Convertible amplifier system for single and multiple signal sources
United States Patent Klauck 1 Apr. 29, 1975 CONVERTIBLE AMPLIFIER SYSTEM FOR 3.376.388 4/1968 Reifi&#39;in v V v 179/1 A SINGLE AND MULTPLE SIGNAL 3.562.660 2/l97l Pease.-.=;.;-.=..= .;v=-..;.1.1.v.= 330/30 D [75] lnventor: David Edward Klauck, Bridgman. Primary Exum;ner-;Kath|een Claffy Assistant Examiner Tommy P. Chin [73] Assignee: GTE Sylvania Incorporated. Al F- m OMalleyl St f d C Thomas H; Buffton; Cyril A; Krenzer [22] Filed: May 23, 1973 [57] ABSTRACT PP 3631173 A convertible am lifier system includes a pair of 0 erational amplifier means each having oppositely-phased [521 u.s. c1. 179/1 A; 179/1 G input terminals 3 of loudspeakers and a Switch- [51] Int Cl 03g 1 ing means for selectively coupling each one of the op- [58] Field of Search 179/1 1 G1 330/30 D. erational amplifier means to a signal source and to a 330/30 R loudspeaker to provide a multiple signal response and for connecting the output of one to the input of the [56] References Cited other and the outputs of both operational amplifier r means to a loudspeaker to effect phase inverted unity UNITED STATES PATENTS I H G gain of the other operational amplifier and a single sig- 3.o2e.3711 3/1962 Finest. 179 I 3.213.198 10/1965 Claras; 179/1 0 responsl e Sys em 3372 342 3/1968 Reiffin 9 Claims, 1 Drawing Figure 5 a it. a a 777 or 3 7 s .m l A b C I DIFFERENTIAL PUSH&#39; PULL AMPLIFIER AMPLIFIER n r w wm/j 3\HW. v I  
 DIFFERENTIAL PUSH PULL 5/ AMPLIFIER AMPLIFIER CONVERTIBLE AMPLIFIER SYSTEM FOR SINGLE AND MULTIPLE SIGNAL SOURCES BACKGROUND OF THE INVENTION The present invention relates to a convertible amplifier system suitable for use with signals from a single or multiple source. The system provides either monophonic or stereophonic response in accordance with either single or multiple signal sources. Moreover, the system is especially suited to the popular four-channel techniques of sound reception and reproduction.  
  Generally, amplifier systems convertible to reception from either single or multiple signal sources to provide monophonic or stereophonic sound reproduction utilize output stages connected either single-ended or in push-pull. In other words, a common technique utilizes a pair of channels each having a driver stage coupled to a signal source and to an output stage connected to a loudspeaker. Thus, stereophonic sound reproduction is effected. For monophonic sound reproduction, a single signal source is usually applied to a driver stage which is coupled to the second driver stage and, in turn, connected to push-pull connected output stages. Thus, a single-ended system is converted to a push-pull system when stereophonic reproduction is shifted to monophonic sound reproduction.  
  Although the above-mentioned technique has been and still is employed in numerous high fidelity sound systems, it has been found that there are systems wherein such a technique leaves something to be desired. For example, four-channel sound systems tend to require a relatively complex and expensive switching arrangement when the above-described apparatus is employed.  
 OBJECTS AND SUMMARY OF THE INVENTION An object of the present invention is to provide an enhanced sound reproduction system adaptable to single and multiple channel sound reproduction. Another object of the invention is to provide an improved convertible amplifier system for single and multiple channel sound reproduction. Still another object of this invention is to improve the capability for reproducing signals from single and multiple signal sources. A further object of the invention is to reduce the complexity of switching between single and multiple signal sources and reproduction capabilities.  
  These and other and further objects, advantages and capabilities are achieved in one aspect of the invention by a convertible amplifier system having at least one pair of loudspeakers and at least one pair of operational amplifier means with a switching means for selectively coupling each one of said pair of operational amplifier means to a signal source and to a loudspeaker for multiple signal response and for decoupling an amplifier means from a signal source, coupling the output of one amplifier means to the input of the other amplifier means, and for interconnecting the output of both amplifier means by way of a loudspeaker to provide a single signal response.  
 BRIEF DESCRIPTION OF THE DRAWINGS The sole FIGURE is a diagrammatic illustration, in block and schematic form, of a convertible amplifier system.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in conjunction with the accompanying drawing.  
  In the drawing, a first signal source 3 is coupled to an operational amplifier means 5 which includes a differential amplifier stage 7 and a push-pull amplifier stage 9. The differential amplifier stage 7 has a first input terminal 11 coupled to the first signal source 3 and via series connected resistors 13 and 15 to circuit ground. An oppositely-phased second input terminal 17 of the differential amplifier stage 7 is coupled by a capacitor 19 to the junction of the series connected resistors 13 and 15. The output of the differential amplifier stage 7 is coupled to the push-pull amplifier stage 9 which has an output coupled by a resistor 21 to the second input terminal 17 of the differential amplifier stage 7 and directly connected to a loudspeaker 23.  
  A second signal source 25 is selectively coupleable to another operational amplifier means 27 having a differential amplifier stage 29 and a push-pull amplifier stage 31. The other differential amplifier stage 29 has a first input terminal 33 connected to circuit ground via series connected resistors 35 and 37 and selectively coupled to the second signal source 25. An oppositely-phased second input terminal 39 of the differential amplifier stage 29 is coupled by a capacitor 41 to the junction of the series connected resistors 35 and 37. The output of the differential amplifier stage 29 is coupled to the input of the push-pull amplifier stage 31 which has an output coupled by a resistor 43 to the second input terminal 39 of the differential amplifier stage 29.  
  A switching means 45 includes a plurality of ganged contacts. A first contact 47 is connected by a resistor 48 to the junction of the series connected resistors 35 and 37 and via the capacitor 41 to the oppositely-phased second input terminal 39 of the differential amplifier stage 29. Thus, the second input terminal 39 is selectively coupled by the first contact 47 to circuit ground or to the output of the push-pull amplifier stage 9 of the operational amplifier means 5.  
  A second contact 49 of the switching means 45 selectively couples the first loudspeaker 23 to circuit ground or to the output of the push-pull amplifier stage 31 of the other operational amplifier means 27. A third contact 51 of the switching means 45 selectively couples the output of the push-pull amplifier stage 31 to a loudspeaker 52 connected to circuit ground or to the first loudspeaker 23 via the second contact 49 of the switching means 45. Moreover, a fourth contact 53 of the switching means 45 provides for the selective coupling of the first input terminal 33 of the differential amplifier stage 39 to circuit ground or to the second signal source 25.  
  As to operation, each of the contacts, 47, 49, SI, and 53 of the switching means 45 has a pair of contact points marked N for normal or multiple signal response and B for bridge or a single signal response. Moreover, the contacts 47, 49, 51 and 53 are ganged&#34; to provide selective selection of normal or bridge-type operation.  
  Assuming multiple signals or a signal is available from each one of the signal sources, 3 and 25 respectively. The switching means 45 would be positionally located in the N or normal position. A signal from the first signal source 3 would be applied to the first input terminal 11 of the differential amplifier stage 7 of the operational amplifier means 5. This signal would be transmitted via the push-pull amplifier stage 9 to the loudspeaker 23 coupled to circuit ground by the second contact 49. A signal from the second signal source 25 would be coupled via the fourth contact 53 to the first input terminal 33 of the differential amplifier stage 29 of the other operational amplifier means 27. The output of the differential amplifier stage 29 is applied to the push-pull amplifier stage 31 and via the third contact 51 to another loudspeaker 52 coupled to circuit ground. Moreover, the junction of the series connected resistors 35 and 37 would be coupled via the resistor 48 and first contact 47 to circuit ground.  
  Thus, a signal from each one of the signal sources 3 and 25 is coupled via an operational amplifier means, and 27 respectively, to a loudspeaker 23 and 52. Therefore, each signal channel exhibits an individual response capabilityv Assuming a single signal response is to be effected, the contacts 47, 49, 51, and 53 of the switching means 45 are positioned at the bridge or B location for single signal response. A signal from the first signal source 3 is applied to the first input terminal 11 of the differential amplifier stage 7, to the push-pull amplifier stage 9, and to the loudspeaker 23.  
  Also, the output from the push-pull amplifier stage 9 of the operational amplifier means 5 is applied via the first contact 47 of the switching means 45, resistor 48, and capacitor 41 to the oppositely-phased second input terminal 39 of the differential amplifier stage 29 of the other operational amplifier means 27. In turn, the output of the differential amplifier stage 29 is applied to the push-pull amplifier stage 31 and via the second contact 49 to the loudspeaker 23. Moreover, the third contact 51 is positioned to disconnect the loudspeaker 52 while the fourth contact disconnects the second signal source 25 and grounds the first input terminal 33 of the-differential amplifier means 29.  
  Thus, it can be seen that a single signal source is coupled by way of an operational amplifier means 5 to a loudspeaker 23. Also, the output of the operational amplifier means 5 is coupled to the oppositely-phased second input terminal 39 of the other operational amplifier means 27 which is coupled to the same loudspeaker 23. Thereupon, the other operational amplifier means 27 serves as a unity-gain inverting amplifier having an output 180 degrees out of phase with the one operational amplifier means 5.  
  Additionally, it can be shown that the voltage output of the other operational amplifier means 27 is equal to but oppositely-phased from the voltage output of the one operational amplifier means 5.  
  21 5 Thus, the potential delivered to the loudspeaker R23 for single signal reception is:  
 Power 23) 2s (2V21)2/R23 4V272/R23 Therefore, the theoretical power applied to a loudspeaker for single signal reception is four times greater than the power provided at the same loudspeaker when multiple signal response is effected.  
  4 As representative but in no way limiting the invention, the following exemplary component values are provided:  
 Rl3. R21. R35. R43. R48 10 k ohms R15. R37 470 ohms C19. C41 220 t R23. R52 8 ohms Thus, there has been provided a unique convertible amplifier system adapted to single and multiple signal sources to provide single or multiple channel sound response. The system includes a switching capability which is simple and inexpensive of components and assembly. Moreover, the system provides a push-pull output capability for both single and multiple signal response with enhanced power available when a single signal source is employed.  
  While there has been shown and described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.  
 What is claimed is:  
  l. A convertible amplifier system for single and multiple signal sources comprising:  
 a pair of loudspeakers;  
 a pair of operational amplifier means, each having oppositely-phased input terminals; and  
 switching means for selectively coupling each one of said pair of operational amplifier means to one of said pair of loudspeakers and to a signal source to provide multiple signal response and for coupling the input terminal of one operational amplifier means to a signal source, the input terminal of the other operational amplifier means to a potential reference level, the oppositely-phased input terminal of the other to the output of the one operational amplifier means, and the outputs of the operational amplifier means to a loudspeaker to provide a &#39;single signal response.  
  2. The convertible amplifier system of claim 1 wherein each one of said operational amplifier means includes a driver stage having oppositely-phased input terminals.  
  3. The convertible amplifier system of claim 1 wherein each one of said operational amplifier means includes a push-pull connected output stage.  
  4. The convertible amplifier system of claim 1 wherein the power delivered to a loudspeaker for a single signal response is in the range of about 4:1 when compared to the power delivered to a loudspeaker for multiple signal response.  
  5. The convertible amplifier system of claim 1 wherein said switching means is in the form of a ganged multiple contact switch.  
  6. In single and multiple signal source apparatus, a convertible amplifier system comprising:  
 at least two loudspeakers;  
 at least two operational amplifier means each having oppositely-phased signal input terminals; and switching means for selectively coupling said amplifier means to said loudspeakers and to said signal sources, said switching means including ganged switches formed for coupling each one of said operational amplifier means to a signal source and to a loudspeaker to provide a multiple signal response 8. The convertible amplifier system of claim 6 wherein the power delivered to a loudspeaker in single signal and in multiple signal response is in the ratio of about 4:1.  
  9. The convertible amplifier system of claim 6 wherein the output of one of said amplifier means is coupled to an oppositely-phased input of the other amplifier means for single signal response.