Delay (audio Effect) - Digital Delay

Digital Delay

The availability of inexpensive digital signal processing electronics in the late 1970s and 1980s led to the development of the first digital delay effects. Initially, they were only available in expensive rack mounted units but eventually as costs came down and the electronics grew smaller, they became available in the form of foot pedals. The first digital delay offered in a pedal was the Boss DD-2 in 1984. Rack mounted delay units evolved into digital reverb units and on to digital multieffects units capable of more sophisticated effects than pure delay, such as reverb and Audio timescale-pitch modification effects.

The earliest known design, possibly the first, was prototyped at a Boston based Sound reinforcement company in 1976. The core technology used a Reticon SAD1024 IC. This chip and design found it's way into the well known Rockman amplifier some years later. In the 1980's this design was used by BOSS for their mass production product.

Digital delay systems function by sampling the input signal through an analog-to-digital converter, after which the signal is passed through a series of digital signal processors that record it into a storage buffer, and then play back the stored audio based on parameters set by the user. The delayed ("wet") output may be mixed with the unmodified ("dry") signal after, or before, it is sent to a digital-to-analog converter for output.

Many modern digital delays present an extensive array of options, including a control over the time before playback of the delayed signal. Most also allow the user to select the overall level of the processed signal in relation to the unmodified one, or the level at which the delayed signal is fed back into the buffer, to be repeated again. Some systems today allow more exotic controls, such as the ability to add an audio filter, or to play back the buffer's contents in reverse.

As digital memory became cheaper in the 80s, units like Lexicon PCM84, Roland SDE-3000, TC Electronic 2290 offered above 3 seconds delay time, enough to create background loops, rhythms and phrases. The 2290 was upgradable to 32 seconds and Electro-Harmonix offered a 16-second delay and looping machine.