A lot of good comments have been offered above, most of which I agree with. However, I would add that references I have seen in the past to the ability of a system to be "revealing" have often confused the ability of the system to reveal musical detail and information with its ability to reveal differences between components, cables, tweaks, etc. They are two different things.
While a reasonable level of quality must be present for a system to be revealing of differences between hardware, there are many ways in which an increase in the ability of a system to reveal hardware differences can have nothing to do with the ability of the system to reveal musical information. And in fact an inverse relationship may often exist, such that increased ability to reveal hardware differences may in some cases reflect deficient design and the likelihood of reduced sonic quality.
Some examples follow. In each case it is assumed that everything else is equal:
1)A component having high output impedance will be more revealing of cable differences than a component having low output impedance.
2)A speaker having low impedance will be more revealing of cable and amplifier differences than one having high impedance.
3)A speaker whose impedance varies widely as a function of frequency will be more revealing of amplifier differences than one whose impedance is relatively constant.
4)Electronic components whose design is more susceptible to ground loop issues will be more revealing of interconnect cable differences than those that aren't as susceptible.
5)Unbalanced interfaces will tend to be more revealing of cable differences than balanced interfaces.
6)A component having greater susceptibility to emi/rfi problems will be more revealing of differences in cables, power cords, placement, and other factors than a component that is less susceptible.
7)Likewise for a component that generates more emi/rfi than another component.
8)A component having greater sensitivity to AC line voltage variations will be more revealing of power cord differences than one that is less sensitive.
9)A reason that is often cited for sonic differences between power cords is the constraint that the inductance or other characteristics of the cord may impose on abrupt changes in AC current demand, that may in turn occur as a result of the dynamics of the music. Class A power amplifiers will be much less revealing of those differences in power cord behavior than Class AB or Class D power amplifiers would be, because their AC current draw varies much less as a function of the amount of power that is sent to the speakers.
10)A moving coil phono stage that can't handle ultrasonic frequency components gracefully, without intermodulation effects resulting at audible frequencies, will be more revealing of differences in the capacitance of the phono cable than a phono stage that has no problems handling ultrasonic frequencies.
11)Sonic differences between digital cables depend greatly on the happenstance of a complex and largely unpredictable set of relationships and interactions between the parameters of the cable, including length, impedance accuracy, shielding effectiveness, shield resistance, propagation velocity, etc., and the technical characteristics of what the cable is connecting, including signal risetimes and falltimes, impedance accuracy, jitter rejection capability, ground loop susceptibility, etc.
Many other comparable examples could be cited.
Regards,
-- Al