I have taken this text from an advert for a Ps Audio GCA 500 amplifier
Offered for sale: a PS Audio GCA 500. The amplifier is rated @ 525w/ ch 8 O., 1000w/ch 4 O, and features PS Audio's proprietary Gain Cell input stage.
If you are looking at the Bel Canto Reference mkI or mkII, you should definitely take a look at this amplifier. It is in excellent condition both cosmetically and physically.
If you are not already aware, this amplifier uses the same Bang and Olufsen ASP Circuit Modules as the Bel Canto, Jeff Rowland, PS Audio, Wyred4Sound etc... Without modification, these amplifiers would all be identical save cosmetics. The two badges that do make modifications to the signal path are PS Audio and Wyred4Sound.The PS Audio uses a proprietary Gain Cell and the Wyred4Sound rejiggers a couple key parts to raise the input impedence to 60.4kO.
A little less than a year ago I got a bug to hear this difference, so I purchased a PS Audio GCA500 and this D-Sonic amplifier (modified by Cullen to match the Wyred4Sound product) to have a listen and compare with my then reference Bel Canto Ref 1k. I ended up settling on my preference for the Cullen input stage, and bought a multi-channel Wyred4Sound amp. The PS Audio was a close second, which leaned to the warm side. I promptly sold my pair of Bel Canto Ref 1k mkI which, although nice to look at, were a step below the refinement of the amplifiers with modified input stages. Bel Canto now offers a mkII amplifier with an improved input stage. I've yet to hear it. I am sure it provides similar benefits to what you can own here at a +20% discount to a Wyred amplifier or pair of mkI amps. And a huge +55% discount to Bel Canto's mkII.