Expanding the Class D Conversation: How Would You Characterize Their Differences?

Not sure about that last question, but I have been reading about ROGUE and am curious if anyone has tried the Dragon? Apparently they have won some nice awards, commentary.

The Rogue approach includes a tube in the circuit – apparently, their designer found this was a way to avoid some of the negatives of designs without a tube.

These are negatives that – many here are saying – have been solved with the recent designs we've been discussing, but FWIW, here's another engineer's

 approach to this Class D design topic.

From Rogue: "Our proprietary tubeD circuit topology actually integrates the tube section into the amplifier yielding the smooth natural sound that only a tube amp can provide. With uncanny accuracy the Dragon Monoblocks deliver stunning dynamics and transparency without any of the edgy, etched, or grainy sound that often accompanies solid state designs.”

Another  Interesting interview, here, with Mark O'Brien: https://www.psaudio.com/blogs/copper/a-conversation-with-mark-o-brien-of-rogue-audio

O'Brien claims Rogue was the first high-end audio company to release a tube/Class D hybrid, back in 2011, when Class D "finally started sounding pretty good." The underlying logic is that a hybrid design offers the smoothness of tubes combined with the bass speed and accuracy of the best solid state.

He describes Rogue's proprietary "TubeD" circuit topology as one that integrates the tube section into the amplifier's output stage — not simply a tube circuit placed in front of a Class D output section (as with, say a tube preamp approach). "TubeD" employs a small amount of feedback from the tubes to create tube-like behavior in the Class D output modules, making the solid-state devices sound and test like large high-performance tube amps.

In another post I found, he described why he uses 12AU7 tubes. Apparently, it's because: he believes it sounds good and does an excellent job rejecting power supply noise while offering a low output impedance to the amplifier for proper signal transfer.

O'Brien's view about what makes or breaks Class D's reputation for "edginess":

"Another important aspect of this design is its use of large linear supplies for both the power amp and preamp sections. I'm a firm believer that the switching supplies used by many manufacturers are responsible for the 'edginess' detectable in some amp designs."

Source: https://everythingaudionetwork.blogspot.com/2014/03/audiophile-review-rogue-audio-pharaoh.html?m=1

"@audiobeatnik ...not tube-like but not the earlier Class D “thinness” that I have heard. It has more meat on the bone than my previous Class D experiences. Now we are getting somewhere!" 

PS Audio M1200 Mono amps (tube/ClassD):

A clip from an older article with comments regarding a front-end tube design as part of their Class D mono amps. These have been around for a while now too. How do they compare with others discussed here so far, who can chime in to add more?

https://theaudiobeatnik.com/review-ps-audio-m1200-monoblock-amplifier/?utm_source=chatgpt.com

@hilde45  I’ve been on a bit of a journey lately. A couple of years ago I bought a pair of Magnapan LRS+ and fell in love with their presentation. At the time I was using an AGD Tempo amp, and at anything above a pretty low level it strained to keep up. But I am aging with a bad back, so no class A behemoth for me. So I bought a Bryston 3B3 (AB), which had plenty of power but was a bit clinical. Then I bought a pair of Rogue Dragon Monoblocks. Closer! But fine tuning was crucial.

First, context: Aurender N200 > Denafrips T+ 15th > Backert Rhythm > Dragons > LRS+ (full range), KEF KC92 sub. 

First I replaced the Zavfino speaker cables with Silversmith Fidelium. Oooh! Then I replaced the PSVane Horizon 12AU7’s in my preamp with a pair of Ray’s Select 12AU7. Better yet! Then I replaced the JJ 12AU7’s in the Dragons with NOS Mazda 12AU7. Holly SH*T!!! 

Full bodied, gorgeous textures, air, incredible image depth and spacial separation. And not a hint of that upper midrange bump that I find so annoying. I’m a happy camper! Except maybe I need to get a pair of the X series Magnapans? (eye roll here).

The only other system that even came close in recent years was a Rogue RP-7 pre > Pass XA-25 > Spacial Audio X-5’s. But while engaging, it was a different kind of presentation and lacked the transparency of my current system. 

Your situation is obviously different with very efficient speakers. 

@markmuse  Interesting journey — the AGD Tempo struggling with the LRS+ makes sense given how power-hungry Magnepans are. Curious though: did you consider moving up to the AGD Audion mono blocks or higher rather than switching to the Rogue? The AGD Audion III mono blocks were pretty impressive.

How would you characterize the Rogue Dragons versus the AGD on a basic sonic level? I'm curious what the Dragons do differently, better, worse, etc. Since the system context changed, that might be hard to isolate, so "no opinion" might be the best answer you can give!

@hilde45 I did have a pair of Audion V1 prior to the Tempo. According to Alberto they are exactly the same except the Tempo channels share a common power supply. The Audions would have little more to offer. I did consider the AGD Duet monos, but they are twice the price of the Dragons and the Dragons were engineered specifically for this kind of a load. 

The Dragons are more robust sonically, if that makes sense. More physical. At first they seemed a little rolled off in the high frequencies, but the change of speaker cables took care of that. But the AGD amps have a little more emphasis on the upper mid and high frequencies, which they handle very well indeed. That is not to say the Dragons are not smooth or lacking in higher frequencies,.It is just a different presentation that I find a little hard to describe. 

As efficient as your speakers are either the Tempo or a pair of Audions would work very well. The only difference between the two would be slightly better channel separation with the Audion. Add a tube preamp and you will be in great shape.