ISO: Tube headphone amp for Planar headphones

@freediver Thank you for the info regarding OTL designs. I was not aware of that being an issue. Because it's the internet I had to look it up myself and lo and behold you are correct. Please don't take it personally.  

My digital front end is Bluesound Node2 into a Border Patrol DAC then into an ARC SP-11 Mk2. To drive the HPA, I have leads coming from the tape out on my SP-11. This allows me to use my headphones for all sources including my California Audio Labs Aria CD. 

The problem I'm seeing with the APPJ PA1502A, Cayin HA-1A and the  Yamamoto HA-2 that @tooblue was recommending is that there are no US dealer/distributors. Not even AMZN and they carry everything. And not that I have anything against "Chi-Fi" but the Cayins I find are 100VAC for Japan.

I also looked into the Auris Euterpe but alas, as it's 4+ years old, there are only close out/used examples available from Serbia. So the search goes on but at the very least the OTL thing is a very valuable lesson. Thanks folks.

Happy listening.

 I've owned both the HA-1A & the CS-55A integrated amplifier..Both were SUPERBLY built & in 5 total years of ownership never a single problem or hiccup..
 Bloom Audio carries the HA-1A & offers LIFETIME support,including assistance with Warranty Support should a problem ever arise...
https://www.google.com/aclk?sa=l&ai=DChcSEwiP6vGJsOaJAxVpMdQBHaLlOx0YABASGgJvYQ&ae=2&co=1&ase=5&gclid=Cj0KCQiA6Ou5BhCrARIsAPoTxrC2L7ap_Z5p_STsrwAJ45J5tOLnZlikyc174vRAzXWhVacvjQe2Hw0aAoZJEALw_wcB&sig=AOD64_1jicn1DEJwizhLKkx4BwBh4desIw&ctype=5&q=&ved=2ahUKEwiHr-eJsOaJAxWR48kDHR2sIyoQ9aACKAB6BAgHEBk&adurl=

I'd recommend the Quicksilver Headphone amp, and it should fit nicely in your budget.... Excellent out of the box and even better with some judicious tube rolling.

https://quicksilveraudio.com/products/headphone-amplifier/

@freediver Thanks for the info on the Cayin. I finally found an image showing the internals and was impressed with how it looks.

https://cf.shopee.co.th/file/40719695d2fd237fd6c597227d88277f

And it is pretty outside as well. 

The other candidate is the Quicksilver HPA suggested by @larsman. What I like about it is it's simplicity and rugged build. And it's JUST a HPA; No extra electronics to drive speakers that I won't use. It's not as pretty as the Cayin but it gets rave reviews and it's built just down the road in Stockton CA. It is however almost $300 more... I've pinged Quicksilver to see if there's a dealer in the Seattle area. 

Decisions decisions...

Happy listening.