So Patrick, you say to bias at 2.88 watt, watt is the point. The amp is less than 25% efficient. Wasn't it designed to be 10 watt into the load. You are looking at +40 watt dissipation (per channel), will that not make them run a little hot. You obviously not built or tested one. Here is mine you can see that it was getting very hot to run at specified power. Power supply is external.
![20190420_200604[1].jpg](https://www.diyaudio.com/community/attachments/20190420_200604-1-jpg.1352100/ "20190420_200604[1].jpg")
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Here is an early (about 20 years ago prototype. Big heat pipe with fan at the bottom. Before you tell me the fan is blocked, no it does not stand on the fan it is just on the table for the photo. Imagine if it stood on the fan and powering it up. It would spin around and roll up all the wires. 😟
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No pun intended but the JLH sounds like honey amongst lemons. It sounds so good that I use it exclusively on HD800 headphones. I wonder what (watt) JLH would write in these comments if he was around. Probably roll around the floor laughing. Think of it, JLH simulated his amp using a log book or maybe a slide rule.
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Imagine that you designed a product in 1969 and in 2024 still people are arguing how to make a perfect design better. I don't think any of you can claim anything even close with or without simulators. Those days when the design is perfect, you leave it alone. JLH second "improved" design, one I also have do not even come close to his original. I believe he may even have had an XT desktop computer second time round.
Sorry, I am very confused these days, my bad. I also built the Hiraga, but never took a picture of it. I tried to demonstrate the massive heatsinks required for class A operation I guess. And yes HD800 runs from JLH. The top one. I could reduce the standing current but never bothered, once it is good don't mess with it.