Interconnect Break In?

Does the preamp need to be on?

As @ozzy said there needs to be signal passing from the source to a load. Load is the Preamp in this case. Naturally the preamp would need to have the input selected for the CDP.

Could the preamp be set to the input the CDP is connected to and then be powered off? Depends on the preamp. Some preamps use relays or some other type of source switching device other than a mechanical input switch. do you know what you have?

As for break-in, burn-in, settle-in, what ever you want to call it, it’s not just the wire that burns-in. The RCA plugs need to burn-in.  The dielectric, insulating material that cover the bare wire needs to burn-in, settle-in as well. The signal energy actually travels in the space between the wires through the dielectric.

A load is needed to complete a circuit for current to travel in the circuit from the source through the load back to the source. No load, no current. No current no electromagnetic fields.

Does a closed circuit exist if the preamp is powered off? I think it depends on the design of the input circuit(s) of the preamp. What type of input switching is used to switch from one input to another? The basic type is a mechanical rotary contact switch. A more complex type of switching is done with relays. With relays what is the state of the contact when the preamp is turned off? Open, Closed?

Here is a schematic wiring diagram of an older Conrad Johnson PV10 preamp. It uses a manual rotary mechanical switch to switch from one source input to another. If the connected source is a CDP and the rotary switch is set to that source input there is a load connected to the CDP output jacks. (CDP connected to preamp using ICs.)

Balance Pot (R27), Volume Pot (R28). Those are in series with (R12) that connects the circuit back to the signal ground of the input jacks. (We have a closed circuit.)

There is also another circuit load depending on where the volume Pot control was set when the preamp was shut off, powered off.

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