Electric Guitar Effects

Electric guitars are most often made with solid bodies since they depend upon electromagnetic pickups and amplifiers to produce the sound and are not dependent upon the resonance of the hollow body like the acoustic guitar.

The fact that the output is electrical has made possible a dizzying array of sounds produced by electrically and electronically modifying this electrical output. Besides the volume and tone controls on the guitar and on the amplifier, a variety of outboard devices are used to obtain custom sounds and effects. As an attempt to organize these effects, consider the following classifications:

Signal Reshaping

• Distortion and overdrive: In the early days of electronic music, vacuum tube amplifiers were used for processing the output electrical signals. Like any amplifier, these tube amplifiers had a maximum amplification above which they began to clip the peaks of the waveforms. While the resulting distortion may have disturbed the electrical engineers, a substantial fraction of the musicians liked the distorted sound and it became part of the musical medium.

  失真和过驱：在电子音乐的早期阶段，真空管放大器被用于处理输出的电信号。像任何放大器一样，这些真空管放大器都有一个最大放大倍数，超过这个倍数，它们开始对波形的峰值进行削波。虽然这种失真可能让电气工程师感到困扰，但相当多的音乐家喜欢这种失真的声音，它成为了音乐媒介的一部分。

  Now, in the days of solid state signal processing, outboard units are available to produce a facsimile of the old tube-type distortion. Some units actually incorporate a vacuum tube and do it the old way. Other electronics packages simulate the effect. The "tube-type" distortion is preferrable to many over the kind of distortion produced by solid-state amplifiers because the tubes just gradually rounded over the peaks as they went into distortion, whereas the solid state devices just chop off the tops of the peaks cleanly at the supply voltage point, producing a harsh distortion. One type of distortion device, employed as a distortion pedal, was called a "fuzz box".

  如今，在固态信号处理的时代，有外置单元可以产生一种仿真效果旧真空管类型的失真。一些单元实际上集成了真空管，采用旧方法实现这一效果。其他电子模块则模拟这种效果。与固态放大器产生的失真相比，这种“真空管式”的失真更受许多人的青睐，因为真空管在失真时只是逐渐削平波峰，而固态器件则在电源电压点干净地截断波峰顶部，产生一种刺耳的失真。一种用于失真效果器的失真装置被称为“fuzz box”。
• Compression: A "limiter" is envisioned as a circuit which prevents the output signal from exceeding a certain limit. If it did this by clipping, it would cause distortion, but if it can do it cleanly by just progressively reducing the amplification of the incoming signal, then it may properly be called a compressor. A compressor reduces the overall dynamic range by "compressing" the gain of high amplitude signals while maintaining the design gain for lower amplitude signals.

  Compressors are available as footpedal controls and can be used as an effect on electric guitar signals, for example. They can be used to obtain greater sustain for a string by setting the gain high and allowing the compressor to keep the output signal at a more-or-less constant level until the natural sustain of the string drops the signal below a certain threshold.

  压缩器可作为脚踏控制装置使用，并可用于电吉他信号的处理，例如。通过将增益调高并让压缩器保持输出信号在较为恒定的电平直到琴弦的自然泛音下降至某个阈值以下，可以实现更长的泛音持续时间。
  压缩：设想一个电路作为“限制器”，其作用是防止输出信号超过一定的限度。如果它通过截断来实现这一点，就会导致失真；但如果它能通过逐步减少输入信号的增益来实现这一点，那么它就可以被称为压缩器。压缩器通过‘压缩’高幅度信号的增益，从而降低整体动态范围，同时保持低幅度信号的设计增益。
• Ring modulation: In the context of signal reshaping, the ring modulator takes the signal from the instrument and adds a second signal from a local oscillator or signal source. The two signals are combined to produce the sum and difference frequencies, which are then the output of the device. This scheme was used in the electronic music of the 1950's. The output frequencies track the input signal frequencies, but do not equal them, so there is a shift from the original pitches. The ring modulator has been produced as a footpedal, and ring modulator type effects are included in some modern electronic effects boxes.
  环调制：在信号重塑的背景下，环调制器会从乐器中获取信号，并添加来自本地振荡器或信号源的第二个信号。这两个信号结合后会产生和频与差频，这些频率成为设备的输出。这种方案曾在20世纪50年代的电子音乐中使用。输出频率跟踪输入信号频率，但并不等于它们，因此会产生从原音高移位的效果。环调制器已被制成脚踏开关，而环调制器类型的音效也包含在一些现代电子音效箱中。

• Pitch Shifters: Microprocessor-based devices can take the signal from a guitar and shift its frequency base. This amounts to sampling the sound and reconstructing it at a different frequency, so a lot of computation is involved. These devices range from note-shifting foot-pedals to studio-based harmonizers.
  音调调节器：基于微处理器的设备可以将吉他信号采样并改变其频率基底。这相当于对声音进行采样并以不同的频率重新构建，因此涉及大量的计算。这些设备从音符转换的脚踏板到基于工作室的和声器都有多种类型。

Signal Augmentation

• Flanging: This effect involves mixing two copies of the same signal with one of them slightly phase shifted. Historically, it had its origin with studio engineers using reeel-to-reel tape recorders. They would make a copy of a tape and then feed the original and copy together to a recorder, having placed a pencil on the flange of one tape to slightly alter its speed. The slight speed change would not be enough to cause notable delay, but would be enough to cause the two waves to be "out of phase" with each other. The effect is described as a king of "swirling" sound, with notable pitch oscillations if it became more extreme.

  混响效果：该效果涉及将同一信号的两个副本混合，其中一个副本略微相位偏移。历史上，这种效果起源于录音室工程师使用磁带录音机时的做法。他们会复制一段磁带，然后将原带和复制带同时送入录音机，同时在其中一条磁带的法兰上放置铅笔以略微改变其速度。这种微小的速度变化不足以引起明显的延迟，但足以使两个波形彼此“相位偏移”。该效果被描述为一种“漩涡”般的音色，如果情况更加严重，还会产生明显的音调波动。
• Phasing: Similar to flanging, but without the frequency shifts. Produces a similar "swirling" sound.
  相位调制：类似于混响，但没有频率偏移。产生类似‘旋涡’的声音。
• Chorus: Splitting the two signals further apart so that they are over a cycle apart in phase allows you to perceive two distinct signals, like two voices together. Called "chorus", this effect is perceived as less pronounced than flanging and phasing. It is described as producing a "thickening" of the sound, like reverb.
  合唱：将两个信号进一步分开，使它们在相位上相差一个周期，这样你可以听到两个独立的信号，就像两个声音同时发出。这种效果称为“合唱”，其感知效果比混响和相位要弱。它被描述为产生一种“声音变厚”的效果，类似于混响。
• Reverb: Adding back in copies of the original signal with time delays so short they cannot be perceived separately.
  混响：将原信号的副本以极短的时间延迟重新加入，使得这些延迟无法被单独感知。
• Delay and Echo: Adding back in one or more copies with enough delay that they are distinguishable. This was sometimes done with tape loops, so that sounds would be heard repeated a number of times. Digital delay has made possible much more flexible delay and echo effects.
  延迟和回声：添加一个或多个可区分的副本，其延迟足够长。这有时通过磁带循环实现，使得声音会被重复多次。数字延迟使得延迟和回声效果变得更加灵活。

The Fuzz Box

A guitar effect which falls under the heading of distortion is the "fuzz box". This device uses a square wave generator in the form of a Schmitt trigger to introduce a variable frequency square wave to accompany or even replace the original signal. The proportion of clean to distorted signal can be adjusted as well as the combined gain.