US1914629A - Electrical network - Google Patents

Description

June 20, 1933. AGUlRRE 1,914,629

ELECTRICAL NETWORK Filed Oct. 28, 1950 2 Sheets-Sheet l NETWORK INVENTOR MAXIMO AGUIRRE June 20 1933. M. AGUERRE 199141529 ELECTRICAL NETWORK Filed Oct. 28, 1930 2 Sheets-Sheet 2 d BASS TREBLE PASS PASS l1 9f u 5 6 8 a CONTROL CQNTROL i 7 ID WU g 2 NETWORK INVENTQR:

MAXIMO AGUIRRE ATTORNEY.

Patented June 2t), 1933 PATENT OFFICE IVIAXIMO AGUIRRE, OF COTATI, CALIFORNIA ELECTRICAL NETWORK Application filed. October 28, 1930.

This application relates generally to electrical networks such as are utilized for repeating electrical current variations of voice frequencies. It has particular application to 55 vacuum tube or electron relay amplifier systems, such as are utilized in connection with broadcast radio receivers electrical phonographs, talking moving picture apparatus, and the like, where the quality of the reproduced or translated sound is of importance.

In audio frequency amplifying systems it is common for the overall characteristic performance curve to drop off for certain frequencies within th range of audibility, due

5 to various imperfections. As a result the translation of the current variations into sound does not give faithful reproduction. In other systems in which the amplifiers may have high fidelity, the translated sound may not give proper tonal efiects due to imperfections in the input modulations, as for eX- ample where microphone or sound record does not have high fidelity with respect to the original sound waves, or where a loud speaker or other translator connected to the output is defective.

It is an object of the present invention to devise an electrical network and method of utilizing the same whereby the overall characteristics of an audio frequency amplifying system with which the invention is employed, can be modified or compensated to secure better quality reproduction. I It is a further object of the invention to devise an electrical network of the above character having provision whereby the normal repeatin characteristics of the amplifying system with which the invention is employed can be modified by compensating gains for certain frequencies, which are at the will of the operator.

It is a further object of the invention to eliminate or minimize motor boating in an electrical network of the above character.

5 Further objects of the invention will ap- Serial No. 491,703.

Fig. 1 is a circuit diagram illustrating an electrical network incorporating the present invention.

Fig. 2 is a view illustrating the network of Fig. 1 diagrammatically.

Fig. 3 illustrates the electrical network of Fig. 1 applied to an audio frequency amplifying system having transformer coupling.

Fig. i is a circuit diagram illustrating the electrical network of Fig. 1 applied to an audio frequency amplifying system having resistance coupling.

The nature of the invention can be best understood by referring first to diagrammatic *ig. 2. In this instance I have indicated an electrical network having an input 1 and an output 2. Connected serially between the input and output, there is a gain reducer 3 and an amplifier l. Likewise associated with the input and output, there are two shunt paths for repeating audio frequency current varia tions. One shunt path is formed by the unilateral repeating device 5, bass pass 6, and control means 7, while the other path is formed by unilateral repeating device 8, treble pass 9, and control means 10. These shunt paths are connected to the input 1 thru a common phase changer 11, and are connected to the output 2 thru the amplifier 4. As will be presently explained, amplifier 4 is preferably of the thermionic or electron relay type, and preferably the unilateral 'repeating devices 5 and 8 are also formed by electron relays or equivalent means having amplifying characteristics.

It may be briefly pointed out with respect to Fig. 2 that the bass and treble gains thru the two shunt paths can be adjusted or varied by the devices 7 and 10, and the combined effect of these two shunt paths having their respective gains produce what can be termed a compensating gain for the network. The gain occurring thru reducer 3 and amplifier 4: to the exclusion of the shunt paths can be termed the normal gain and can be adjusted to be substantially zero, or at least substantially less than the respective gains thru the two shunt paths. Phase changer 11, as will be later explained, serves to efiect a proper phase change whereby the current variations repeated by the two shunt paths are in proper phase with respect to the current repeated thru reducer 3.

Referring now to the detailed circuit diagram of Fig. 1, the input circuit 1 is formed by conductors 21 and 22, While the output 2 is formed byconductors 23 and 24. The gain reducer which is connected tothe input 1 is formed in this instance by resistances 26 and 27, resistance 26 being connected across conductors 21 and 22. Conductor 28 is connected to one terminal of resistance 27 thru condenser 33 and an adjustable tap connection 29 interconnects resistances 26 and 27. The amplifier designated generally at 4 in Fig. 2 is formed by an electron relay 31, which can be of the usual three element type, being provided with a grid or control element, a filament or cathode, and a plate or anode. The grid or control element of electron relay 31 is connected to conductor 28 while the plate or anode is connected to output conductor 23. Conductors 22 and 24 of the input and output respectively are shown connected by the grounded conductor 32, thru condensers 34 and 36 respectively, to which the cathode of electron relay 31 is also connected. Assuming that the cathode of electron relay 31 is a filament or utilizes a filament as a source of heat, this filament can be energized from a common A-battery circuit such as will be presently explained. In order to properly segregate the grid circuit of electron relays 31 and 54 from B-battery potentials which may be applied to conductors 21 and 22, blocking condensers 33, 34 and 68 capable of passing both bass and treble frequencies are inserted in series with conductors 28, 32 and 20, respectively. Likewise a similar blocking condenser 36 is inserted between the point of connection with the cathode of relay 31, and the output conductor 24.

It is desirable to so adjust resistors 26 and 27 that the loss or negative gain effected in the transfer of current variations from the input 1 to the grid circuit of electron relay 31, is substantially equal to the positive gain effected by repeating the current variations thru electron relay 31. Therefore, considering that part of the network which has been described above with reference to Fig. 1, apart from the remainder of the circuits, the net gain, which is herein referred to as the normal gain, is substantially zero.

That part of the network which forms a path for repeated current variations for effecting a bass gain, includes an electron relay 41, or equivalent unilateral repeating device having amplifying characteristics. A grid leak resistor 42, which is preferably adjustable or variable, is connected across the grid and cathode of the same. Connected in series relationship between the plate or anode of relay 41 and conductor 28, there is a condenser 43 capable of passing the lower voice frequencies,and also a circuit 44 which preferably has both capacitative and resistance components. As an example of a suitable circuit 44, I have shown one side of condenser 47 connected to resistor 46 and condenser 43 thru resistance 51. The other side of condenser 47 connects to the grounded filament circuit thru conductor 50. The resistor 51 can be of fixed value. To eifect an adjustment of capacitance condenser 47 can be shunted by another condenser 48, upon closing switch 49. Interposed in series between circuit 44 and conductor 28 there is a resistor 53 which is preferably adjustable or variable, and as will be presently explained, adjustments of this resistor serve to adjust the bass gain. The grid of electron relay 41 is connected to. the plate or anode of another electron relay 54, thru a series condenser 56. This condenser is of suiiicient capacitance to readily pass the lower or bass frequencies.

That portion of the network serving as a gain path for high or treble voice frequencies consists of an electron relay 57, having its grid connected to the grid of relay 41 thru a series condenser 58. Condenser 58 is of such capacitance that it will pass relatively high voice frequencies, or treble frequencies, but will offer relatively high impedance to bass frequencies. Connected be- F tween the plate or anode of relay 57 and conductor 28, there is a condenser 59 in series relationship with a relatively fixed resistor 61 and an adjustable or variable resistor 62. Condenser 59 is likewise of such capacitance that it will offer relatively high impedance to bass frequencies, but will pass treble frequencies. The capacitance afiorded at this point can be increased by an additional condenser 63, which can be connected in shunt with condenser 59 by closing switch 64. Relay 57 is also provided with a suitable grid leak resistor 66, which is connected across the grid and cathode.

Electron relay 54 serves to correct or change the phase angle of current variations applied from the input 1 to the grids of electron relays 41 and 57. The grid of electron relay 54 is connected to conductor 21 of the input 1 thru conductor 20 and series condenser 68 and is also connected to grid leak resist-or 69.

The relays 41 and 57 cause a phase change angle of 180 degrees and the relay 54 also changes the phase angle. Thus current variations of compensating gain will be in phase with current variations of normal gain impressed on grid of relay 31.

In order to supply suitable positive B- battery potential to the plates of electron relays 54, 41 and 57, a B-battery conductor 71 is connected to the plates of these relays thru resistors 72, 73 and 74. The filaments of the various electron relays are shown connected to the common A-battery circuit 76,

em-n29 one side of which is connected to conductor 32, while the other side is connected to A- battery terminal 77 thru switch 78. The negative A-battery terminal 79, which can also serve as a negative B-battery terminal, is connected to conductor 32. Positive B- battery terminal 81 is connected with conductors 24 and 71.

Operation of the network described with reference to Fig. 1 can be explained as follows: Input 1 is connected to some preceding part of an electrical system serving as a source of current variations of audio frequencies. Generally an electron relay ampli tier immediately precedes input 1 and has its plate circuit connected to conductors 21 and 22. Output 2 is connected to further electrical apparatus which generally serves to translate the current variations into sound. Usually such further apparatus includes an electron relay amplifier having its input coupled to output 2. Current variations impressed upon the input 1 are repeated thru the reducer afforded by resistors 26 and 2?", and are repeated by relay 31 to the output 2. As has been previously explained, the gain for this path thru the network, preferably relatively low, as for example substantially zero, and is termed the normal gain. Current variations of all audio frequencies are also impressed upon the grid of electron relay 54, the plate of which is coupled to the grids of electron relays 41 and 57, thru condensers 56 and 58. Both bass and treble frequencies are impressed upon the grid of relay 41, due to the relatively large capacitance of condenser 56, while mainly treble frequencies are impressed upon the grid of relay 57 due to the relat vely small capacitance of condenser 58. Circuit 44 connected between the plate of relay 41 and the grid of relay 31 discriminates against relatively high or treble frequencies and in favor of the lower or bass frequencies. This effect is made possible because of the resistance and capacitaserves tonarrow the bass gainaor to cause absorption of a greater range of high frequencies, while opening switch 49 serves to widen the bass gain. By varying the value of resistor 53 the volume of the bass gain can be varied between practical limits. The effect of varying this resistance will be evident when it is considered that it is connected in series with the connection from the plate of relay 41 to the grid of relay 31. Therefore a decrease in impedance accompanying a decrease in the res stance of resistor 53 causes an increase in the volume of bass gain, while increase in the value of resistor 53 increases the impedance of the connection between the plate of relay 41 to the grid of re lay 31 thus decreasing the volume of bass gain.

As has been previously mentioned, condenser 58 is of such capacitance that it ofiers relatively high impedance to bass frequencies. Therefore principally treble frequencies are applied to the grid of relay 57. A further discrimination in favor of treble frequencies is effected by condenser 59, which is also of relatively low capacitance. By closing switch 64 and connecting the shunt of condenser 63 with condenser 59, the range of the treble gain effected by relay 5? can be widened. Adjustments or variations of resistor 62 likewise serve to vary the volume of treble gain, operating in substantially the same manner as resistor 53 for relay 41. Fixed resistors 46 and 61 in conjunction wth the adjustable or variable resistors 53 and 62, serve the useful function of making the volume control effected by variations of resistors 53 and 62, more gradually. They also tend to prevent excess gain of relays 41 and 57. Resistor 46 also tends to prevent circuit 44 from absorbing some of the higher audio frequencies repeated thru the normal gar'n, when variable resistance 53 is adjusted to a lower value to increase bass gain. To further avoid this effect the resistor 51 is connected in series between resistor 46 and condenser 47 and performs several useful results. For example, it permits relay 41 to amplify just enough of the higher audio frequencies to offset the frequenc es which are otherwise absorbed by circuit 44 as explained. It has also been found that the plate or anode of relay 41 tends to have a rectifying effect. thus absorbing part of the positive wave of the higher audio frequencies being repeated thru the normal gain when bass gain is cut in or increased. Since resistor 51 permts relay 4-1 to pass some of the higher frequencies together with the bass frequencies, such undesired rectification and absorption are avoided.

Resistor 52, which is preferably adjustable or variable, serves the useful function of reducing the normal gain when the bass gain is increased by decreasing the value of resistor 53. This result is made possible due to the fact that resistors 52 and 53 are in series between the grounded filament circuit of the network and the grid of relay 31. Without such an arrangement the overall. gain of the network would become too great when bass gain is cut in or increased, th s requiring other adjustments of the network.

Under certain operating conditions when bass gain is cut in or increased, there will be a tendency for the network to motor boat.

Such a tendency toward motor boating can be eliminated by decreasing the value of resistor 42.

lVhen the network is installed with any particular amplifying system, it is evident that certain adjustments must be made, as for example adjustments of resistors 42 and 52, in order to insure stability, and in order to make possible a proper control of the bass and treble gains by varying resistors 53 and 62. After such adjustments are made for a given set of operating conditions, resistors 42 and 52 can remain fixed, irrespective of variations in the values of resistors 53 and 62. Likewise resistors 26 and 27 can remain fixed after proper adjustments are made.

Assuming now that the network is utilized in conjunction with an audio frequency amplifying system having a drooping characteristic curve for the lower or base frequencies, the overall characteristic can be corrected by increasing the bass gain to a proper value, that is by decreasing the value of resistor 53. Likewise, if the amplifying system has a drooping characteristic for the higher frequencies, the overall characteristics of the system, that is the system together with the network, can be corrected by cutting in the treble gain. here the audio frequency current "ariations applied to the amplifying system originate in a sound record, as for example a phonographic or film record, adjustment can be made in the network to compensate for defective recording of either high or low frequencies, or both. Likewise compensating ad ustments of the network can be made to offset characteristics of a loud speaker of poor fidelity supplied 7 sound waves.

It is evident that my network can be employed in conjunction with audio frequency amplifying systems having various types of conventional couplings. For example, in

- Fi g. 3, my network, which is designated generally at 86, is shown connected between the stages of an audio frequency amplifier system having transformer coupling. The input to the system is indicated at 87, and is coupled by transformer 88 to the electron relay amplifier 89. The output of amplifier 89 is connected to the input 1 of network 80. The output 2 of network 86 is coupled thru transformer 91, to the input of the electron T relay amplifier 92. The output of amplifier 92 supplies the loud speaker or equivalent translator 93.

Fig. 4 illustrates my network applied to a resistance coupled audio frequency amplifying system. In this case the audio frequency current variations are applied to the input 90 of the system, and are amplified by the electron relay 9?. The output of relay 9'7 connected to the input 1 of network So. The output 2 of network 86 has a resistance coupling with the grid circuit of electron relay amplifier 93. The output of amplifier 98 is further amplified by electron relay 09, and is'then applied to the loud speaker or trans lator 92.

The proper values for the various resistors and condensers utilized in my network can be readily determined by one skilled in the art for a network intended to operate for a certain latitude of conditions. For example in one network which I have constructed, resistors 26 and 27 have a total value of 25,000 ohms. Grid leak resistor 37 for relay 31 has a value of 100,000 ohms. Grid leak resistors 42, 00 and 69 have values of 12,000, 30,000 and 100,000 ohms respectively. Plate circuit resisters '42, 73 and Ti have values of 75,000 ohms, 15,000 ohms and 30,000 ohms respectivcly. Resistors 46 and 51 have values of 15,000 and 1,000 ohms respectively. Resistor 52 has a value of 12,000 olnns and resistor 01 for relay 57 has a value of 25,000 ohms. Variable resistors 53 and 62 have a maximum resistance of substantially 2 megohms and a minimum resistance of substantially 10,000 ohms. Condensers 33, 3a, 36, 68, 56, i3, each have a capacitance of 1 microfarad. Condensers 47, and 48 are of .0 1 and .1 microfarad, capacitance respectively. Condensers 58, 59 and 63 are of .006, .001 and .0025 m. f. respectively.

I have previously referred particularly to the use of my network in conjunction with radio broadcast receivers, electrical phonographs, and talking moving picture apparatus. Other uses which can be mentioned are for repeater stations of transcontinental wire hookups such as are employed in connection with raoio broadcasting stations, electrical transcription broadcasting or recording, and public address systems.

Havin thus described this invention, what l claim and desire to secure by Letters Patent 1s:

1. In an electrical network adapted to repeat current variations of voice frequencies, electrically coupled input and output circuits for transmitting the entire voice range, additional circuits coupled to said input and output circuits and including electron relay amplifiers, said additional circuits being characterized in that they form separate paths for treble and bass frequencies, and means for separately controlling the respective amplification gains of said additional circuits.

2. In an electrical network adapted to repeat current variations of voice frequencies, said network having input and output circuits for transmitting the entire voice range, a plurality of additional circuits shunted between said input and outputcircuits, electron relay amplifying means in said additional circuits, means interposed in one of said circuits serving to cause the same to offer less impedance to the passage of treble frequencies than to the passage of bass frequencies, means interposed in another of said additional circuits serving to cause the same to pass bass frequencies in favor of treble frequencies, and means for separately controlling the gain in said additional circuits.

3. In an electrical network adapted to repeat current variations of voice frequencies, said network having input and output circuits for transmitting the entire voice range, a plurality of additional circuits shunted between said input and output circuits, electron relay amplifying means in said additional circuits, means interposed in one of said circuits serving to cause the same to offer less impedance to the passage of treble frequen cies than to the passage of bass frequencies, means interposed in another of said additional circuits serving to cause the same to pass bass frequencies in favor of treble frequencies, each of said interposed means consisting of resistance and capacitative components only, and means for separately controlling the gain in said additional circuits.

4. In an electrical network adapted to repeat current variations of Voice frequencies, said network having input and output circuits, means forming two shunt paths for re peating current variations between the input and output circuits, one of said paths including in series relationship, an electron relay amplifier, capacitance capable of passing bass frequencies, capacitance shunted byresistance, and a variable resistor, the other of said paths including in series relationship another electron relay amplifier, capacitance serving to pass principally treble frequencies, and a variable series resistor.

5. In an electrical network adapted to re peat current variations of voice frequencies, said network having input and output circuits, an electron relay amplifier and a gain reducer interposed between said circuits, and means forming two shunt paths for repeating current variations between the input and output circuits, one of said shunt paths having a gain for bass frequencies which is greater than the normal gain thru the reducer and said electron relay amplifier, the other of said paths having a gain for treble frequencies which is greater than the normal gain thru the reducer and said electron relay amplifier.

6. In an electrical network adapted to repeat current variations of voice frequencies,

said network having input and output circuits, an electron relay amplifier and a gain reducer interposed between said circuits, means forming two shunt paths for repeating current variations between the input and output circuits, one of said shunt paths having a gain for bass frequencies which is greater than the normal gain thru the reducer and said electron relay amplifier, the other of said paths having a gain for treble frequencies which is greater than the normal gain thru the reducer and said electron relay amplifier, and phase correcting means for both said paths.

7. In an electrical network adapted to repeat current variations of voice frequencies, said network having input and output circuits, an electron relay amplifier and a gain reducer interposed between said circuits, phase changing means connected to the input circuit, means forming two shunt paths connected between said phase changing means and the output circuit for repeating current variations, one of said shunt paths including in series relationship an electron relay amplifier, capacitance capable of passing bass frequencies, capacitance shunted by resistance, and a variable resistor, and the other of said paths including in series relationship a third electron relay amplifier, capacitance serving to pass principally treble frequencies, and a variable series resistor.

8. A method of utilizing an electrical network for repeating voice frequencies, the network being characterized by three shunt paths between its input and output circuits for repeating current variations, said method comprising effecting a relatively low normal gain thru one of said paths for frequencies over the entire voice range, and effecting dif ferent gains thru the other of said paths for bass and treble frequencies.

9. A method of utilizing an electrical network for repeating voice frequencies, the network being characterized by three shunt paths between its input and output circuits for repeating current variations, said method comprising effecting a relatively low normal gain thru one of said paths for frequencies over the entire voice range, causing the other two paths to discriminate respectively as to treble and bass frequencies, and varying the impedances of said other two paths to adjust their respective gains.

In testimony whereof I have hereunto set my hand this 15th day of October, 1930.

MAXIMO AGUIRRE.

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