New Class D amplifiers


Hello. I'm very interested in getting your opinion on the newer Class D amplifiers.  There has been a couple of very positive reviews (by Guttenberg) of the Bel Canto C6i and NAD M23.  These, and perhaps some others are offering new technology that significantly lower the class D noise level and other drawbacks.    

I currently use a Class A amp, Pass Labs INT-25 (with Dynaudio Heritage Special speakers) which has a wonderful sound. But I am transitioning to another location, and due to using Roon primarily I find that this system stays on most of the day.  Due to heat and power usage of Class A amplifiers, I'm interested in translating to Class D if I find something comparable.

128x128grantgg

@kuribo: Then, how do you account for why gallium nitride (GaN) FET transistors are being touted as "all the rage" among afficionados of Class-D amplifiers these days (witness the Stereophile review of the HiFi Rose RA180)?

Could you please cite one or more examples of those class-D amplifiers which you say are the "best performing class d amps on the market," and if possible, describe what kinds of silicon-based devices and/or alternative technologies their manufacturers are using instead. Thank you!

@erictal4075  have seen Rose but wasn't aware it was Class D.  Thought they were streaming Don't really care for steampunk look.

@tommylion 

Thanks for the input. Somehow Google didn't return a hit. At $5500 the AGD Tempos are at the same price as the Atmasphere, and on an earlier post @mglik mentioned his experience with the more expensive Audions vs Atmas as being different flavor rather than better/worse. This might suggest that at the same price point the Atmas might be better performers - but this of course is just pure speculation on my part.

As more units hit the market, I'm looking forward to getting more opinions about the GaN amps that take digital in and get a flavor if this elegant solution can be sonically on par with much more expensive implementations.

@erictal4075

See Bruno Putzey’s comments regarding GaN devices usage here:
 


As for better performing amps, see the new Hypex NCx, nilai500 and the Purifi amp modules.

GaN is the flavor of the day. Most of the amps using it are leaning on the marketing and claims of "new and improved". It’s only an improvement if you are clever enough to implement it in a way that exploits its advantages over traditional silicon and so far few are actually accomplishing that. In fact, many GaN amplifiers out, from Peachtree and LSA for example, use old class d designs without post filter feedback, resulting in load dependent frequency response. Most modern class d amps have post filter feedback and flat frequency response with load. Performance wise, load dependent response is a step backwards.

No rational reason whatsoever, from a performance standpoint, to spend $5000 and more for a class d amp. Of course if someone wants to spend $4000 for a flashy case to get performance that can be beaten by a $1000 Hypex or Purifi amp, it's their money to squander...

The advantage that GaNFETs have is they have very low parasitic inductance. What this means is its easier to build a module that is low noise- and by noise, I mean the kind that radiates from the module over the air and thru the AC power. Its important to keep switching noise and parasitic noise low because it can mess with other gear and affect its performance. As an example, our class D amp makes less noise on the AC line than most tube amps. In terms of noise that it makes in the loudspeaker itself, 90% of that comes from the input buffer circuit, but even then is obviously quieter than tube amplifiers (I use horns at home FWIW).

We've been docked a bit on account of the cost of our class D (which is cheaper than most of our tube products). We built it to be rugged (so it will ship without damage), to last decades, to be easily repaired and updated and to that end it has a fairly expensive chassis and power supply. It would actually be more expensive if we used someone else's module.