So on my first amp I have to have the input on tape and same for the second amp?
The tape outputs are always seeing whatever the input selector is set to so set the first amp's input to the desired device, CD, AUX, TUNER, PHONO, etc, set the second amp to tape input however that's accomplished, adjust the second amp's volume as needed.
The RCA's into the second amp could also utilize the AUX, TUNER, CD, etc, just not the PHONO, then set it's input to the one you chose to plug the RCA's into, again, adjust volume on the second amp "independently of the first" as needed.
My reason for suggesting the tape input on the second amp, this leaves the other inputs open for additional sources such as another tuner, cd player etc. Sure these could utilize the tape input also, but it just helps me to remember which is which if plugged into the correctly labeled input lol.
I use something similar with my video audio in my main rm. The TV optical output feeds into a DAC that's plugged into my tape input so anything feeding into the tv "DVD, cable box, computer, etc will play through the tape input when selected. So if wanting to hear anything video related I select TAPE A, then set my TV to the proper input, VIDEO 1, VIDEO 2, etc. When wanting to listen to music I disengage the TAPE A input and use the input selector on the amp to select whatever. My audio equipment is vintage, this allows me to route anything video related that doesn't have RCA outputs through the TV into the stereo.
Hope this helps rather than make things more confusing lol.