GRAPHIC BALANCER

Abstract: A graphic balancer having level adjusting means (oper­ ation amplifiers 1L, 1R, resonance circuits 2L, 2R, volumes 3L, 3R) for each of the bands to increase the level of voice signals of one channel between the stereophonic two channels div­ ided into a plurality of bands, and to correspondingly dec­ rease the level of the other channel, so that the position of acoustic image can be changed for each band. An embodi­ ment of the invention is shown, in which the graphic balancer and the graphic equalizer can be switched to operate.

Description: The present invention relates to a graphic balancer having two channels. A graphic balancer as depicted in Fig. 1 is known from JP-U-59/33400. It comprises operational amplifiers 1L and 1R and resonators 2L and 2R for right and left channels. The resonators 2L and 2R are connected to movable terminals of volume controls 3L and 3R whose middlepoints are grounded. The volume controls 3L and 3R are connected between output terminals and negative feedback input terminals of the operational amplifiers 1L and 1R. The movable terminals of the volume controls 3L and 3R are syn­ chronously moved in opposite directions. Therefore, when the volume control 3L in the left channel is moved to the left to increase the output gain, the movable terminal of the volume control 3R in the right channel is moved to the right, thereby decreasing the output level. US-A-3,566,294 shows in its Fig. 14 a similar graphic balancer, however with the possibility to vary volume in a plurality of individual bands. Increase or decrease of the gain is carried out separately for each of the frequency bands or simultaneously for all of them. It is the object of the present invention to provide a graphic balancer having a broader variety of usage. The graphic balancer of the present invention comprises a) first and second channel operational amplifiers, each having an input terminal, an output terminal and a feedback terminal, b) a first volume control having a movable terminal, two end terminals and a center tap, said two end terminals being connected between the feedback and output terminals of said first channel operational amplifier with said tap being connected to a reference point, c) a second volume control having a movable terminal, two end terminals and a center tap, said tap being connected to said reference point, d) first and second resonators, respectively, connected between the movable terminals of said first and second volume controls and said reference point, and e) switching means for selectively connecting said second volume control in such a way that the connection of two end terminals thereof are interchangeable between the feedback and output terminals of said second channel operational amplifier so as to select a specific equalizer characteristic or a balance characteristic. Due to said switching means, the graphic balancer can be used also as a graphic equalizer. Switching between the two modes is provided by only operating the switching means. No additional components besides the switching means are necessary to provide the two modes. In case that the balancer/equalizer comprises volume controls for several bands, there may be a single switching means for changing the mode within all bands or there may be a separate switching means for each band. The invention will now be explained by two embodiments according to circuit diagrams of Fig. 2 and 3. The figures show: Fig. 1: a circuit diagram of a graphic balancer as known from JP-U-59/33400; Fig. 2: a circuit diagram of a graphic balancer/equalizer having a single, common switching means for a plurality of bands; and Fig. 3: a circuit diagram similar to the diagram of Fig. 2, however, with separate switching means for each of a plurality of bands. Fig. 2 shows a first embodiment wherein a graphic equalizer and a graphic balancer employs a common circuit to be switched over for use. Each channel is arranged such that the basic circuits shown in Fig. 1 are connected in parallel by the number of divided bands. In one channel (the left channel in Fig. 2), both terminals of each volume 3L connected in parallel are connected between the negative feedback input terminal of the operational amplifier 1L and one terminal of the output resistor 5L through interlinked switches 6a and 6b so as to be inversely (interchangeably) connected. When the switches 6a and 6b are switched to the side of an equalizer EQ, the volume controls 3L and 3R in the left and right channels are moved in the same direction, thereby simultaneously controlling increase or decrease of the output levels of the right and left channels. When the switches 6a and 6b are switched to the side of a balancer BL, the volume controls 3L and 3R are moved in the opposite directions to increase the output level of one channel and decrease that of the other at each band, thereby synchronously performing this balancing operation. Fig. 3 shows a second embodiment wherein the equalizer and the balancer can be switched over in each band. More specifically, there are provided switches 7a and 7b for inverting both terminals of each volume 3L in the left channel and connecting them to the operational amplifier 1L in individual bands. Therefore, the equalizer function or the balancer function can be selected in any band. Note that in the above embodiments, a balanced (or an unbalanced) condition is displayed as a graph (a compensation curve) along the frequency axis by the position of control knobs or by a display means. Effect of the Invention.

Claims: 1. A graphic balancer comprising: a) first and second channel operational amplifiers (1R, 1L), each having an input terminal, an output terminal and a feedback terminal, b) a first volume control (3R) having a movable terminal, two end terminals and a center tap, said two end ter­ minals being connected between the feedback and output terminals of said first channel operational amplifier with said tap being connected to a reference point, c) a second volume control (3L) having a movable terminal, two end terminals and a center tap, said tap being con­ nected to said reference point, and d) first and second resonators (2R, 2L),respectively, connected between the movable terminals of said first and second volume controls and said reference point, characterized by e) switching means (6a, 6b; 7a, 7b) for selectively connecting said second volume control (3L) in such a way that the connection of two end terminals (EQ, BL) thereof are interchangeable between the feedback and output terminals of said second channel operational amplifier (1L) so as to select a specific equalizer characteristic or a balance characteristic. 2. A graphic balancer according to claim 1, characterized in that the respective end terminals of a plurality of second volume controls (3L) are connected in series and that said switching means (6a, 6b) switches between the common end terminals (Fig. 2). 3. A graphic balancer according to claim 1, characterized in that a separate switching means (7a, 7b) is provided for each second volume control (3L) in a plurality of bands (Fig. 3).

Inventors: IDE, TERUHISA, KINOSHITA, TSUTOMU, OHTSU, MASAHIRO
Applicants: SONY CORPORATION
Application year: 1986
Main classification: H04S7
IPC codes: H03G5, H04S7