I know that the proper connection for a cd player on a vintage amp is the Aux input. Compared with the new gear, that has the dedicated cd input, is there any loss in sound quality?
The 'aux" input, or any other line level input, might be input level restiricted to about 1-1.5 volts. With the 2-3 volt output level from a CD/DVD player, you might overload the "aux in" on the older amp on loud passages. Try the "tape in" as it generally has less circuitry involved and will often times offer better sound quality over "aux in".