Hypex N core module

     My opinion is that, for a thread that just asked if anyone had experience with Hypex class D amps, the numerous responses have instead provided a wealth of useful information from individuals that have experience with class D amps in general which has expanded the discussion well beyond just Hypex based amps and arguably was more informative to anyone considering a good class D amp. 
     I've enjoyed the discussion thus far and hope the OP, bache, feels the same even though the responses have expanded beyond his specific question. 
     The responses have been wide ranging, from class D is only good enough for subs, to class D is good but I think my class A or expensive class A/B or tube amp is better  to class D is very good and I sold my old amps.  I think these are all valid responses that are accurate and truthful with the exception of the first one.
     This thread has reinforced my opinion that exceptionally good system performance can be achieved with the use of the better class A, class A/B, tubed and class D amps.  I think the biggest benefit of class D is its efficiency and many might prefer an alternative sound for their systems. 
     I believe the better class D amps are so accurate and neutral that they may not be the proper amp for those who prefer a touch of flavor to their system sound that some of the better traditional amps possess.
     I understand the appeal of high quality traditional amps and would likely own one if my budget was higher. I like that everybody's system can be as unique as a snowflake and tailored to their preferences.

   Tim

Gentlemen,
If I may provide a designers perspective. I don't want to wade into a he said, she said. I am just providing my design experience.

Class D is going through a maturation stage and developing fast. The prior lack of experience in higher frequencies, above 20kHz, of Audio designers has led to some bad class D designs, while non-audiophiles have entered the market with good designs but bad Audio sound.

Audio sound, aside from being subjective (tubes vs SS), requires real time application and the human ear is very sensitive to sounds not just in the Audio range but outside it as well. Combined they make up the sound. The staging, "air" etc is also made up for many aspects that are not generally measure by Audio designers and manufacturers.

So with that Preamble.
Class D has suffered from lack of high frequency knowledge - designing traces that interacted with each other, designing power supplies that don't have kickback or noise, designing layouts that don't propagate RF, Capacitance in the MOSFETS that  don't allow fast switching (that is turning off from on, and on from off - this is not the switching frequency but speed on which it can respond),  Inductance of the MOSFETS cases, timing of the deadtime vs switch time and so on. While it is not very complex, Class D requires a lot more knowledge AND design then a Class A or Class B or a tube amp, only because there are a lot more complexities to be considered.

A good Class D will keep the dead time to a minimum, reduce interactions between traces and power supply ( overshoot, ring) and have a clean power supply so you don't hear it.   The amp boards and Power supply boards (Switching power supplies) are very sensitive to placement, wiring, components and so on.

Hence just making a amp board that sounds good is not enough. The whole amplifier has to be engineered. Switching frequency, theoretically is nice to have higher, does not work well with MOSFETS, as the capacitance in MOSFETS don't allow for a fast(er) turn off/on. 

The filters can be as clean or as horrible as the designer makes it to be. Having a sharp filter on paper with lossy components makes for bad sound as lossy components have a lot of parasitic impedance and will change the whole curve and filter.

Finally the Class D amps are of age where they can be superior to any other class available today - it just takes good design. Class D has many benefits that you cannot get from the other types of amps, including better sound. 

BUT as all things, there are no absolutes. It must be better design, better built, better implemented, better engineered to be better. Just saying Class D is better or worse does not make any sense as saying Tubes or SS is better then the other.

Hope that helps a bit with the understanding of Class D

Hi merrillaudio,

     Good information from an experienced and respected class D company (makers of the Veritas and Thor monos).  I agree that class D is still a maturing technology that  requires a complex design but has great promise.  
     I'm curious if you have any insight or thoughts on even further improvements in class D amp performance I've either heard discussed on audio forums or read about on more scientific sites:

1. Would higher switching frequencies benefit class D amp performance? 
     This is a topic which has mainly been propagated by one individual repeatedly not only here on Audiogon but on numerous other audio forums as well.   This theory states the current class D switching frequency (typically in the 500-600 Khz range) is too low and negatively affects  frequencies in the audible range.  I've had difficulty accepting this theory because I've never heard any evidence of this in any of my 3 class D amps, am unable to find any supporting scientific support for it and the only expert comment on switching frequencies I've been able to find thus far, from Hypex NCore and UcD inventor Bruno Putzeys, is that a 'reasonable switching frequency for a class D amplifier is just under 500 Khz or so, If you go much above that, you run into efficiency and headroom problems".  I'm trying to keep an open mind but was hoping you had some clarifying input on this matter.

2.  Will the use of eGan FETs be utilized in any upcoming class D power modules that you're aware of?

      These are the new Gallium Nitride FETs that switch on/off much faster than the current MOSFET transistors used in class D power modules.  If these switching output devices sound equally good or better than MOSFETS, it seems to me that could only benefit performance.  Just wondering if you know of any near future amps utilizing the new eGan FETs.

Thanks,
   Tim  

    

Anybody have experience with Nord Audio N-core power
amplifier ? The use own buffer module https://www.nordacoustics.co.uk/products 
and say the  Using Nord Input Buffer Boards (Full Specifications and Op Amp Sound) with high end discrete Sparkos Labs Voltage Regulators and a choice of Sparkos Labs SS3602 or the Sonic Imagery 994 discrete Op Amps both run in full Class A. And offers a richer, warmer, tonally dense musical sound with greater sound stage while maintaining all the benefits of the standard amp. Superb bass control with sweet high resolution mids and treble.

In what would be considered a "relatively affordable price range"...what is that then differentiates the Nord Acoustics from a PS Audio Stellar 300 from a Merrill Audio Taranas from a Benchmark ABH2 as they all have been given accolades for great sound at less than the price of a small car??