Mike Atkinson wrote: ↑
Sat Jul 27, 2019 11:43 am
60 cycle hum
Electricity, especially when poorly grounded and poorly shielded will cause this noise.
Single coil electric guitar pickups will pick up this noise from electric sources (Double coil, or " humbucking" pickups cancel the noise).
It can be addressed, and reduced, with good equalization settings for the room, having sufficient amplification, so as to not open the board completely, and various gates and suppressors.
^^^^ What Mike said. If the term is strictly "noise" then yeah:
- 60 Hz hum from bad grounding or ground loops is the main culprit.
- white noise is broad spectrum (all audible frequencies) and perceived as "fuzz"
- pink noise if band limited (narrower frequency range) white noise
But wait, there's more! There are also unintended distortions that are considered and/or perceived as noise:
- amp noise: you ground the input (silent input signal) and the amp generates internal noise from noisy components
- Brownian noise: a distinct form of amp noise due to random electron motions in amp chips - does not happen with tubes AFAIK.
- phase distortion: some frequencies have a higher amplifier throughput speed than others so get out of phase with the original sonic content
- intermodulation distortion: the amp does not reproduce the original signal properly creating spikes and weird harmonics, perceived as noise.
- slew rate distortion: the amplifier cannot match the speed needed to amplify to the desired magnitude causing audible noise.
- clipping: the amplified signal exceeds to power rails and becomes a squared off wave generating nasty harmonics and badly distorting the signal. Some call this "headroom distortion".
- impedance distortion: a mismatch between the output impedance of the amp and the input impedance of the speaker causes waveform error.
- feedback: some of the output signal is routed back into the input causing a feedback loop.
- good 'ole harmonic distortion: the subharmonics are of greater magnitude than the primary frequency and/or harmonics are out of balance in general and/or incorrect harmonics are being generated.
I hope this is what you had in mind with the OP.