Power
Foundation of good sound. The one change that improves every other box.
Foundation of good sound. Your washing machine, your dryer and your air conditioner all draw power in bursts, and that distorts the 50 Hz sine wave arriving at your system. Heavy industry filters the same distortion out under IEEE standards, because it overheats motors. In a stereo it shows up as a raised noise floor, softer bass, and an image that will not settle.
Do you need it? Yes, and first. This is the only pillar that improves every other box you own rather than just itself. A conditioner cleans what comes out of the wall and a linear supply replaces the plastic adapter feeding one particular box, so start at the wall and work inwards.
Before you spend, find out what else is on the circuit. A fridge, an air conditioner or a washing machine on the same ring is the usual source of the problem, and knowing that changes what to buy. Then count the plastic adapters behind your rack: each one is a switching supply sitting inside your system. We would replace the worst of those before buying anything else, and we would do the wall before the boxes.
In plain language: Linear power supply, Power conditioner
