Fosi Audio SK02 DAC Amp Headphone Amplifier Desktop USB C to AUX Digital to Analog Audio Converter Adapter Preamp Optical to 3.5mm 4.4mm Balanced Combo for Home Audio System

The device is built like a tank and weighs about 350 gm. The form factor and the hype is what made me try it.The volume knob can also be used to turn on/off just like how it works on the Fosi ZA3 Amplifier.The 3.5 mm headphone jack is flimsy and does not inspire confidence that it would last.I had the device fed with a high quality linear supply through the 5v input and used the WIIM Pro Plus as a source via the optical connection for the cleanest signal.I also tested it with AKG N60 NC in low gain, the Sennheiser HD25 II and Sennheiser HD650 in high gain. I have a lot more demanding and high resolution cans but this did not inspire me to try them all.The ESS DAC used may be state-of-the-art but the headphone amp sounds mediocre at best. It sounds thin (lacking body), low dynamics, narrow instrument separation, minimal vocal texture and tone, very cold and almost sterile sounding product.It's very likely that these are targeted for use as a stand alone budget DAC, competing with the likes of SMSL SU-1 but with more features and functionality thrown in, or as an all-in-ones for IEMs and other low impedance portable solutions for the digital nomads.It did not work for me as a dedicated desktop solution although this is exactly the form factor and functionality I was looking for.In my books this sounds like good quality Radio Fidelity! YMMV...