Some information on Higher Fidelity HF-HA01
According to www.headphone.com.hk
(Chinese website), the HA01 is made by a "reputable" Japanese company, and has great synergy with Audio Technica cans.
Issue 298 of AudioTechnique Magazine (Hong Kong magazine) carries a review of HA01, using L3000 as the testing can. The writer said it is amongst the best solid state headphone he has heard so far.
The HA01 used a proprietary "Triacting Circuit" which essentially employs two voltage amplifier circuit to drive the same power amplifier circuit inside the headphone amp.
Looking a the published photos under a magnifying glass, the circuit layout and components application are both very neat and professional, and despite the similarity to the face plate, back plate layout as well as chassis compartment of HA-5000, the internal layout of HA01 is very different. (the location and execution of volume pot, and the heat sink and power supply arrangements are most obvious) Just by looking at the photos, I am convinced it is a different design.
In Hong Kong, the HA01 is priced (listed) at HK$4,225 (around US$540) whereas a HA-5000 will be priced (fixed) at ~ HK$7,500 (around US$ 960). Taking into retail discounts, I would say the HA01 is approximately half the price of a HA5000, and can be pretty good value.
The HA01 has only 1 pair of RCA input, 2x headphone out.
Hope this helps.