GB1350371A - Four channel audio systems - Google Patents

Abstract

1350371 Variable resistance controls for amplifiers; quadraphonic volume controls; quadraphonic systems MOTOROLA Inc 19 April 1971 [23 April 1970] 27173/71 Headings H3Q H4J and H4R [Also in Division H1] In a four channel audio system including a variable resistance device 32 for controlling the balance of sound from the four channels the variable resistance device includes a control space 22 and a control knob 24 operable about the control space to operate the variable resistance device so as to change the balance of sound from the four channels. The movable contact 30 of the control knob 24 is mounted by a shaft 26 on a non-conductive plate 28 which is slidable within walls 14a, 14b of an eight track tape cartridge player (10, Fig. 1, not shown). By moving knob 24 in any direction allowed by the sliding plate 28 within a control space 22 the contact 30 can be adjusted to any position on the resistance element 32. The control space 22 may alternatively be hemi-spherical. This allows balance to be obtained between four loud-speakers, such as positioned at four corners within a car, by the corresponding adjustment of four resistors (32a-32d, Fig. 6, not shown) formed by the four sections A-30, B-30, C-30 and D-30 of the resistance device connected to four audio amplifier channels (A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, D<SP>1</SP>). The plate 28 is frictionally held in its preselected position by spring pressed members 31a. Volume control may be adjusted by a central knob 24a which has a movable contact 42 slidable over an arcuately shaped resistance track 40. Tone control may be adjusted by rotating knob 24b which has a contact 46 slidable over an arcuately shaped resistance track 48. The volume control (40a, Fig. 6, not shown) and tone control 48a are connected to each amplifier channel (A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, D<SP>1</SP>). Printed circuit connections from the ends of the resistance tracks 40, 48 of the volume and tone controls are connected to leads 50 and the connection of the shaft 26 to a reference potential may be via a printed circuit conductor within the plate 28. The resistance element 32 may be formed, as by the slots 36a-36d, to vary the electrical characteristic, such as exponentially, from one location to another location of contact 30.