No those aren't the links to the interview I mentioned but the first link above does summarize in rather layman's terms the reason GaN fets aren't much more than a marketing ploy in most cases when it comes to class d amps. Here is the relevant section (credit to the author, Bruno Putzeys):
"The Revolution that is, and isn’t GaN
New materials always get audiophiles’ hearts racing, much more so than strides in engineering fundamentals. Where would the loudspeaker market be without the perennial parade of new cone materials? They’d be forced to make fundamental improvements, which many people in the industry find challenging. Something similar is happening on the fringes of class D.
Let’s get this out of the way first: yes, GaN FETs are faster and easier to use than silicon. But at home audio power levels, the gap is narrow. 150V GaN FETs are about twice as fast as their much cheaper silicon counterparts. This means that if you drop GaN FETs into an existing class D amplifier, you can only hope to improve distortion by a factor of 2 or so.
But what’s a single-digit reduction, considering that in the past years, we’ve reduced distortion several thousand times using nothing but an extra op amp and a few passives (and, admittedly, reams of formulae)? Furthermore, that reduction goes across the board: distortion from switch timing, output inductor nonlinearity, and power supply noise are all impacted. Whereas the much-vaunted GaN FET improves timing distortion alone, which isn’t even that audible.
This explains why the established players haven’t jumped on the bandwagon. Head over to my competitors at ICE to read their excellent take8. The short rundown is: “When you know what you’re doing, GaN doesn’t really move the needle and is a waste of money. We’ll do GaN for you if you think it helps you sell products, but don’t expect any enthusiasm from us”. Amen.
By contrast, it’s been enthusiastically embraced as a band-aid and buzzword by parties who have little to bring to the table in terms of intelligent design or audio performance. The actual circuits in most commercial GaN-based amplifiers are nothing we wouldn’t have recognized 20 years ago. Often, they are basic open-loop schoolbook amplifiers, with lack of feedback ludicrously a claimed
benefit.
This is sad because GaN
is a breakthrough, just not one that’s relevant for Hi-Fi and home cinema amps. This changes markedly, and spectacularly so, once you pass 200V. 200V silicon FETs are significantly slower than 150V ones. By contrast, there’s not much of a speed gap between 150V and 600V GaN FETs. While GaN isn’t about to change what audio performance is available, it’s certainly going to change what power level this performance is available at. I can assure you, anything north of a kilowatt, I’d use GaN. Not because it’s magic, but because it’s practical. That’s something to look forward to. Imagine a touring amplifier with audiophile performance…"
