I recently acquired a NOS 502a in a store in raon. It is the last piece daw and on sale for 2.9K but since they don't have the box na and looks a bit dirty, I huggle for the price and the owner gave it at 1.8K ! When I tested it at the shop, compared to other chinese amps they have, it stood out, sounding more like a japanese amp, a classic marantz if I may. The sound was warm, full bodied but has clarity and detail, considering the fact that a cheap chinese speakers were used also.
Now what puzzled me was the brand of this 502a is not Konzert but BSE7VEN (you decipher it)
. I checked the innards and looks the same as the konzert posted here, in fact, this BSE7VEn uses 8 pcs. of Toshiba output transistors. Now I'm assuming this 502a amp is not exclusive for Konzert but, in fact, an OEM product that can be labeled to any brand which acquires it. The fascia , back and innards of the amp is a replica of the Konzert 502a, though the emblem and stamp name on the top cover is BSE7VEN.
But I'm not compalining but merely stating the fact that Konzert products are also off the shelf modelsand not exclusive design for them.