The Rowland PC1 is listed at $1500. It can be applied to the Rowland 201, 501, Concerto, Capri, Continuum 250. It does not apply to any of the 300 series amps nor to the Continuum 500 because they already contain equivalent circuitry. PC1 transforms a 110V AC signal into a steady 380V DC current, regardless of voltage spikes/fluctuations/etc. . . The idea is to avoid distortion caused by the fluctuating rate of recharge of capacitors in the affected component when fed an AC voltage. PC1 should not be applied to 3rd party amps/pres unless you have checked with JRDG. It has been suggested that PC1 may require significant break-in in the range of several hundred hours. I am evaluating one in my system and will post findings when I have sufficient data points. I know that Rowland has already brochures but the jeffrowland.com web site has unfortunately not yet been updated with the new info.