Getting good results is about impedance matching the signal going into the PA, most PA’s will be able to handle the different levels from different sources, it’s a question of using the right inputs and setting them correctly!
As an example if you look at the inputs on this Yamaha Stagepass link you can see sockets 1 to 4 have switches for instrument and line level input, plus a phantom power source required by some mic’s. Sockets 1 - 4 are can accept XLR cables, the CABLES can be either balanced or unbalanced, for long cable runs balanced cables will prevent signal interference and audio errors, Sockets 3 -4 also have a centre socket for a 6 mm jack plug (standard guitar jack).
https://uk.yamaha.com/en/products/proau ... oduct-tabsYou will also see a number of other different types of input/output connectors, these are for things like audio output from player and iPad type devices or output to monitor speakers/headphones.
Below is a link that explains Instrument level input, if you want know about other inputs click the appropriate link on the page:
https://www.sweetwater.com/insync/instrument-level/The manual on the Tech 21 Liverpool states that the output has unity gain, in other words the signal going in will match the signal going out:
https://www.sweetwater.com/insync/what- ... ld-i-care/The above information holds good for audio interfaces and direct connection to a computer, if you are making a connection to a computers sound card this will normally be “Line In” (a standard output socket for headphones will match this). The other connection you may have on a sound card or device is SPDIF, this is a fibre optic connection for high quality results, in this case the device providing the signal is doing the conversion from audio to digital signal (ADC) and by passes the sound cards input conversion. When the computer has done the processing for you to be able to hear audio it has to convert the digital signal back to analogue (DAC).
Note: Often sound bars for TV will have an SPDIF connection, it’s worth considering because a fibre optic lead can transfer data faster and should give the best results, it’s also very thin and neat.
Regards
Gary