Our ears are still far more discerning than be best audio measurement equipment available today. People that rather believe their measurement equipment than their ears, better train their ears. I own one of the best audio measurement devices on the market, made by Audio Precision.
But it’s my ears that tell me when something is really good. The Audio Precision is fine for proving what’s wrong, never for how good equipment is. That doesn’t mean your hearing can't play tricks on you. When my brother was young, he didn’t want to eat Brussels sprouts. But when he was told French cauliflower was on the menu, he ate the sprouts with taste. The same phenomenon occurs when we listen to changes in audio. If we have low expectations of a given product, hearing a difference is already enough to experience that product as inferior. Keep that in mind when judging equipment.
Having said that, placing equipment on a vibration free shelf, rack or table can make a difference, especially equipment that holds the o so critical audio clock. Checking power chord polarity for minimal ground potential can give big sound improvements. We have discussed the importance of good cabling but that includes power cables too. If your equipment offers more interconnecting options. like AES/EBU and SPDIF, try both options to find the best result. If your d/a-converter uses an external switching power supply, try replacing it with a linear power supply. But whatever you do, don’t forget to enjoy music. For that’s what it’s all about.