Such devices would most likely use what is referred to as "passive" power factor correction - typically using some kind of passive network with one or more inductors and capacitors.
The most effective means for power factor correction is active power factor correction, which requires an impedance matching network (e.g., using var caps or other mechanism for matching the impedance of the load.) This solution, however, is more expensive and complex, and there is a question as to how much of an audible difference this would make in audio applications, particularly for line level components. (By contrast, in designing amplifiers for powering plasma chambers for thin film deposition, active power factor correction is a matter of necessity - a couple kW of reflected power is not the healthiest thing for your amp).
The most effective means for power factor correction is active power factor correction, which requires an impedance matching network (e.g., using var caps or other mechanism for matching the impedance of the load.) This solution, however, is more expensive and complex, and there is a question as to how much of an audible difference this would make in audio applications, particularly for line level components. (By contrast, in designing amplifiers for powering plasma chambers for thin film deposition, active power factor correction is a matter of necessity - a couple kW of reflected power is not the healthiest thing for your amp).