pure Class A operation you’re looking at 380w power consumption at idle. I never measured how much the XA30.8 amp actually pulls from the wall during normal listening but I’m pretty sure it isn’t shy. If that’s a concern then opt for Class A/B X series. Slightly more efficient. As far as heat, the XA gets warm but won’t be a space heater. It’s more than tolerable. Hope this additional information helps as well. 
 

@audphile1 If it takes 1 hour to warm up a class A Pass Lab amplifier so it will be a problem for many persons. This issue only happens with Pass or for any other class A of other brands?

@buckheadmac Yeah, I know the MA252 is very good but it is only 100W. Is it enough for 805 Diamond? Normally I see people use 150W or more amplifier?

@jafant which one would u suggest. E530, E550, etc..? I know that Accuphase sound very good but I'm only afraid that Accuphase is hard to bring the liveliness and joyful of the song to us

truongv0ky

Audition several Accuphase models as possible.

Stay in the 50 Series, 550 or 650. Believe me a Joyful song will be appreciated and enjoyed.  Keep me posted on your demo sessions.

Happy Listening!

@truongv0ky it’s pretty common for any component to take some time to start sounding its best after it’s on and out of standby. It will sound just fine when it’s cold but will get even better after about an hour is what I’m saying. It isn’t proprietary to Pass Labs gear and I wouldn’t classify this as a problem. 

Thx all you guys for very supportive advise

Yeah, I know the MA252 is very good but it is only 100W. Is it enough for 805 Diamond? Normally I see people use 150W or more amplifier?

@truongv0ky I own a pair of the way earlier B&W 805 Matrix speakers, and I do not know if they are a similar load to drive as the 805 Diamonds are (from memory I believe mine have an efficiency rating of 87dB, a nominal impedance of eight ohms), but I am currently driving them with a Cary amp that is switchable between 50 watts/triode and 100 watts/ultralinear and I honestly prefer the triode alternative. However, one of the rooms I have used to listen in is on the small side of medium and the other is positively small.