Dirty power = Electrical noise (hash) = Distortion in the audio signal.
- Not hiss or hum.
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Symptoms of distortion from noisy AC power:
HF:
- High notes are ‘etched’ or ‘hard’.
- A vocalist’s voice sounds ‘grainy’ - and/or – has glare when belting out high notes.
- A violin sounds too strident. No tone or timbre. No delicacy.
- The high notes on a piano ‘ring’ unnaturally.
- Cymbals don’t shimmer, they crash.
- Unable to discern individual stringed sections in orchestral music.
- The instruments in a crescendo from an orchestra become confused - indistinct.
- Poor extension. Instead of feathering off into airiness, the notes might truncate.
+ much more
Midrange:
- An acoustic guitar - or piano - seems to have too much harmonics - more than the real thing. It might sound pleasing – but, not true.
- A horn or woodwind sounds too diffuse or bloomy – more than the real thing. In other words, the notes of the instruments have a fuzziness around the edges. There should be a solidity & transparency.
- Unable to determine if an acoustic guitar has nylon or steel strings.
- A vocalists voice sounds electronic – not natural.
+ much more
LF:
- Bass is a one-note thump.
- Bass is not tight – too diffuse or boomy.
- Unable to discern tone or timbre in the bass.
- Poor extension. Instead of feathering off, the notes might truncate.
- Difficult to follow the bass line. For both stringed instruments and drums.
- Unable to discern individual bass sections in orchestral music.
- Unable to discern bass riffs in orchestral music – while the full 96 piece ensemble is playing.
+ much more
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Black background:
- Lower noise floor.
- Ability to easily discern nuance.
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Some of the above symptoms may also be the result of poor room acoustics – or poor synergy between component/component – component/cabling.