I'm doing a project that the idea is to accept 3 audio inputs: 1 amplified input (27Vpp), a pre amplified input (6Vpp) and a microphone input (About 150mVpp).
Both amplified and pre amplified signals are balanced and came from a class D amplifier that has a 4 Ohms output impedance, for them I am thinking to use a passive attenuator, 'L' shaped to set the signal to about 2Vpp, bench testing apparently it worked fine (I don't really need studio quality). So, here is my first question: Is it the best option to attenuate the signal? Any other options? After attenuated, the signals go to the MUX (MC74HC4052ADWR2G). Do I need to be careful with the audio impedance matching with the mux input impedance?
I don't want to use a negative power supply, so I thought I'd give the signal a DC gain before going into the mux, because of the attenuator circuit i i thought i in using an AMPOP in the setup shown in the image: Is it a good solution? What consequences does it have for the audio?
The output of the MUX will go to an ADC, i was looking at the ADC datasheet and saw that its input impedance is high (about 22k) - compared with the 4 Ohms of the inputs. Do I need to do something to match the impedances? Or does the ADC "accept" a range of input impedances because it has a higher impedance input?