NAD M22- Benchmarking Target?

[JonMarsh]

I own an NAD M22, and from time to time follow reviews of this amplifier, including recently comparative reviews of the M22 and the Benchmark AHB2. Some of these reviews have favored the AHB2, some have called it a draw and sent back the AHB2, given the pricing and power differences. Most who have compared the M22 with a dual mono NC400 setup have preferred the M22, which could be due to a variety of factors, including the SMPS regulation, headroom, and front end design.


A key point of the M22 design is an adaptive input amplifier that controls the continuous clipping level, and regulates the amplifier to 250W continuous power rating (for IHF reasons, I'm sure) at 8 ohm and 4 ohms. OTOH, brief clipping power is allowed to be as high as the rails support, but it does still pre-clip the waveform, so that there is no loss of carrier frequency stability (when you clip a self oscillating CLASS D amp, the carrier frequency drops to the frequency of the audio signal- there is a frequency shift before and after the actual hard clip that produces audible spurious high frequency components, and it's quite desirable to suppress this, if one plans on running the amp up to clipping at all often).

You should be able to download the NAD white paper from my Public Dropbox folder:

https://dl.dropboxusercontent.com/u/7747441/NAD%20Masters%20Series%20-%20White%20Paper.pdf

It is my intention to do some extensive bench testing on my M22 once I get all the new equipment in- probably sometime in late January or February. I suspect it will be instructive. I'm also still hoping to see a review in Stereophile some day... but who knows, I may beat them to the punch!

[TEK]

I had no problem reading the document.
I see that NAD had eliminated the speaker relays and instead are using electronic protection - claming that to be faster and letting ledd power hit the speaker. Do you know if they have sdded a separet electronic minitor mechanism or are jusing the protection buildt into the ncore? ( I mean that I read somewhere that the nc500 has built in electronical protections that will sense dc current and set the amp in protection modus. The amp also, again if I recall correct, have built in shortcut protection).
If I remember right the plan were to find and use some high qualiry protection breakers. However, IF indeed NAD trust the ncore protection maybe that is good enough for us as well?
A big if there as I do not know what NAD does.

[JonMarsh]

Well, they are using relays with time delay circuitry SOMEWHERE because I hear them whenever I turn on the amplifier from standby mode. So, figuring out where and how is a priority.

I believe that as long as the module is working correctly, and no component has failed, the NCORE technique is good. But Stuff Happens, and it's for that reason I would consider putting in a speaker protection/disconnect relay. They would have to have complete disconnect of the output in some fashion (fuse?) to protect if an output MOSFET or driver failed, and fuses are distortions creators.

Let's consider this an issue to investigate. Also, this is something that can be handled by stuffing variations; that is, layout the board to handle using either option and different output connectors depending on how built.