What do you think of this preamp design?

It looks overly complex... A very competent solid state line stage could easily be built with about 1/3 the components. The op-amp in the feedback loop looks to me like an outright design problem...

The opamp is obviously an integrator (DC servo) used to set the quiescent conditions of the "BPM-7110" module, which appears to use current feedback, and a very high output impedance (current drive). The buffer stages are used to interface with non-CAST components. Really not so complicated.

Atmasphere, there's certainly not enough information here to trash this design so thoroughly, and English is obviously not his native tongue. While this is also not the way I go about designing a linestage, it's about as thoroughly "Power Paradigm" as it gets. To me, his stuff looks interesting, unconventional, and definitely reasonably priced compared to many.

Kirkus, if that's a servo, as long as it is handled properly I would expect it to work fine. The schematic really did not offer timing data, and there should be some integration at the output of the opamp else the servo will not work correctly. We use servos in our preamps too as our outputs are direct-coupled. I agree his English could be better...

Dracule1, I was not proposing that the amp be modified by anyone in particular, and it is certainly work that the manufacturer could easily do. If you *did* decide that this is something you were interested, I would be happy to talk to whomever made your amp so they would know how to do the mod.

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.