Digital delay system for audio signal processing

Claim 2

A digital delay system for audio signal processing, adapted for use in sound reinforcement in auditoria and other applications, for use with an audio signal source and at least one audio reproducer, comprising: an analog-digital converter, coupled to an audio signal source, for converting an analog audio signal received from the source into a digital data signal; a digital data store, coupled to said analog-digital converter, for recording said digital data signal; output means for said digital data store, for reading the digital data signal from the store at any one of a plurality of different delay intervals subsequent to recording; at least one digital-analog converter, connected to said data store output means, for developing a delayed representation of the analog audio signal; and means coupling said digital-analog converter to said audio reproducer to develop a delay audible reproduction of the initial analog audio signal.

Claim 3

A digital delay system for audio signal processing, according to claim 1, in which said analog-digital converter is a delta modulator and which includes a plurality of digital-analog converters, each coupled to at least one audio reproducer.

Claim 4

A digital delay system for audio signal processing, according to claim 2, in which each digital-analog converter comprises an integrator having operating characteristics substantially the same as a main integrator circuit included in said delta modulator.

Claim 5

A digital delay system for audio signal processing, according to claim 1, in which said analog-digital converter is a delta modulator comprising: a high-gain comparator amplifier having an inverting input and a non-inverting input, and an output; means for applying an analog signal to the inverting input of said comparator amplifier a sampling gate having an input connected to the output of said comparator amplifier and having a main output and an auxiliary output; the inverting input of said comparator means for applying a high-frequency sampling signal to said sampling gate to actuate said gate between said alternate outputs; an integrating negative feedback circuit connected between said main sampling gate outputs and said inverting input of said comparator amplifier, for developing a replica signal and for applying that replica signal to the inverting input of the comparator amplifier in bucking relation to said analog signal, for amplitude comparison therewith; and an auxiliary feedback circuit, connected between the auxiliary output of the sampling gate and the non-inverting input of the comparator amplifier, for affording a self-bias reference for the comparator amplifier and effectively eliminating any offset voltages generated in the comparator amplifier and the sampling gate.

Claim 6

A digital delay system for audio signal processing, according to claim 1, in which said analog-digital converter is a pulse code modulator and which includes a plurality of digital-analog converters, each coupled to at least one audio reproducer.

Claim 7

A digital delay system for audio signal processing, according to claim 1, in which said digital data store comprises an integrated circuit shift register and said output means comprises a series of spaced taps at different stages along that register.

Claim 8

A digital delay system for audio signal processing according to claim 6, including means for applying synchronized clock signals to said analog-digital converter and to the shift circuits of said shift register to control the sampling rate for digital conversion and the rate of transfer of data along the shift register, respectively, with provisiOn for adjusting the clock signal frequencies to adjust the time delays at said taps on the shift register.

Claim 9

A digital delay system for audio signal processing, according to claim 1, in which said digital data store comprises a sonic delay line.

Claim 10

A digital delay system for audio signal processing, according to claim 8, in which said delay line is operated in a recirculation mode, with the data recorded therein recirculated a fixed number of cycles and with a predetermined number of data bits replaced in each cycle.