Analog Delay

Back in the Day

Before the days of more advanced audio technology, music employing a delayed echo had to be recorded in a naturally reverberant space. This was often an inconvenience for musicians and audio engineers. The popularity of an easy-to-implement real-time echo effect led to the production of systems offering all-in-one effects units. They could be adjusted to produce echoes of any interval or amplitude. The presence of multiple "taps" (playback heads) made it possible to have delays at varying rhythmic intervals. This allowed musicians an additional means of expression over natural periodic echoes. So, the technological change during the mid-1970s led to the birth of analog delay units. At that time, affordable delay chips became available.

Analog vs. Digital

An analog delay is an effective device similar to a digital delay because it is an all-electronic device that temporarily stores the audio signal to create a time delay. The analog delay differs in how it stores an audio signal. Both units sample the input signal by chopping the waveform into thousands of equally timed segments per second. The main difference between these two delays is that the analog delay unit converts each sample to an average voltage value.  

BBD

Instead of using ADC, numerical (digital) memory registers, the analog delay uses a sample and hold circuit to convert the continuous input signal to a string of voltage values, plus many capacitive storage devices known as bucket brigade devices (BBDs). The voltage stored in one bucket is poured into the bucket in sequence. The sampled voltage eventually reaches the output. The Strobe signal transforms the voltage from one registry to another. This is much like digital delay technology. The typical analog delay line has many of the same special effects. Unlike a digital delay, a narrower bandwidth limits an analog delay line. It is generally somewhat noisier. An analog delay's characteristic warm, smooth, and organic sound is due to its limitations, not because of any mystical mojo in a chip. Effects with BBDs at its core are a great example of how an effect can inspire a whole generation of musicians and artists. Nevertheless, it technically isn't a "perfect design."  

Musical Special Effects

The analog delay units became more popular by the end of the 1970s because they were less expensive to produce than digital delays. Back then, and even today, producers mostly used them as musical special effects. Many producers and musicians claim analog delay units have a warmer and fatter sound than digital ones. On the other hand, there are differences in processing. As time passed and the cost of digital components came down, digital delays have pushed the analog delay to a small corner of the market.