Sound Principle:
Digital v Tape Delay

By Jay Frigoletto

While the concept of delay may seem basic at first glance, there’s more to this deceptively simple concept than meets the eye. A collection of popular effects including flanging, chorusing, phasing, and doubling all belong to the family of time-based effects, only the most basic of which is delay. At its simplest, delay takes an audio event and postpones it for a time. This can be for creative purposes in a mix, or for purely utilitarian purposes, such as time-aligning different speaker clusters in a PA system, or even the individual drivers within a single speaker cabinet.

Before the advent of digital signal processing, studios would often use an extra tape recorder and splice a piece of tape together to create an endless loop. A signal would be fed to the record head, and then read off the reproduce (repro) head, which, being physically separated from the record head, would play the signal back delayed in time. Using different tape speeds could change your delay time. For longer times, two tape machines could be set up next to each other with the tape coming off the supply reel of the first machine, passing its record head, then run over to the second machine where the repro head would play it back delayed in time, and finally stacked on the take-up reel of the second machine. The length of delay would depend on the distance between the machines. In some cases, people even set up rollers on top of mic stands to artificially extend the tape path between the record and repro heads on a single machine, allowing for very long tape delay loops.

Tape was not the only way to delay signals in the early studio. In the 1970s, integrated circuits became available that would hold an analog value in one cell, and then deliver it to the next, and the next, controlled by clock pulses allowing electronic control over delay times. This handing of the signal down the line from one cell to the next recalled early methods of fire fighting where buckets of water would be handed down a line from one person to the next, earning it the name “bucket-brigade.” The delay times were limited, as was the audio quality. However, they had a certain color to them that some still find appealing. You can still buy analog delays in the form of guitar pedals from Moog Music and Ibanez.

Digital technology revolutionized music production. It made longer delay times, lower noise, and increased control and versatility readily available for reasonable prices. Modern digital delays offer several controls, including delay time, usually measured in milliseconds (ms), or thousandths of a second. Also included is a feedback or regeneration control, allowing multiple echoes. Balance lets you mix the delayed signal with the direct sound. Delay times below about 40-50 ms aren’t heard as discrete echoes, but rather as part of the direct sound. Doubling is the effect of a delay below 40-50 ms that gives the illusion of more than one sound source. Also included in modern delays is a modulation depth and rate control. These controls used in conjunction with short delay times below 40 ms allow you to create other time-based effects, including flanging, phasing, and chorusing. The modulation depth varies the delay time constantly, and as such, varies the pitch of any delayed signals still in memory. This causes the pitch of the echoes to be slightly higher or lower than the direct sound’s pitch, and mixed with the direct sound, it provides a rich, fat, and perhaps swooshing effect to the sound. The greater the depth, the greater the variation in delay times and pitch. The greater the rate, the faster those variations happen.

Many people don’t realize the various effects that delays can create beyond slapback echo. You can send delay returns into other effects, like reverb or EQ, for additional creative possibilities. These effects can greatly enhance production value, or can clutter a mix or sound “cheesy” if overused. Arming yourself with information and experimenting to gain experience will ensure that you get the most from your delay effects.

Some classic digital delays:
t.c. electronic 2290: recently discontinued, about $1,000 used, has tap tempo entry


Lexicon PCM-42: discontinued; about $1,000 used, but now availableas a plug-in for $149

Vintage analog tape delay:
Echoplex (Maestro): $500-$1,000

Currently produced analog Delays:
Moog Music MF-104Z: $689

Ibanez AD-9: $169

Some affordable digital delays:
t.c. electronic D-two: $499; dual engine with tap tempo and up to 10 seconds of delay time


Lexicon MX200: $199; also has reverb and other effects
(Expected street prices quoted)

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