This is a refined version of the popular class A MOSFET amplifier, with reference to F5 improved version. In this new design, the symmetry of the upper and lower half of the circuit is optimized by adding in a variable resistor to compensate for the N-ch and P-ch JFET discrepancy. The adjustment usually has to be carried out with equipment, such as oscilloscope or distortion analyzer. Otherwise one can adjust to their taste. If one do not bother to take this adjustment into their consideration, the original design is already very good. We still supply the original design PCB.The original design listing title is "Mosfet pure class A amplifier thick copper PCB !" The PCB has a board thickness of 2mm, and copper thickness of 70um !! This is four times normal board copper thickness, and two times copper thickness compare to our previous version. PCB dimension : 105mm x 62mm This is a single channel amplifier PCB. Two PCBs are needed to form a stereo amplifier. We provide schematic and part list to buyers by EMAIL( to be attached to the shipment notice). We also have the power filtering board with reference to First Watt amplifier series that is a perfect match with this amplifier board. Please check our other auctions. We do air shipping worldwide at US$6.00. We welcome combine shipping. On Mar-05-09 at 01:26:53 PST, seller added the following information: SquareTrade squaretrade warranty v2.0 Powered by SoldEazy