What do you think of this preamp design?

Kirkus, I completely agree with you regarding the price of this unit. I'm not an electronics expert so I can't attest to the soundness of the design, but there is no US or EU based company (even if they manufacture in China) that can make a preamp or amp of this build quality for the price they're asking for. If this was a US based company, I wouldn't be surprised if the preamp was priced at $6000+.

Ralph, I appreciate the offer. I may offend the designer of my single ended amp if I ask him to change his amp in any way (He is pretty legendary and has been building audio equipment since the early 70's). But I'll ask.

What we're talking about is a textbook integrator circuit . . . the 1 Meg resistor and 100nF cap are even common values, giving a 0.1 second time constant, equivalent to 1.6Hz. The reason behind the extra RC on the input is unclear, as it doesn't create a second-order slope . . . but this is definitely more of a conceptual schematic than an accurate circuit reference. I'm giving him the benefit of the doubt.

I think that the Chinese high-end audio industry may be in the same state today as the Japanese industry was in the late 1960s . . . that is, with some interesting designs with their own unique cultural flavor are starting to be available for export. And amidst a sea of cheap manufactured goods and copies of Western legacy gear, I think this is the sort of thing that consumers of high-end audio should take notice of.