Greetings friends, I hope you are doing well! 🙂

Above photo: Infineon GaN Class D amplifier connected to a Leben RS-100 vacuum tube line preamplifier in my A-V system. 

Yesterday, after its arrival, I got Jun-san's Infineon GaN Class D amp installed in my vintage Altec A5 Voice of the Theatre loudspeakers-based audio-visual system. I powered it up for a little listening, and sent Jun-san a message inquiring about how long I should run-in the amp for its full performance to develop. 

Typically, I consider run-in for audio components to be about 100 hours before they fully stabilize to reach their full performance level, but for some components I've found it can take much longer than that. 

Jun-san replied and said, "In my experience, it takes 3 days for the amplifier to fully settle after it has been moved. This process likely involves some mechanical settling, as the amplifier does not need to be powered on the entire time. The bare minimum warm-up time is 30 minutes, as the sound can initially be a bit dry and thin."

Above photo: my vintage Altec A5 Voice of the Theatre loudspeakers based audio-visual system.

Jun-san's recommendation has been my experience with completely run-in audio electronics. If you take a component in and out of an audio system it seems that it takes a while for everything to settle back down for full performance to emerge again, which of course means quick A-B comparisons aren't really very meaningful.

A better approach is to let a component play music until it reaches its baseline for full performance, and then listen to a wide variety of source material over a longer period to get an idea of what it is about performance-wise.

I listened to the Infineon GaN amp before it warmed up for a while, watching some TV shows, and I concur, it did sound a bit dry and thin initially, just as Jun-san had said.

After it had warmed up for a while, maybe a couple of hours - but way before Jun-san's recommended 3-day settling-in period - the amplifier dramatically transformed. The sound quality became rich, liquid, natural, detailed, dynamic, very transparent, with vivid visuospatial effects, including an enormous sense of recorded space. Whoa!

Photo above: Jun-san's demo Infineon GaN Class D amplifier. 

Indeed, the Infineon GaN Class D amplifier sounded very, very, impressive, and very "SET-like" in the very best sense of that kind of performance. Except the Infineon GaN Class D amplifier is a 100-watt per channel "SET" on my 16-ohm A5 loudspeakers, which makes it all the more intriguing.  

I could definitely hear why the Infineon GaN Class D amplifier made such a huge positive impression on attendees at the  “OTOTEN 2026” HiFi festival in Tokyo, including our friend Yazaki-san.  

As I listened I was reminded of Yazaki-san's statement, "I believe Infineon's GaN Class D technology will likely be regarded by future generations as a landmark development in the century-long history of amplifiers."

Above photo: the latest issue of the prestigious MJ Audio Technology magazine from Japan covering the Infineon GaN Class D debut at Ototen 2026 in Tokyo.

When I posted to my Facebook pals about the extensive and enthusiastic coverage that MJ Audio Technology lavished upon the Infineon GaN Class D amplifier after the Ototen 2026 HiFi Festival in Tokyo, and Yazaki-san's reaction, my esteemed audio pal Bruce Berman commented: 

 "Jeff, as much as I am a long-time advocate and enthusiast for SE DHT amplifiers, I recognize the technology, while very musical to listen to, will someday be replaced by class D amplifiers. It's only a matter of time until the technology becomes perfected to the point that we begin replacing our beloved SE DHT amplifiers with class D units."

I was shocked by Bruce's comment, as Bruce builds some of the most impressive SET amplifiers you're ever likely to see, and because of the comment, at least one reader thought Bruce's Facebook account had been hacked by an imposter - it wasn't! 

Photo above: Jun-san's demo Infineon GaN Class D amplifier. 

Both Yazaki-san's and Bruce's comments were rolling around in my head as I was listening to Jun-san's demo Infineon GaN Class D amplifier, and I thought, "Yazaki-san and Bruce may very well be right." 

I'm very impressed with what I'm hearing from Infineon's GaN Class D technology. The appearance of the Infineon GaN Class D amplifier may indeed mark a significant development "... in the century-long history of amplifiers," just as Yazaki-san has said. 

As I was listening to Jun-san's Infineon GaN Class D demo amplifier while watching TV, a show about dinosaurs, in my imagination I was thinking about the Cretaceous–Paleogene (K–Pg) extinction event caused by a huge asteroid impact on Planet Earth that occurred about 66 million years ago, which wiped out all of the non-avian dinosaurs.  

Could the Infineon GaN Class D amplifier be that audio amplifier "asteroid" that wipes out most other amplifier "dinosaurs" on Planet Earth? I don't know. Maybe?

Last night as I lay in bed dreaming, I heard a loud bell tolling, and when I woke I wondered if that was my subconscious reaction to hearing Jun-san's demo Infineon GaN Class D amplifier. Was that bell tolling signaling the beginning of the end for the amplifier designs of the last 100 years?  Was a new era of GaN Class D SET-like amplifiers emerging that would become the new reference "SET-like" standard? 

Yesterday, I posted on Facebook for my audio pals, "What happens when a $77 billion dollar company - Infineon - decides it wants to make a statement in GaN Class D amplifiers, and it's designer - Jun Honda, an audiophile, a friend of Yazaki-san's - who has been developing the design for over 20 years, sends yours truly the latest version that he hand built, to demonstrate what it can do?"

Above photo: Jun-san's Infineon GaN Class D demo amplifier - I want one! 

Well, now I have a partial answer to that question. Of course, I've got a lot more running-in, listening, and comparisons to do before reaching any firm conclusions, but it is clear the Infineon GaN Class D amplifier that Jun-san built is a very impressive amplifier indeed.

I'm looking at the amplifier, and thinking that Jun-san's build of this Infineon GaN Class D demo amplifier is not exotic in terms of circuit components, and that this is the sort of amplifier a DIY'er could build on their kitchen table for a relatively modest investment. That's a guess of course, I don't have any idea of the costs involved in Jun-san's build. I'll have to talk to Jun-san some more about building a DIY amp like this. 

I imagine there will be high-end brands clamoring to build premium versions of amplifiers that include the Infineon GaN Class D boards, but even this relatively modest build is very impressive.

Ok, that's my first impression of hearing Jun-san's Infineon GaN Class D demo amplifier, and there will be lots more to come.

I'll be doing quite a bit more audio-visual listening with the Infineon GaN Class D demo amplifier for a while, including music videos on Blu-ray discs that I want to hear it play, and I'll update you on that as I go along.

Stay tuned, there's much more to come!

As always, thanks for stopping by, and may the tone be with you!

Previous articles in this series about the Infineon GaN Class D amplifier:

"World Premiere" of the Infineon GaN Class D amplifier technology! A new "SET" for the 21st Century? HERE

Exciting news: "... a landmark development in the century-long history of amplifiers." HERE