Oatley released a headphone amp kit based on the OPA2134 - K465. A CMoy style simple HP amp based on the OPA2134. Oatley guarantees genuine OPA2134s and I have validated that. I received an early release which was assembled with pot and sockets on board. These were removed and the good input caps replaced with Russian PIO caps.
A larger ABS enclosure was used than the last two HP amps to accommodate the cct. brd and two 9V lithium batteries. The batteries are converted to differential supply on board - +/- 9V. The enclosure is lined with Al foil top and bottom and is earthed.
Once more my "safe on" wiring using the changeover switch on the input socket ensures the amp cannot accidentally be left on and drain batteries. The sound is good with excellent clarity, good volume and drive. The kit should be simple to assemble. The kit is complete with 9V battery clips and the ability to also use AA battery holders. You can see I am now spoiled for choice with three HP amps, one with the PT2308 chip and the others with OPA2134 chip.