STAX headphone amplifier "Pluto 801A/SE" p2

Let me show few more examples, how to put this system on even higher sound quality level. 

Warning, additional expenses ahead.

I´ve seen a 801/VT62 on ebay sale. I was curious what changes
are needed to currently used setup.
About 220€ on ebay for a pair, sure it is worth to take a time and recalculate whole amplifier. Currently used heater supplies are not strong enough, update is neccessary..
In A1 class, is possible to get 155Vrms STAX output, enough for medium volume listening + some music peaks.   (LL1660 transformers wired as 4:4,5)  For serious loud listening class A2 modification is needed. As you can see, some complications here and there; but this thing is doable !  
At same volume (100dB) is possible to have with 801 3-4,5x less distortion; than with 2A3 today. Which is really small, for feedback-less amplifier!   (2A3  15Hz....50kHz (-3dB) ~2% THD)
At this level, I recommend to think about amorph version of output trasformers. (~250€/pc) More music details, and less transformer losses, is where amorph core excels.
One remark, this version has less volume headroom than 2A3 version. But will sound better for jazz and similar smooth music genres.

Update 17.5.2016 - Working on directly heated triode input driver, to replace the modern 12AX7WB. Historical tubes sounds nicer than noval types, but are not very hum forgiving. It took about week of work to remove hum, it is fixed now. Sounds way richer in bass extension, treble is softer but does not lack details! Lovely music with detailed soundstage, best tweak so far.  (MAZDA HL23DD)

2A3 JJ 40W,  High Current variant - i have been looking at LL1677 transformer datasheet, recalculated it with this big tube made in Slovakia. Distortion profile looks very good compared to 801A  and clean, mostly only a little 2nd harmonic. So you can get cleaner sound than 801A, and with more power.
Another benefit is much bigger headroom, theorethical max output 282Vrms (!). Step up ratio of transformer is responsible for this (1:2)
(801A example is 1:1,125) Triodes have smaller distortion in area of higher current and higher impedance. This example is about that.  .
If you do not care about consumption (similar like 300B speaker amplifier), consider this version.