Hi,
I allways recommend an LPF to avoid/reduce alias effects and reduce noise.
Regarding protection: I don't like the idea to short circuit the output of an Opamp.
* High current,
* maybe high temperature,
* maybe crosstalk the "short circuit" situation to the other channels via the power supplies....
* and worst of all: bringing the Opamp out of regulation .... overdiriving input and output stages, maybe even latch up
can be expected.
--> the use of a series resistor may prevent all this.
Some ADC have switched capacitors (sample and hold circuit) as input. This could cause ringing at the Opamp output. --> erroneous ADC reading may occur.
An RC to the ADC may help.
We see 8 + 8 (hopefully) identical circuits, but ADCs and DACs are missing..
The signal names are misleading: I assume
* signals ADCx are not connected to the ADC
* signals DACx are not connected to the DACs
Note: At the DAC circuit .... as soon as the jumper is pulled off the output will saturate at either supply rail. On audio signals this will cause a huge "plopp" maybe distroying the power amplifier or the speakers.
I'd rather calculate one fixed resistor for your desired "high gain" and use a [jumper in series with a resistor] in parallel to the fixed resistor to select low gain.
Even with the DAC circuit I recommend to use a RC LPF....to avoid ringing. In case of audio signals I recommend to use a true reconstruction filter.
Klaus
Added
In case the analog signals enter/leave the PCB you also should consider ESD protection and EMC filters.