Re: Please help me understand Chorus,Flange, Delay and phase
Alright, let me break it down...
A tape delay uses a loop of tape to delay the signal by some amount. An analog delay uses a Bucket Brigade Device (BBD) that makes a crude recording of a piece of the signal into an array of capacitors, also delaying the signal by some amount. The degradation of the audio signal is a little different between the two, but the signal will degrade (usually rolling off higher frequencies) the more times it is regenerated through the loop. A tape loop set for infinite repeat will halt further degradation, whereas a BBD will not, at least not as much. A true digital delay uses an analog-to-digital converter to sample the input signal, then delays and re-mixes the signal in a DSP chip before using a digital-to-analog converter to produce the output signal. You will tend to hear less degradation in a digital delay because the signal does not need to be resampled with every regeneration - it is only sampled once. Any degradation is caused by mathematical roundoff errors or intentional analog modeling algorithms.
Flanging takes the input signal, delays it by some amount through an echo circuit, then mixes this back with the original signal. This causes certain frequencies (and even harmonics) to be filtered out, while others are enhanced. Phase shifting does a similar thing, but uses a simple resonant circuit that will delay some frequencies more than others. In a phase-shift circuit, the different frequency components of the signal are delayed by different amounts of time; in a flanger all frequency components are delayed by the same amount of time.
To get the "swooshing" sound of a flanger or phase shifter, the delay time is modulated up and down slightly. This causes the affected frequency notches and resonant peaks to shift as well, introducing the swirling effect.
A chorus usually uses a tremolo/detuning circuit and a time delay to take one signal and make it sound like two. The main difference between chorus and flanging (as I understand it) is in how much detuning is involved.
A Leslie relies on the different dispersion of different frequencies out of a speaker. As the speakers in a Leslie cabinet rotate, higher frequencies roll off faster when the speaker is not pointed toward the listener, while low frequencies have less directionality. This is a different kind of swirling effect that is not easily modeled in the digital domain.
This is a simplified explanation, but the take-away is that these are all similar effects that result in subtly different frequency content of the output audio. You can often get away with using one in place of the other, but it will not sound exactly the same if you do.
