Tube Rolling is the term given to plugging different manufacturers’ valves into your equipment and listening for a change in the sound quality.

Guitar amplifiers can benefit from tube-rolling, since their valves are deliberately overdriven so that they distort the sound. Different valves will distort differently when overdriven, so it’s a case of experimenting with different manufacturers’ valves and playing with the overdrive, until you get the sound you want.

For hi-fi, it’s probably more of an academic exercise, since hi-fi gear is designed to use valves in their linear area (ie without overdrive). In this region, one valve should sound identical to the next. If they don’t, then there’s a defect with either the valve, or the circuit.

Some audiophiles will claim to hear the difference between one valve and another of the same type costing ten times as much. These claims are hard to prove, since other factors (like Placebo effect and Confirmation Bias) can affect the results.

If you stick with the major mid-price valves, brands like JJ or Electro-harmonix for example, there is no need to spend silly money on “premium” valves with the hope of any improvement in sound quality… it’s largely illusory.