Goldensound's post was aimed at folks (like me) who have no idea what any of the above means. After doing my due diligence a while back, I decided against using a speaker amp to drive my HE6. As your post illustrates, doing it safely and correctly requires more technical knowledge than I have. I imagine the same is true for many others.
Exactly the point that I was trying to make. I was just trying to encourage people to read up on class D amps driving headphones. I have tried a Class AB speaker amp on different headphones and got wildly different results dependent on impedance and voltage requirements. I have decided that I prefer to stay with the design parameters of the amps that I use with my headphones.
I would also question whether a $130 amp, designed for driving something completely different, is a good choice for $1500-$2000 headphones such as the Tungsten. I'm not saying go crazy, but amps from Topping, Holo, Ferrum, iFi, Schiit and others are out there that can drive these and are designed to drive them. I would say the same for the HE6.
Especially when there is the potential for damage to your hearing because of the way D class amps are designed and you will not hear it to know that it is being damaged. It's fine for someone on a forum to say I did it and it seems fine, I'd want proof that it is ok from the amp designer.
The author of the post I linked acknowledged that some D Class amps have different filtering such as those designed by Bruno Putzys. Fosi is using TI chips with swappable opamps. They are not designing the amplifier circuit, TI are, and there is not a mention of using these with headphones or any data on any impedance outside of 2,4 and 8 ohms on either the TI datasheet or the Fosi website, nor of the filtering.
I'm sure the Fosi is a fine D class amp for speakers for $130, but it isn't designed to drive headphones. I'm not anti class D, my previous 3 speaker amps were class D.
I also wouldn't trust a Hifiman adapter designed to work with the HE6SE which is 50 ohms and the Tungsten which is 135W and 155W depending on whether it is is single or double sided. Most here are not going to be swapping resistors in the adapter with any confidence they have the right value.
Again, to those that want to try this, you do you, but only if you know and understand the risks to both your headphones which are replaceable and your hearing which isn't.