Comb filter. In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced spikes, giving the appearance of a comb. Applications[edit] Comb filters are used in a variety of signal processing applications. These include: In acoustics, comb filtering can arise in some unwanted ways. Technical discussion[edit] Comb filters exist in two different forms, feedforward and feedback; the names refer to the direction in which signals are delayed before they are added to the input.
Comb filters may be implemented in discrete time or continuous time; this article will focus on discrete-time implementations; the properties of the continuous-time comb filter are very similar. Feedforward form[edit] Feedforward comb filter structure The general structure of a feedforward comb filter is shown on the right. Where is the delay length (measured in samples), and. . . , giving . . MXR Phase 90. History[edit] The Phase 90 was released in 1974. It was the first pedal sold by MXR and helped launch the company.[1] The original came in a simple orange enclosure with MXR's "script" logo. In 1977 MXR changed its logo to the current "block" logo. There was a transitional period in which some Phase 90’s with script logos had box logo circuits, and vice versa. Production ceased when MXR went bankrupt in 1984.[2] When Jim Dunlop bought the MXR brand, production resumed.
Paul Gilbert has described the Phase 90 as Van Halen I tone in a box. Description[edit] The Phase 90 has an orange enclosure. Speed - Controls the speed of the phasing effect. References[edit] This page uses content from GearWiki at M-101_Phase_90. Phaser (effect) A phaser is an electronic sound processor used to filter a signal by creating a series of peaks and troughs in the frequency spectrum.
The position of the peaks and troughs is typically modulated so that they vary over time, creating a sweeping effect. For this purpose, phasers usually include a low-frequency oscillator. Spectrogram of an 8-stage phaser modulated by a sine LFO applied to white noise. The electronic phasing effect is created by splitting an audio signal into two paths. One path treats the signal with an all-pass filter, which preserves the amplitude of the original signal and alters the phase.
The amount of change in phase depends on the frequency. When signals from the two paths are mixed, the frequencies that are out of phase will cancel each other out, creating the phaser's characteristic notches. The number of all-pass filters (usually called stages) varies with different models, some analog phasers offer 4, 6, 8 or 12 stages.
Effects Explained: Modulation—Phasing, Flanging, and Chorus. Adapted from the book Guitar Effects Pedals: The Practical Handbook (Backbeat Books) In Part 4 of Gibson’s Effects Explained series we’re going to look at modulation effects. This group includes phasing, flanging, chorus, vibrato and tremolo, rotary speaker effects, and octave dividers, the latter of which I have loosely grouped in here because … well, they don’t fit in overdrive or delay, do they? Later analog versions of the first three of these—phasing, flanging, and chorus—do, as a matter of fact, use much of the same technology as echo and delay units, although with chips having shorter delay times, but it makes sense to include them here because their obvious sonic characteristics are of a type with other units made from very different kinds of circuits.
Most such effects were developed in an effort to add depth, dimension and movement to the guitar’s natural sound without necessarily distorting it, strictly speaking. Want more Effects Explained? Phaser (effect) Timeline of recordings with a flanging effect. Flanging is a time-based effects unit that occurs when two identical signals are mixed together, but with one signal time-delayed by a small and gradually changing amount, usually smaller than 20 ms (milliseconds). This produces a swept 'comb filter' effect: peaks and notches are produced in the resultant frequency spectrum, related to each other in a linear harmonic series. Varying the time delay causes these to sweep up and down the frequency spectrum. Part of the output signal is usually fed back to the input (a 're-circulating delay line'), producing a resonance effect which further enhances the intensity of the peaks and troughs. The phase of the fed-back signal is sometimes inverted, producing another variation on the flanging sound.
A flanger is a device dedicated to creating this sound effect. Examples of music recordings with a flanging effect include: 1940s[edit] "Mamie's Boogie" (1945) by Les Paul. 1950s[edit] 1960s[edit] 1970s[edit] 1980s[edit] Understanding Audio Effects - An Overview of Types and Uses for Performance + Production. An Overview of Audio Effects This week we’re taking a step back to the basics in order to give our beginner students and readers an overview on audio effects and how they work. If you’re just starting out on your audio production journey, you’ve most likely come across effects in your gear or software.
These might be delay, reverb, distortion, compression, phase, flange, pitch-shift, ring modulators or filters. This article aims to get you familiar with these terms and what these devices do. In future installments of this series we will get a bit deeper on specific types of effects (as some subjects such as reverb require an article of their own.) What are Audio Effects? Audio effects are devices (analog or digital) that are used to intentionally alter how a musical instrument or other audio source sounds. A Brief History of Audio Effects Modern day effects are all a result of the evolution of technology and the advent of recorded sound. Add. Hardware and Software Effects Dynamics Distortion. All-pass filter. They are generally used to compensate for other undesired phase shifts that arise in the system, or for mixing with an unshifted version of the original to implement a notch comb filter.
They may also be used to convert a mixed phase filter into a minimum phase filter with an equivalent magnitude response or an unstable filter into a stable filter with an equivalent magnitude response. Active analog implementation[edit] Figure 1: Schematic of an op amp all-pass filter This implementation uses a high-pass filter at the non-inverting input to generate the phase shift and negative feedback to compensate for the filter's attenuation. In fact, the phase shift of the all-pass filter is double the phase shift of the high-pass filter at its non-inverting input. Interpretation as a Padé approximation to a pure delay[edit] The Laplace transform of a pure delay is given by where is the delay (in seconds) and is complex frequency. We recover from above. Implementation using low-pass filter[edit] is , where for. Band-stop filter. Narrow notch filters (optical) are used in Raman spectroscopy, live sound reproduction (public address systems, or PA systems) and in instrument amplifiers (especially amplifiers or preamplifiers for acoustic instruments such as acoustic guitar, mandolin, bass instrument amplifier, etc.) to reduce or prevent audio feedback, while having little noticeable effect on the rest of the frequency spectrum (electronic or software filters).
Other names include 'band limit filter', 'T-notch filter', 'band-elimination filter', and 'band-reject filter'. Generic electrical schematic of a simple band-stop filter Examples[edit] In the audio domain[edit] Anti-hum filter For countries using 60 Hz power lines: Low Freq: 59 HzMiddle Freq 60 HzHigh Freq: 61 Hz This means that the filter passes all frequencies, except for the range of 59–61 Hz. For countries where power transmission is at 50Hz, the filter would have a 49–51 Hz range. Anti-presence filter Low Freq: 1 kHzHigh Freq: 4 kHz Wave trap See also[edit] History and Development of the Phaser Effect - Music Technology Student. Description of the Phaser Effect: A phaser is an electronic sound processor used to filter a signal by creating a series of peaks in the frequency spectrum; each peak is modulated so they vary over time, creating a resonant sweeping effect.
Phasers usually include a low-frequency oscillator. The phaser combines the original signal with a copy of the same signal which is slightly delayed and out of phase with the original, this means the two signals reach both the highest and lowest points at different times. The effect works through a line of filters, passing all frequencies equally, however shifting their phase relationship (In Phase, Out of Phase, Phase cancellation).
When these frequencies have been shifted, some cancel out whilst others add notches and peaks in the response – making the sweeping sound when a modulation is added. A phaser is commonly used as a guitar effect. Controls of the Phaser Effect: LP/HP Knobs –Controls the cutoff frequency of the lowpass and highpass filters. Q. What's the difference between phasing and flanging? I have several phasing and flanging plug-ins, and the same effects on my Korg Triton. While not identical, the two effects seem quite similar. What's the difference between the two? Neil Morley SOS contributor Steve Howell replies: These two types of effect are indeed related in many respects, and they are both created by delaying the signal by small amounts and then mixing this with the dry signal.
If you delay a simple sine wave and superimpose it on the original waveform, when the phase of the two sine waves is close, the sound is reinforced in some places. But when the two are exactly 180 degrees out of phase and exactly equal in amplitude, this results in total cancellation. It's simple maths — add +5 to -5 and you're left with nothing. With more complex waveforms, superimposing the same signal and delaying it slightly creates what is known as a 'comb' filter — the frequency response of the filter has various peaks and troughs of amplitude ('teeth') across the harmonic spectrum. Phaser (effect) Comb filter. Flanging.
Origin[edit] As an audio effect, a listener hears a "drainpipe" or "swoosh" or "jet plane" sweeping effect as shifting sum-and-difference harmonics are created analogous to use of a variable notch filter. The term "flanging" comes from one of the early methods of producing the effect. The finished music track is recorded simultaneously to two matching tape machines, then replayed with both decks in sync.
The playback-head output from the two recorders is mixed to a third recorder. Despite subsequent claims over who originated flanging, Les Paul discovered the effect in the late 1940s and 1950s, however, he did most of his early phasing experiments with acetate disks on variable-speed record players. Others have attributed it to George Chkiantz, an engineer at Olympic Studios in Barnes, London. Kendrick's setup to control flanging A similar "jet plane-like" effect occurs naturally in long distance shortwave radio music broadcasts. Artificial flanging[edit] "Barber pole" flanging[edit] Phasing & Flanging - what's the difference?