This is a DIY headphone amp using the 6C45Pi tubes, similar to the Papa Rusa or Bottlehead Mainline amps.
It has a switch for HiZ and LoZ (12:1 and 8:1 ratios)
In terms of performance, it has alot of power (500+ mW on LoZ, and over 200mW on HiZ)
The frequency response is within 1dB between 20Hz and 20kHz, with a slight high frequency tilt.
Confirmed that there is no oscillation.

The only issue is a very low-level hum that is only present when there is no signal playing. I confirmed with measurements (attached in the pics) that the hum disappears even with low level music.
Due to above, the amp would work best with either dark sounding or power hungry headphones.
Lastly, the paint job is not the best and has some imperfections.

I am building a few of these, and this was my prototype in order to iron out details for the next build.
This amp is using high quality parts throughout --
* Hammond 269GX power transformer and 155H choke
* Hammond 119DA output transformers
* Hammond chassis
* Nichicon LKX power supply caps
* NKK gold-plated switch
* PEC KKA volume potentiometer
* Custom cascode CCS PCB's
* Includes a matched pair of 6C45Pi tubes (matched on my uTracer)
This amp would be fairly easy to tweak, whether it is to try LED bias (or add a cathode bypass cap), new coupling caps, or even rewiring
the tube sockets for a 5842 or D3A.

Attached is a pic of prices (albeit some can be found cheaper elsewhere). Once you add the PEC (~$38), tubes, and all the other parts the BOM is well over $400.
I am asking $350 + $20 flat-rate shipping within the US.