Hypex N core module

The filter can do its job properly at current frequencies. There is an advantage to going to faster switching frequencies- lower distortion.

Sorry this is not correct, that is why when Stereophile do their bench tests they have to use a very special low power external steep filter on the output to get some good looking measurements from them.

Stereophiles: Audio Precision’s auxiliary AUX-0025 passive low-pass low power filter.

Trouble is that filter can’t be used at listening levels, as it would burn up in an instant.

Cheers George

If you look at the specs for a Merrill tarranis which uses an ncore module for class d output they show bandwidth to 50 kHz. If you look at the ps audio stellar 300 which uses an ice module and bandwidth to 50khz. The benchmark ahb2 is shown as a class ab/h not class d but class d efficiency and bandwidth shown to 200 kHz. The first watt f7 class a with bandwidth shown to 100k. All of these Amps are well regarded and carry the designers name and therefore affect his reputation. Is it possible that the difference is the difference in the voicing.... sonic signature that each designer intends based on their hearing and memory of music??

"if you want to have your product performing at the cutting edge it is not possible with today’s known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."

Several MHz isn't a problem. We're working with inexpensive devices that can easily do 5MHz and beyond. The problem is deadtime. That has so far proven to be the switching limit; that's why they don't switch much higher than maybe 2-5MHz tops. The deadtime increases distortion, and the faster you switch, the more you need it- so there is a minimum distortion that you can hit, sort of like Whack-A-Mole. I did state this in my previous post.

When you are switching that fast though, the speaker itself is part of the filter; there's no problem getting a filter to work and it won't burn up.

Here are the 10khz waves of Class-D both done by Stereophile tests, one with and one without the Stereophiles special AUX-0025 passive low-pass low power filter.  This filter can't be used while listening as it would burn out almost instantly.

With the special bench test filter:
https://www.stereophile.com/images/916BC600fig2.jpg

Without the special bench test filter:
https://www.stereophile.com/images/1212AM1fig02.jpg

Now I ask ANY linear amp manufacturer, would they be happy if their amp gave a 10khz square wave that looked like the second pic to sell to the public.

Cheers George   

Several MHz isn't a problem. We're working with inexpensive devices that can easily do 5MHz and beyond.

Technics have produced a Class-D amp (SE-R1) that has double today's switching frequency speed so the output filter has less of a chore to filter it all out, but it's $30k usd and special order only if your the God or Emperor of Japan?

This amp is half the way there because of the special hi speed semiconductors used to get double the switching frequency of 1.3mhZ

It's getting there, but needs to be double d again.

Here is one reviewers take on the Technics Reference SE-R1 Class-D amp:

" No other audio system that’s graced our listening room here at DT has captivated and mesmerised our staff quite like Technics Reference system. Seriously, some of us are having trouble getting our jobs done because we can’t peel ourselves away. This is the sort of audio system that you must hear to understand. Listening to tracks that we’ve heard 100s of times — and on excellent systems at that — is now a revelation of once hidden nuance and detail. Not only are we hearing things we’d never heard before, we’re hearing it in a way we’ve never heard it before."  

Cheers George