It is a general consensus, that an Additional Pair of RCA Phono Connector Inputs are used, followed by quite a few metres of Copper Coil and Lead Outs, followed by RCA Connectors as Outputs and then an additional pair of Cables is to be used.
The same above stands for a Head Amp in use as well, but swap out the Copper Coil, for a circuit built with usually seen component types.
The suggestion is, and mostly presented as a subjective evaluation based on the idea, increased components in the signal path, deteriorates/adulterates the signal path, and the shortest signal path is working toward the ideal.
I have not seen any measured data, that clearly defines sound produced from a signal passing through a SUT or Head Amp' is an inferior Sound produced at the Speaker End.
Do keep in mind signal that is produced prior to passing through the Speakers Xover, is an electrical current. It is only when the electrical current/signal has travelled as far as the Speaker, is the time it becomes sound and is able to be evaluated by each individual. In most cases individuals do nit share identical attraction for the same produced sound. We are all unique and have sensitivities to how we are affected by sound.