The BHSE is tube output- Doesn't sound distorted to me.I have an Ayon Skylla 2 DAC- Tube output- extraordinarily clean and detailed sound- no roll off at all to my ears. I compared it to several top solid state designs and to my ears noticed no more distortion- just better musicality.One of my comparisons was between my Ayon and the renouned Reimyo DAP999EX- fully solid state, and known to have superb purity of sound. I compared both DAC's in my home for several months. The Ayon was no less pure, transparent, or clear- just a bit more natural. Better suited to headphone listening where those drivers are right on my ears. The Reimyo presented the detail in a more piercing manner, while the Ayon in a more organic manner. However, the amount of information I heard on both DAC's was equal.I don't believe we need to use the best headphones in the world with the worst electronics. I believe the SR-009 needs a DAC that does not have piercing detail but rather something a bit more laid back, smooth, natural, etc.... No distortion needed. Maybe there are Solid State Dac's that can do the job as well. I don't doubt that. I once tried the QB9- a solid state USB DAC and it was not harsh on my ears at all. It was to my ears more easygoing, a bit more laid back, and even slightly warm. However, it did not touch the transparency, musicality and PRAT of the Ayon or the Reimyo.There are many avenues to reach a certain point. We all need to use what works. I do not believe however that tube output is fundamentally flawed.