Coded data generation or conversion – Analog to digital conversion followed by digital to analog...
Reexamination Certificate
2000-05-16
2001-04-17
Young, Brian (Department: 2819)
Coded data generation or conversion
Analog to digital conversion followed by digital to analog...
C381S018000, C704S267000
Reexamination Certificate
active
06218971
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to mixers, more particularly to a multichannel digital mixer suitable for handling audio signals, and still more particularly to such a mixer designed explicitly for cascade connection with another mixer of identical make, beside being capable of use as an independent unit. The invention also pertains to a system of two such multichannel digital mixers in cascade connection.
Sixteen-input mixers are in widespread use for mixing audio signals from as many individual microphones. Audio engineers are, however, not always satisfied with sixteen channels but sometimes desire more channels. Conventionally, for fulfillment of this desire, it has been practiced to connect two sixteen-input mixer units of identical make in cascade mode by means of cables in cases where a more-than-sixteen-input mixer is not available. The cascaded mixer system provides a total of thirty-two inputs.
The cascading of two analog mixer units is easy if each one is fabricated with that mode of use in mind, complete with a set of cascading inputs in addition to the regular signal inputs. One mixer unit has its cascading inputs left unused but has its combined signal outputs cabled to the cascading inputs of the other mixer unit.
The audio outputs from microphones or the like are directed into the respective input circuits of the two mixer units thereby to be variously conventionally processed and routed to provide, for instance, left and right “stereo” signals, four-channel “group” signals for monitoring, and two-channel “effect” signals for echo and other acoustic effects. The output signals from the first mixer unit are directed into the cascading inputs of the second unit thereby to be combined with like signals. The combined signals are produced from the outputs of the second mixer unit.
Recently, with the advent and increasing commercial acceptance of compact disks and other digital audio signal sources, analog mixers are being superseded by digital mixers. Being functionally equivalent to analog mixers, digital mixers also lend themselves to cascade connection, provided, however, that each unit is furnished with digital output circuits and digital input circuits for cascading.
An objection to the prior art digital mixer units designed for cascade connection is that the provision of many such digital output circuits and input circuits have rendered each unit very costly. The mixer system constituted of two such prior art digital mixer units in cascade connection is itself objectionable, too, because of the necessity for operating the control boards of both units.
SUMMARY OF THE INVENTION
The present invention aims at the provision of a digital mixer unit explicitly designed for use either singly or in cascade connection with another unit of like construction.
Another object of the invention is to attain the first recited object by making the construction of each mixer unit, as well as interconnections between two such units, as simple as feasible without impairment of their intended functions either as independent mixers or as a cascade mixer system.
Still another object of the invention is to make the cascade connection of two mixer units operable on one unit only.
Briefly summarized in one aspect thereof, the present invention provides a multichannel digital mixer unit for use either singly or in cascade connection with another mixer unit of identical make. The mixer unit comprises: (a) a plurality of analog inputs for inputting as many analog signals to be mixed; (b) at least one digital input for inputting a digital output signal from a second mixer unit of identical make if such a unit is connected in cascade with the instant unit; (c) a plurality of analog-to-digital converters connected one to each analog input for digitizing the input analog signals; (d) a digital signal processor connected to the digital input and the analog-to-digital converters for producing a plurality of digital output signals by mixing the digital input signal, if any, from the second mixer unit and the outputs from the analog-to-digital converters; (e) a plurality of digital-to-analog converters connected to the digital signal processor for converting the digital output signals therefrom into analog signals; (f) a plurality of analog outputs connected one to each digital-to-analog converter for putting out the analog output signals therefrom; (g) at least one digital output connected to the digital signal processor for putting out at least one of the digital output signals therefrom for application to the digital input of the second mixer unit if such a unit is cascaded with the instant unit; (h) operating means for manually inputting instructions indicative of instructions to be performed by the digital signal processor on the signals input thereto; (i) control means connected between the operating means and the digital signal processor for causing the latter to process the input signals according to the instructions from the operating means; and (j) control input/output means for connecting the control means to like control means of the second mixer unit if such a unit is cascaded with the instant unit, in order to permit control of both mixer units by either mixer unit.
Another aspect of the invention concerns a digital cascade mixer system comprising two digital mixer units, each constructed as in the foregoing, in cascade connection with each other. The two mixer units are cascaded by connecting the digital output or outputs of a first unit to the digital input or inputs of a second unit, the digital output or outputs of the second unit to the digital input or inputs of the first unit, and by interconnecting the control input/output means of both unit&
In the preferred embodiment to be disclosed subsequently, two sixteen-channel mixer units, each constructed as in the summary above, are cascaded to provide a thirty-two-channel mixer system for processing as many analog audio outputs from individual microphones. Only four selected outputs (e.g. “group” signals) from the digital signal processor of one mixer unit are directed to the digital inputs of the second unit, therein to be mixed with like signals. Another four selected outputs (e.g. two “stereo” signals and two “effect” signals) from the digital signal processor of the second unit are directed to the digital inputs of the first unit, also therein to be mixed with like signals.
The mixing of thirty-two input audio signals is possible in the above described manner even though the two cascaded mixer units are each greatly simplified in construction compared to the noted prior art mixers designed for cascading.
For even simpler connection of the two mixer units according to the invention, it is recommended that the desired digital audio signals be transferred between the two mixer units by multiplex transmission. Each mixer unit incorporates two digital output circuits in the preferred embodiment, each for multiplexing two outgoing digital audio signals, and two digital input circuits for demultiplexing the two incoming digital audio signals into four. Only half as many audio signal paths are then required between the two mixer units as when they are sent separately.
The present invention also proposes the interconnection of the control sections of both mixer units, preferably by means meeting the standard MIDI interface criteria. The cascade mixer system will then become operable on one mixer unit by establishing master-slave relationship between the two units.
The above and other objects, features and advantages of this invention and the manner of achieving them will become more apparent, and the invention itself will best be understood, from a study of the following description and attached claims, with reference had to the accompanying drawings showing the preferred embodiment of the invention.
REFERENCES:
patent: 5794201 (1998-08-01), Nejime et al.
patent: 6016114 (2000-01-01), Liu et al.
patent: 6037993 (2000-03-01), Easley
Nguyen John
Teac Corporation
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
Young Brian
LandOfFree
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