guenthi_r
Active Member
The pictures are the right. Maybe you should take a look into before posting.One of the pics in your links is the older 640-something, I think. The Solo and Duo look very similar.
Variations in RIAA conformity can boil down to tolerance specified for the caps/resistors used for EQ. When I modded my phono stage, I ordered parts at 1% tolerance, but the same components are available at 2%, 5%, and 10%, at lower costs.
So it isn't necessary for the circuit to vary, the tolerance on the components can vary and alter the performance enough to show in measurements.