I have the Jaycar Headphone Amp w/ matching power supply. My unit was built for me as a gift from an Aussie DIYer who highly modified the unit inclusive of a JLH additional board for the power supply.
It is a superb unit, does who wish to follow over 6 months of tweaks and improvements to the Jaycar Headphone Amp send me a PM. I will provide a link to the forum w/ the mods/improvements.
I have since make some more mods to mine, which has basically become KHA I.5 now, it's been Franked in parts and become even more stunning, both in sound and in value. With the FrankenZero plus KHA I.5 together, it's got to be one of the greatest bang-for-buck combos out there! Not an expression I like that much, though really, value for money is something else. The FrankenZero goes way beyond such a concept and has become something else entirely!
I would love to know what mods you have made to your 'KHA', do you have that link there?
KHA I.5 has all the electrolytic caps replaced now with Nichicon Muse FA and Elna Silmic II versions, the greencaps near the inductors are now Russian PIOs of the same value and those nasty little ceramics have been vanquished and 47pF MKP WIMAs are in there instead. To say what was already a great little amp has been transformed, is almost understatement.
It's still burning in, both Frankie and KHA I.5 are at the 130 hour mark today.
My KHA II board is still waiting for Black Gates to arrive, mostly those fabulous .1uF NX series bypass caps that were brought to world attention by Matin Colloms a few years ago. And then there's the audio-gd power supply here, which I am in the middle of making the heatsink for now. I'll test it on KHA I.5, though it is destined for KHA II.
Look forward to seeing what you have done with your amp, mate!
P.S. OPA Moon is still the greatest gift one can give to this amp, IMHO!