Re: Signal attenuation when splitting an output
One general mechanism, and one more obscure.
General mechanism first: Outputs have output impedance, and inputs have input impedance. When plugged together you get a simple voltage divider formed by the two impedances. Modern audio interfaces use "bridging" terminations (not same as bridged power amp) where input impedance is 10x or higher than the output impedance for modest (1dB or less) insertion loss.
The obscure mechanism that coincidentally results in exactly 6dB loss, is when a balanced output with two hot signal legs (on XLR pins 2 and 3) interface with an input that shorts one of the two legs to ground, or ignores one leg. This is not very common.
Yes, but you should not need one...
JR