Constant power balance controls for stereophonic and quadraphonic sound systems

• US 4,063,032 A
• Filed: 03/16/1976
• Issued: 12/13/1977
• Est. Priority Date: 03/16/1976
• Status: Expired due to Term

• Current Assignee: John C. Bogue, Wesley Ruggles Jr
• Original Assignee: John C. Bogue, Wesley Ruggles Jr
• Inventors: Willcocks, Martin Edmund George
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US05/667,455
• Time in Patent Office: 637 Days
• Field of Search: 179/1 GQ, 179/1 G, 179/1 VL, 179/15 BT, 179/100.1 TD, 179/100.4 ST
• US Class Current: 381/19
• CPC Class Codes: H04S 7/00 Indicating arrangements; Control arrangements, e.g. balance control
• CPC Class Codes: H04S 7/302 Electronic adaptation of stereophonic sound system to listener position or orientation H04S7/301 takes precedence

Abstract

Constant power balance control systems for stereophonic and quadraphonic sound systems are disclosed. Three different embodiments of the invention are disclosed. The first embodiment is a resistive network having a plurality of fixed resistors and a linear potentiometer. The second embodiment is a solid state circuit having four pairs of transistors. The transistors of each transistor pair are chosen to have characteristics such that for the same base-to-emitter voltage, the collector currents of the transistors of each pair satisfy a given ratio. The third embodiment is a combination of the first two embodiments. The third embodiment provides a comprehensive quadraphonic gain and balance control system.

Claims

1. In apparatus for reproducing on two loudspeaker the audio signals contained in two independent channels, a balance control circuit comprising:

first and second differential voltage-to-current converters each having a pair of input terminals to which the respective one of said first and second audio input signals is applied differentially, and a pair of output terminals, and being operative to provide at its output terminals a pair of output currents having equal direct current components and equal signal current components in antiphase,

first, second, third and fourth current-splitting means, each having an input terminal, a first and a second output terminal, a first and a second control terminal, and being operative to split any current flowing through its input terminal into a first output current at its first output terminal and a second output current at its second output terminal in a predetermined constant ratio dependent on the voltage applied between its first and second control terminals,

the input terminals of said first and second current-splitting means being connected respectively to the first and second output terminals of said first differential voltage-to-current converter and the input terminals of said third and fourth current-splitting means being connected respectively to the first and second output terminals of said second differential voltage-to-current converter,

first, second, third and fourth load resistors respectively connected between said first output terminal of said first, second, third and fourth current-splitting means and a common signal ground terminal, said second output terminal of each of said first, second, third and fourth current-splitting means being connected directly to said common signal ground terminal,

said first control terminals of said first and second current-splitting means being connected together with said second control terminals of said third and fourth current-splitting means to a common first control terminal, and

said second control terminals of said first and second current splitting means being connected together with said first control terminals of said third and fourth current-splitting means to a common second control terminal,

the first output audio signals from the balance control circuit being taken differentially between said first output terminals of said first and second current-splitting means and the second output audio signal being taken differentially between said first output terminals of said third and fourth current-splitting means,

each of said current-splitting means being configured to split the input current applied to its input terminal into two output currents in a ratio determined by the control voltage applied between its first and second control terminals, the fraction of the input current which appears at the first output terminal being approximately equal to (1 + x)/(1.414 + 0.586x) where x is the ratio of the control voltage applied between the first and second control terminals to the maximum value of control voltage which may be applied thereto, and x may be varied between -1 and 1 by varying the control voltage,

the whole circuit being operative to provide at its differential outputs first and second audio output signals which are identical in content to said first and second input signals respectively but are amplified or attenuated by different factors depending on the applied control voltage such that if equal input signal voltages are applied to said first and second voltage-to-current converters the r.m.s. sum of the output signal voltages is maintained substantially constant irrespective of the applied control voltage.

2. Apparatus according to claim 1 in which each of said current-splitting means comprises first and second transistors having different characteristics such that for equal base-to-emitter voltages their collector currents are in the ratio of 2.414 to 1, the collector of said first transistor being connected to said first output terminal and the collector of said second transistor being connected to said second output terminal, the bases of said first and second transistors being connected each to the anode of a diode, the cathodes of both diodes being connected to a fixed voltage and the anodes of said diodes being driven by the two outputs of a differential voltage-to-current converter whose input terminals are said first and second control terminals of said current-splitting means.

3. Apparatus according to claim 1 in which said voltage-to-current converter and said two diodes are common to both current-splitting means and are connected to vary the balance between said first and second audio signals.

4. Apparatus according to claim 6 in which said voltage-to-current converter and said two diodes are common to both current-splitting means and are connected to vary the balance between said first and second audio signals.

5. In apparatus for reproducing on four loudspeakers the audio signals contained in four independent channels, a comprehensive gain and balance control circuit comprising:

first, second, third and fourth input terminals to which said four audio signals are respectively applied,

a first balance circuit connected to balance said first and second signals,

a second balancing circuit connected to balance said third and fourth signals,

a third balancing circuit connected to balance said first and third signals,

a fourth balancing circuit connected to balance said second and fourth signals, said third and fourth balancing circuits being connected to a single means for generating first and second control voltages,

said means for generating said first and second control voltages being connected to a variable d.c. voltage,

the whole circuit including a first balancing potentiometer connected to the first balancing circuit and operative to vary the balance between said first and second channels, a second balancing potentiometer connected to the second balancing circuit, and operative to vary the balance between said third and fourth channels, a third balancing potentiometer forming part of said means for generating said first and second control voltages and operative to vary the balance between said first and second control voltages, and a gain control potentiometer, operative to provide a variable d.c. voltage to the d.c. input terminal of said means for generating said first and second control voltages thereby varying the gain of all four channels simultaneously without affecting the balance between any pair of the four channels.