digital delay line

There are several applications for a circuit that can delay digital signals, the Digital Reverberation Unit described in the recent May issue of Elektor being but one example. The most common method of delaying digital signals is to use a shift register. The circuit shown in figure l may therefore appear somewhat unusual, in that the two most prominent components are not shift registers but Random Access Memories (RAMs; IC2 and IC3). In this circuit, the digital data are stored in the RAMs for the duration of the desired delay period and then recalled and presented at the `delay data` output. Since the 1024-bit RAMs used here (type 2102) are relatively inexpensive, there is no need to skimp on memory space - if longer delay times are desired, the circuit can easily be extended as will be described later.