U.S. patent number RE37,130 [Application Number 09/192,160] was granted by the patent office on 2001-04-10 for signal conditioning apparatus.
Invention is credited to David Fiori, Jr..
United States Patent |
RE37,130 |
Fiori, Jr. |
April 10, 2001 |
Signal conditioning apparatus
Abstract
A signal conditioning system that receives inputs from at least
one pair of conductors connected to its input. Each such input is
processed by an input filter and presented to a buffer amplifier.
Each such input filter and buffer amplifier refers to and is
powered by independent power sources whose power return reference
potentials are independently determined by the potential of the
corresponding input signal potential reference conductor for the
signal frequencies of interest. The outputs of all such buffer
amplifiers, the power return reference potentials, and the power
return reference potential of the conditioning circuit output are
all appropriately added or subtracted in the next circuit stage.
This circuit stage consists of an amplifier buffer having low
output impedance which is powered by another independent power
source whose power return reference potential is independently
determined by the potential of the output signal reference
conductor. The output of this circuit stage is connected to an
output inductor circuit which in turn drives the output signal
conductor. The output includes a filter, and is designed to
decouple unstable loading conditions while rejecting external
influences on the output signal. The invention also includes means
that connect the reference potential of the destination of the
output conductors to the system power ground potential. The present
invention provides a relatively inexpensive and efficient way of
reducing or eliminating interference caused by coax cabling in
audio, power and video amplifiers, for example.
Inventors: |
Fiori, Jr.; David (Yardley,
PA) |
Family
ID: |
46256164 |
Appl.
No.: |
09/192,160 |
Filed: |
November 13, 1998 |
PCT
Filed: |
April 28, 1995 |
PCT No.: |
PCT/US95/05293 |
371
Date: |
June 07, 1995 |
102(e)
Date: |
June 07, 1995 |
PCT
Pub. No.: |
WO95/30273 |
PCT
Pub. Date: |
November 09, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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234343 |
Apr 28, 1994 |
5436593 |
|
|
|
879941 |
May 8, 1992 |
5386148 |
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Reissue of: |
448383 |
Apr 28, 1995 |
05694081 |
Dec 2, 1997 |
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Current U.S.
Class: |
330/69;
330/126 |
Current CPC
Class: |
H03F
3/195 (20130101); H03F 3/68 (20130101); H04B
3/28 (20130101) |
Current International
Class: |
H03F
3/68 (20060101); H03F 3/189 (20060101); H03F
3/195 (20060101); H04B 3/02 (20060101); H04B
3/28 (20060101); H03F 003/45 () |
Field of
Search: |
;330/69,107,124R,126
;381/99,100,120,121 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Morrison, Ralph, "Grounding and Shielding Techniques" 3rd ed. pp.
69-71, 1986.* .
International Search Report PCT/US95/05293 Apr. 28, 1995 7 pg.
.
Punch 150 Schematic N Rockford Corp, Tempe, AZ Author Unknown Dec.
20, 1983 1 pg. .
"Probe Aufs Exempel" Schorer, Edwin Jan. 1985 Funkschau, vol. 57,
No. 23, pp. 80-84..
|
Primary Examiner: Mottola; Steven J.
Attorney, Agent or Firm: Caesar, Rivise, Bernstein, Cohen
& Pokotilow, Ltd.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a 371 of PCT/US95/05293 filed Apr. 28, 1995 and
a continuation-in-part of application Ser. No. 08/234,343 filed
Apr. 28, 1994, now U.S. Pat. No. 5,436,593, which is a
continuation-in-part of application Ser. No. 07/879,941, filed May
8, 1992, now U.S. Pat. No. 5,386,148.
Claims
What is claimed is:
1. An amplifier circuit comprising:
a first stage for amplifying at least one applied signal and for
generating at least one intermediate signal proportional to a
potential difference between the at least one applied signal and at
least one return reference signal corresponding to the at least one
applied signal;
a second stage, operatively coupled to the first stage, for
frequency filtering the intermediate signal, the second stage
generating at least one filtered intermediate signal and an
inverted filtered intermediate signal which is proportional to a
potential difference between the filtered intermediate signal and
the at least one return reference signal corresponding to the at
least one applied signal; and
a third stage for generating an output signal which is a sum of the
filtered intermediate signal generated in the second stage minus a
potential of the inverted filtered intermediate signal generated in
the second stage.
2. An amplifier circuit as recited in claim 1, wherein the first
stage comprises a non-inverting amplifier.
3. An amplifier circuit as recited in claim 1, wherein the second
stage comprises a highpass filter.
4. An amplifier circuit as recited in claim 1, wherein the second
stage comprises a lowpass filter.
5. An amplifier circuit as recited in claim 1, wherein the second
stage comprises an inverting opamp circuit for generating the
inverted filtered intermediate signal.
6. An amplifier circuit as recited in claim 1, wherein the second
stage comprises a lowpass filter for providing a low frequency
output and a highpass filter for providing a high frequency output
and means for selectively switching therebetween.
7. An amplifier circuit as recited in claim 1, further comprising a
constant current source for driving the first and second stage with
a constant current.
8. An amplifier circuit as recited in claim 1, further comprising
power amplification circuitry for providing current amplification
of the output signal from the third stage.
9. An amplifier circuit as recited in claim 1, wherein the at least
one applied signal is input from a source by a coaxial cable.
10. An amplifier circuit as recited in claim 1, the first stage
comprising an operational amplifier circuit.
11. An amplifier circuit as recited in claim 10, wherein the first
stage comprises a non-inverting amplifier.
12. An amplifier circuit as recited in claim 1, the third stage
comprising an operational amplifier circuit.
13. An amplifier circuit as recited in claim 1, wherein the second
stage comprises a cross-over circuit.
14. A system for amplifying and conditioning signals, the system
comprising:
a first circuit comprising:
a) an input for receiving at least one input signal;
b) a first stage for generating at least one intermediate signal
which is proportional to a potential difference between the at
least one input signal and at least one return reference signal
corresponding to the at least one input signal, said first stage
further generating at least one inverted signal corresponding to
the at least one input signal; and
c) a second stage, operatively coupled to the first stage, for
generating an output signal which is a sum of the at least one
intermediate signal generated in the first stage plus an output
return reference minus a potential of the inverted signal; and
a second circuit comprising an amplifier for current amplifying the
output signal from the second stage of the first circuit.
15. A system for amplifying and conditioning signals as recited in
claim 14, wherein the first circuit and the second circuit are
provided in separate and distinct housings.
16. A system for amplifying and conditioning signals as recited in
claim 15, wherein the second circuit includes a power supply and
supplies power to the first circuit.
17. A system for amplifying and conditioning signals as recited in
claim 14, the first stage further comprising frequency filter
circuitry for frequency filtering the at least one input
signal.
18. A system for amplifying and conditioning signals as recited in
claim 17, wherein the frequency filter circuitry comprises a low
pass filter.
19. A system for amplifying and conditioning signals as recited in
claim 17, wherein the frequency filter circuitry comprises a high
pass filter.
20. A system for amplifying and conditioning signals as recited in
claim 17, wherein the frequency filter circuitry comprises a low
pass filter and a high pass filter and means for selectively
switching therebetween.
21. A system for amplifying and conditioning signals as recited in
claim 14, wherein the amplifier comprises a power amplifier.
22. A system for amplifying and conditioning signals as recited in
claim 14, wherein the first circuit comprises a preamplifier.
23. A system for amplifying and conditioning signals as recited in
claim 14, wherein the amplifier circuit comprises an amplifier for
amplifying video signals.
24. A system for amplifying and conditioning signals as recited in
claim 14, wherein the first circuit and second circuit are provided
in the same housing.
25. A system for amplifying and conditioning signals as recited in
claim 14, further comprising circuitry for equalizing, noise
reducing and effects processing the signal output from the second
stage and for providing the output signal to the second
circuit.
26. A circuit for amplifying and conditioning audio signals in an
audio system, the circuit comprising:
a) a first stage for generating at least one intermediate audio
signal which is proportional to a potential difference between at
least one applied audio signal and at least one return reference
signal corresponding to the at least one audio signal, said first
stage further generating at least one inverted applied audio signal
corresponding to the at least one applied audio signal;
b) a second stage, operatively coupled to the first stage, for
generating an output audio signal which is a sum of the at least
one intermediate audio signal generated in the first stage plus an
output return reference signal minus a potential of the inverted
applied audio signal; and
c) a power amplifier for current amplifying the output audio signal
generated in the second stage.
27. A circuit for conditioning video signals in a video system, the
circuit comprising:
a) a first stage for generating at least one intermediate video
signal which is proportional to a potential difference between at
least one applied video signal and at least one return reference
signal corresponding to the at least one applied video signal; said
first stage further generating at least one inverted applied video
signal corresponding to the at least one applied video signal;
and
b) a second stage, operatively coupled to the first stage, for
generating an output video signal which is a sum of said at least
one intermediate video signal generated in the first stage plus an
output return reference signal minus a potential of the inverted
applied video signal.
28. A circuit for conditioning signals in a system, comprising:
a first stage having a buffer amplifier for receiving at least one
input signal and generating therefrom at least one intermediate
signal which is proportional to a potential difference between the
at least one input signal and at least one return reference signal
corresponding to the at least one input signal;
a power supply circuit coupled to said first stage for providing a
constant current with a high impedance to increase electrical
isolation between the first stage and the at least one return
reference signal; and
a second stage, operatively coupled to the first stage, for
generating an output signal which is a sum of the at least one
intermediate signal generated in the first stage minus a potential
of the at least one return reference signal plus an output return
reference signal.
29. The circuit according to claim 28, further comprising power
supply circuitry coupled to said second stage for providing a
constant current with a high impedance to increase electrical
isolation between the second stage and the output return reference
signal.
30. The circuit according to claim 29, wherein a power return
reference potential of said power supply circuit coupled to said
first stage is independently determined by a potential of said
return reference signal corresponding to said input signal.
31. The circuit according to claim 30, wherein a power return
potential of said power supply circuitry coupled to said second
stage is independently determined by a potential of said output
return reference signal.
32. Apparatus for conditioning signals, comprising:
a) a first circuit part having a first buffer amplifier for
receiving a first applied signal and generating therefrom a first
intermediate signal proportional to a potential difference between
said first applied signal and a first return reference signal
corresponding to said first applied signal, and having a first
power supply circuit for providing a constant current to said first
buffer amplifier with a high impedance, said first power supply
circuit having a first power return reference potential
independently determined by a potential of said first return
reference signal;
b) a second circuit part having a second buffer amplifier for
receiving a second applied signal and generating therefrom a second
intermediate signal proportional to a potential difference between
said second applied signal and a second return reference signal
corresponding to said second applied signal, and having a second
power supply circuit for providing a constant current to said
second buffer amplifier with a high impedance, said second power
supply circuit having a second power return reference potential
independently determined by a potential of said second return
reference signal;
c) a third circuit part, operatively coupled to said first circuit
part, for generating a first output signal which is a sum of said
first intermediate signal plus an output return reference signal
minus a potential of said first return reference signal;
d) a fourth circuit part, operatively coupled to said first circuit
part, for generating a second output signal which is a sum of a
potential of said second return reference potential plus said
output return reference signal minus said second intermediate
signal; and
e) an output circuit for bridging said first and second output
signals.
33. The apparatus according to claim 32, wherein said first and
second circuit parts further comprise first and second inverters,
respectively, for providing respective first and second inverted
signals corresponding to said first and second applied signals,
respectively, said first and second inverted signals being applied
to the third and fourth circuit parts, respectively, to
substantially double voltages in the output signals thereof.
34. The apparatus according to claim 32, further comprising a first
filter circuit coupled between said first buffer amplifier and said
third circuit part, for filtering said first intermediate signal,
and a second filter circuit coupled between said second buffer
amplifier and said fourth circuit part, for filtering said second
intermediate signal.
35. The apparatus according to claim 34 wherein said first and
second filter circuits include respective first and second
operational amplifiers driven by respective first and second
constant current sources each having a high impedance..Iadd.
36. A circuit for conditioning signals in a system having a power
supply and a power supply reference potential, said circuit
comprising:
a first stage having an amplifier circuit for receiving, from an
input source, an input signal and an input source reference
potential different from the power supply reference potential, said
first stage generating an intermediate signal which represents the
sum of the input source reference potential and a proportion of the
input signal;
a first power supply circuit coupled to said first stage, said
first power supply circuit isolating the power supply from said
first stage by drawing a constant current from the power supply
with respect to changes in the input source reference potential;
and
a second stage coupled to said first stage, and responsive to said
intermediate signal, for generating an output signal which is
proportional to the input signal. .Iaddend..Iadd.
37. A circuit for conditioning signals in a system as defined by
claim 36, further comprising a second power supply circuit coupled
to said second stage having an output and an output device coupled
to the output of said second stage and having an output device
reference potential different from the input source reference
potential, said power supply circuit isolating the power supply
from said second stage by drawing a constant current from the power
supply with respect to changes in the output device reference
potential. .Iaddend..Iadd.
38. A circuit for conditioning signals in a system, comprising:
a first stage having an amplifier circuit for receiving, from an
input source, an input signal and an input source reference
potential and generating an intermediate signal which represents
the sum of the input source reference potential and a proportion of
the input signal;
a first power supply circuit coupled to said first stage, said
first power supply circuit comprising voltage regulation means for
drawing a constant current from the power supply with respect to
changes in the input source reference potential to isolate the
power supply from said first stage; and
a second stage coupled to said first stage, and responsive to said
intermediate signal, for generating an output signal which is
proportional to the input signal. .Iaddend..Iadd.
39. A circuit for conditioning signals in a system as defined by
claim 38, further comprising a second power supply circuit coupled
to said second stage having an output and an output device coupled
to the output of said second stage and having an output device
reference potential different from the input source reference
potential, said second power supply circuit isolating the power
supply from said second stage by drawing a constant current from
the power supply with respect to changes in the output device
reference potential. .Iaddend..Iadd.
40. A signal conditioning circuit in a system having at least one
input source, a power supply and an output device, said signal
conditioning circuit being interposed between the at least one
input source and the output device and being coupled to the power
supply, the at least one input source having a first reference
potential, the output device and the power supply having a second
reference potential different from the first reference potential,
said signal conditioning circuit comprising:
a first stage coupled to a second stage;
a power supply circuit coupled to the power supply and to said
first stage for isolating the power supply from said first stage by
drawing a constant current from the power supply with respect to
changes in the first reference potential;
said first stage having an amplifier circuit for receiving an input
signal and the first reference potential from the at least one
input source and generating an intermediate signal that represents
the sum of the first reference potential and a proportion of the
input signal; and
said second stage responsive to said intermediate signal for
generating an output signal which is proportional to the input
signal. .Iaddend..Iadd.
41. A signal conditioning circuit in a system having at least one
input source, a power supply and an output device, said signal
conditioning circuit being interposed between the at least one
input source and the output device and being coupled to the power
supply, the at least one input source having a first reference
potential, the output device having a second reference potential
different from the first reference potential and the power supply
having a third reference potential different from the first and
second reference potential, said signal conditioning circuit
comprising:
a first stage coupled to a second stage;
a first power supply circuit coupled to the power supply and to
said first stage for isolating the power supply from said first
stage by drawing a constant current from the power supply with
respect to changes in the first reference potential;
a second power supply circuit coupled to the power supply and to
said second stage for isolating the power supply from said second
stage by drawing a constant current from the power supply with
respect to changes in the second reference potential;
said first stage having an amplifier circuit for receiving an input
signal and the first reference potential from the at least one
input source and generating an intermediate signal that represents
the sum of the first reference potential and a proportion of the
input signal; and
said second stage responsive to said intermediate signal for
generating an output signal which is proportional to the input
signal. .Iaddend..Iadd.
42. The signal conditioning circuit of claim 41 wherein said first
stage generates a second intermediate signal that represents the
difference of the first reference potential and a proportion of the
input signal, said second stage responsive to said second
intermediate signal for generating said output signal from said
intermediate signal and said second intermediate signal.
.Iaddend..Iadd.
43. A signal conditioning circuit in a system having at least one
input source, a power supply and an output device, said signal
conditioning circuit being interposed between the at least one
input source and the output device and being coupled to the power
supply, the at least one input source and the power supply having a
first reference potential and the output device having a second
reference potential different from the first reference potential,
said signal conditioning circuit comprising:
a first stage coupled to a second stage;
a power supply circuit coupled to the power supply and to said
second stage for isolating the power supply from said second stage
by drawing a constant current from the power supply with respect to
changes in the second reference potential;
said first stage having an amplifier circuit for receiving an input
signal and the first reference potential from the at least one
input source and generating an intermediate signal that represents
the sum of the first reference potential and a proportion of the
input signal; and
said second stage responsive to said intermediate signal for
generating an output signal which is proportional to the input
signal. .Iaddend..Iadd.
44. A signal conditioning circuit in a system having at least one
input source, a power supply and an output device, said signal
conditioning circuit being interposed between the at least one
input source and the output device and being coupled to the power
supply, the at least one input source and the output device having
a first reference potential and the power supply having a second
reference potential different from the first reference potential,
said signal conditioning circuit comprising:
an amplifier stage having an amplifier circuit for receiving an
input signal and the first reference potential from the at least
one input source and generating an intermediate signal that
represents the sum of the first reference potential and a
proportion of the input signal; and
a power supply circuit coupled to the power supply and to said
amplifier stage for isolating the power supply from said amplifier
stage by drawing a constant current from the power supply with
respect to changes in the first reference potential. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to circuits that use signal
conditioning circuitry to eliminate interferences caused by
magnetic fields, electric fields, and electro-magnetic or radio
frequency fields on conductors that provide electrical connection
between devices in a system. The present invention also relates to
various electronic circuit that drive conductors, the electronic
circuits including signal conditioning circuit to overcome the
adverse effects of their loading on the signal source. More
specifically, the present invention relates to audio amplifiers,
power amplifiers, video amplifiers, etc. that use signal
conditioning circuitry for achieving the above-noted benefit.
2. Description of Related Art
Conductors that provide electrical connection between devices in a
system are often the source of many types of electrical
interference. Magnetic fields, electric fields and electro-magnetic
or radio frequency fields are known to interfere with the fidelity
of signals conveyed over conductors which are subjected to those
fields. Furthermore, the ground or reference conductor of a typical
signal carrying pair of conductors are often connected to different
local ground potentials between one end of the conductor as
compared to the other, and currents are known to flow in such
conductors which then produce voltage drops on that conductor which
also interfere with the fidelity of the signals being conveyed. In
addition, these conductors, especially when very long, present
loads to the signal source that may adversely effect the fidelity
of the signal.
The problems of conveying signals over conductor pairs in various
types of electronic circuits including amplifier systems such as
audio amplifier systems, power amplifier systems, video amplifier
systems, etc. is well known. The conveyance of signals, especially
between powered devices, is often plagued by electro-magnetic
interference.
One method employed to reduce these interferences modulates the
signal so that it can be easily separated from the interference,
and then demodulates the signal at the destination. For example, an
analog-to-digital converter can be utilized to convey digital
impulses over the connecting conductors instead of analog voltage
potentials. The destination device in such instances must then
convert the signal back to an analog signal potential. Such
approaches, while effective, can be very costly, and require
extensive circuitry at both the sending and receiving ends of the
conductors. Such methods are exemplified by U.S. Pat. No. 4,922,536
to Hogue.
Another common method to reduce these interferences is to convey
such signals in a differential manner. A common approach utilizes a
three conductor shielded cable where two of the conductors deliver
the signal and its arithmetic inverse, and a third conductor,
usually a shield, conveys the ground reference potential voltage.
The conditioning circuit, usually placed at the destination end of
the conductors, forms the difference between the potential of the
first signal carrying conductor and the second signal carrying
conductor. In theory, both conductors are subject to the same
interferences, and the subtraction of the signals as conveyed will
eliminate the common mode noises. This approach, while effective in
eliminating most interference is nevertheless expensive and
difficult to implement. To adapt this approach in the general case
of processing signals between subsystems requires active circuitry
at the sending end to form the inverse signal, and a separate
active circuit at the receiving end to subtract the signals.
Multiple conductors are also required to be contained within a
single shield, which is more costly than conductors having only one
conductor surrounded by a shield. Such methods do not, however,
address any interference or other affects of the cables that
connect the transmitter and receiver to source and destination
respectively. Such methods are exemplified by U.S. Pat. No.
4,979,218 to Strahm, and is described at pages 69-71 of "GROUNDING
AND SHIELDING TECHNIQUES IN INSTRUMENTATION", by Ralph Morrison,
3rd Edition, 1986, Wiley-Interscience.
One source of interference in the conveyance of these differential
signals between electronic subsystems is referred to as the ground
loop. Because it is common for there to be multiple electronic
paths between the reference potentials of each subsystem, and since
such paths commonly include sources of interference, these
alternative paths are often responsible for the interference
present in those systems. Such ground loops are generally overcome
by eliminating any electrical connection by conductors between the
subsystems. "GROUNDING AND SHIELDING TECHNIQUES IN INSTRUMENTATION"
by Morrison describes the elimination of the effects of the
electrical connections between subsystems that convey their signals
by differential means through the use of tandem differential
amplifiers powered by electrically isolated power supplies.
The first differential amplifier in the Morrison reference
calculates the difference between the signals being conveyed, and
the second differential amplifier adds the reference potential of
the destination to the result of the first differential amplifier.
The result is that the reference potentials of the source of the
differential signal may differ from the reference potential of the
destination without effecting the expression of the signal at the
destination. However, such an approach is not easily adapted to
electronic systems consisting of single ended two wire signal
conductors. Consequently, this approach suffers from the same
limitations as devices that convey signals by differential means.
For example, there are no means suggested in Morrison for the
elimination or suppression of the magnetic field interference that
may be picked up between the two conductors enclosed in the shield,
due to differences in the magnetic field voltages induced in those
conductors. Moreover, Morrison does not address the pickup of
electric field interference or any other cable affects due to the
output cable.
The circuits shown in the Morrison reference are also particularly
subject to the variation of op-amp characteristics. In particular
the output impedance of the opamps used to determine A1 will
negatively impact the interference rejection of any common mode
voltage differences between source and destination reference
potentials as that impedance relates to the difference resistors of
gain stage A2. As this circuit characteristic is extremely gain and
temperature dependent, such inaccuracies are not easily controlled
without increased expense in the design of the output stages of
those circuits or without compromises inherent in the utilization
of higher impedances than would be appropriate in achieving other
performance objectives such as thermal noise and bandwidth which
are adversely affected by higher resistor values in this case.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide various
types of electronic circuits including amplifier systems, such as
audio, power and video amplifier systems, with circuitry to
suppress or eliminate the expression of all types of interference
in the wiring conveying analog voltage potential signals from a
source to a destination. This is accomplished in the present
invention by the unique combination of novel interference rejection
circuits that address the sources of interference in these systems
in a less costly and more efficient manner than other
approaches.
It is another objective of the present invention to remove any
effect that the loading of such wiring or the effects of the
loading of the destination in these devices may have upon the
accuracy of the signal as conveyed by the source of the signal.
It is a further objective of the present invention to accomplish
the preceding objectives with a minimum number of precision
resistors producing greater effective rejection than the prior art
for a given cost.
An additional objective of the present invention is the reduction
in sensitivity of the circuit action to the characteristics of the
gain circuits and/or operational amplifier circuits employed by the
circuit to achieve the various aims herein described.
Another objective of the present invention is to provide an
economical means of adjusting gain in these systems without
affecting the resulting interference rejection in practical
applications.
Yet another objective of the present invention is to afford greater
rejection of electric field interference and any electric field
affects, such as dielectric absorption, due to output cable
physics.
A further objective of the present invention is to effect these
objectives without altering the accuracy or fidelity of the
signal(s) being conveyed between subsystems.
Another objective of the present invention is to provide a device
which accomplishes every objective of the present invention as
described forthwith by means of an independent circuit which can
easily be inserted into the existing wiring between popular
electronic devices such as the above-described amplifier systems,
for example, and which can accomplish every objective of the
present invention as described forthwith with a minimum amount of
time required to install the device in these systems.
It is a further objective of the present invention to provide all
of the functions associated with state of the art amplification
systems while achieving the above-noted benefits with a minimum
amount of additional circuitry and without adding any additional
active circuitry in the signal path.
A further objective of the present invention is to provide for the
conditioning of single ended or differential signals with the same
circuit organization and interconnecting wire cable(s).
A further objective of the present invention is to provide for the
conditioning of differential signals, or any number of signals,
where each signal is produced with reference to independent
potential references which make higher levels of interference
rejection possible.
It is also an objective of the present invention to accomplish
every objective of the invention as described forthwith while
utilizing signal wiring between devices which consists of two
conductors arranged concentrically. This type of cabling is known
as "COAX" which is a shortening of the term "CO-AXIAL", and which
refers to a cable whose circular conductors share the same major
axis.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the drawing:
.[.FIG. 1 is.]. .Iadd.FIGS. 1A and 1B together constitute
.Iaddend.a circuit diagram of a preferred embodiment of the signal
conditioning circuitry to be included in various types of
electronic circuits according to various embodiments of the present
invention;
.[.FIG. 2 is.]. .Iadd.FIGS. 2A and 2B together constitute
.Iaddend.a circuit diagram of a typical audio amplifier;
.[.FIG. 3 is.]. .Iadd.FIGS. 3A and 3B together constitute
.Iaddend.a circuit diagram of the typical audio amplifier including
signal conditioning circuitry according to an embodiment of the
present invention;
FIG. 4 is a block diagram of an amplifier system according to an
embodiment of the present invention; and
FIG. 5 is a block diagram of another embodiment of the amplifier
system according to an embodiment of the present invention;
FIG. 6 is a block diagram of a video circuit including signal
conditioning circuitry according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, in which like reference numerals
identify identical or similar elements, and in particular to
.[.FIG. 1.]. .Iadd.FIGS. 1A and 1B.Iaddend., signal source 1 may be
understood to be differentially related to signal source 26 in
instances where signal 1 and signal 26 are both available and known
to relate to each other in an arithmetically inverse manner. Such a
relationship is not necessary to carry out the present invention.
Other relationships may be appropriate; indeed, if the circuit were
to be used as a mixer of signals, there may be no relationship at
all. Also, signal 1 or signal 26 need not convey a signal at all,
and either may be disconnected to apply the device to single ended
signals utilizing only two conductors to convey a signal, without
limiting the effectiveness of the device.
Signal 1 and Signal 26 are conveyed over coaxial cable(s) 4 and 29
respectively. Coaxial cables are preferred in connection with this
invention because the coaxial nature of the cables offers the
special benefit that both conductors respond nearly identically to
magnetic field interference by virtue of the high degree of axial
symmetry possible around the major axis of the cable run. By virtue
of this symmetry, the outer conductor will respond to magnetic
fields in substantially the same way as the inner conductor will in
accordance with Lenz's law which relates an induced voltage to the
rate of change of magnetic field strength. Hence magnetic field
disturbances in the vicinity of said cables will induce
substantially the same voltage in the outer conductor as such
interference will induce in the inner conductor.
The present invention is particularly effective at rejecting the
influence of any electric currents conducted by each shield that
would tend to shift the reference potential of each signal at its
source. This is often a problem because the ground potential
impedance of the source is less than ideal in practice. Since each
signal is generated with respect to its own reference potential
more exactly than with respect to any shared reference potential,
and since all such current will only substantially flow into that
source reference impedance, affecting both the signal source ground
potential and signal potential substantially equally, the present
invention will be very effective in eliminating interference so
induced. The extreme high impedances of the power supply circuit in
the preferred embodiment provides for this principle in a novel and
especially effective way at a much lower cost than other
techniques.
This power supply circuit is developed in the preferred embodiment
by very high impedance current source circuits composed of field
effect transistors 47, 22, 50 and 24 in combination with current
programming resistors 46, 21, 51 and 25 and opamps 48, 23, 52 and
26. The opamps provide the biasing necessary for the transistors to
conduct exactly that current required to produce that voltage
across the resistors that match the biasing voltages produced by
zener diodes 80 and 85 in combination with resistors 82 and 84.
Capacitors 81 and 86 are included to further reject any
interference which may be present on the power supply as provided
by contacts 91, 89 and 90. In this way an exact current is
precisely metered through each transistor to operate opamps 13, 16,
38, and 41. Because this current is metered so precisely, any
changes in potential at the opamp supply pins will have no bearing
on the current delivered. As a result, the effective impedance of
the power supply will be extremely high. The quality of this high
impedance current source is limited only by the gate-to-drain
capacitance of the field effect transistors used, which can be very
small depending on the device characteristics. Field effect
transistors with capacitances on the order of 0.05 pf are known to
exist in metal gate transistors designed for VHF mixers. Such
transistors would easily provide 3 megs of equivalent isolation at
1 Mega-Hz provided opamps 13, 16, 38 and 41 could handle that
frequency accurately.
Other transistors could be used as well. While field effect
transistors are preferred, ordinary PNP and NPN transistors have
proven to work satisfactorily, but available device characteristics
are not as ideal as field effect transistors for this purpose.
General purpose small signal transistors are limited in isolation
by the offset of the base current which varies with collector
voltage, and by larger base to collector capacitances, two effects
which compromise the performance of this circuit. Careful selection
of high B types or darlington configurations can go a long way
towards improving such circuits.
Each signal from source 1 or 26 is then subjected to resistor 5 and
30 respectively. This resistance is provided primarily as a path
for the input bias current necessary for the operation of
operational amplifiers 13 and 38. Such resistors are not, however,
required to carry out the present invention, yet are preferred to
enable the device to carry out the present invention in every
possible context. For example, a common context for the device
involves an input signal source that is blocked with a coupling
capacitor which would not permit the necessary bias current to flow
in the steady state without resistor 5 and 30. These resistors
should be designed with the highest resistance value practical
considering the effect of the resistor on the source electronics
and cable characteristics engendered in sources 1 and 26 and cable
4 and 29.
Capacitors 6, 9, 33 and 34 along with resistors 8 and 32 and
inductors 7 and 31 are all part of a Pi-filter arrangement designed
to reject frequencies far higher than the frequencies of interest
in the signal. Such a filter is preferred to prevent such high
frequency interference from interacting with various non-linear
elements in typical operational amplifiers, such as are indicated
as 13 and 16 in the drawings, and so prevent the demodulating or
converting of such high frequency interference to frequencies that
would otherwise interfere with the frequencies of interest.
Opamps 13 and 38 along with resistors 10, 11, 35 and 36 form buffer
amplifiers which may be designed to include gain according to the
ratio of the values of resistors 11 and 36 with respect to
resistors 10 and 35. Because the gain of these amplifiers may be
important in instances where differential signals are conditioned,
these gains should be well matched. However, in the case of a
single input, or multiple unrelated inputs, the precision of the
gain of this stage will not be important because each input and
each amplifier corresponding to each input refers to its own ground
reference potential separately. In order to refer to each ground
reference potential separately, such as local ground potentials as
indicated as 3 and 28, each such buffer opamp 13 and 38 must be
powered by separate and independent sources of power whose ground
return potentials can assume any value. Signal ground reference
potentials 3 and 28 may present by way of the ground conductors of
cable 4 and 29. In this way the opamp circuit can not inject any
currents into the signal carrying conductor, which would otherwise
be possible through various stray capacitances and internal opamp
circuits if the opamp's power supplies did not track the reference
ground potential of each input. Such injected currents could
produce severe feedback instabilities in addition to permitting the
expression of any noises that may be included with those injected
currents.
Each such opamp 13 and 38 provides, at its output, a signal
proportional to the signal provided at its input, but it provides
that signal potential with a much lower output impedance. Hence,
components may then be connected to the output of the opamps, such
as resistors 53 and 56, which inject interference currents into the
output of these amplifiers that are directly related to the
interference potential between the respective source signal grounds
3 and 28 and the output signal ground 79. The expression of these
currents is suppressed, to a large degree, by the ratio of output
impedance of the amplifier(s) 13 and 38 and the impedance of
resistors 53 and 56 respectively. In the preferred embodiment
configured for balanced signal sources as shown in .[.FIG. 1.].
.Iadd.FIGS. 1A and 1B.Iaddend., such interference due to said
opamps is additionally cancelled by the differential action of the
circuit comprising opamp 61, and resistors 53, 56, 59 and 57. In
this way rejection of the common mode interference is limited
primarily by the precision of the resistors 53 and 56 viz-a-viz
resistors 57 and 59. This result makes it possible to utilize
smaller values for these resistors and hence makes wider bandwidth
and lower noise levels possible.
Additional rejection of such opamp characteristics is offered by
the incorporation of opamps 16 and 41, which are especially
beneficial when the signal source is single ended and comprises
only signal 1. In this case, the circuit comprised of opamp 16,
resistor 14 and resistor 15 may be altered in design by connecting
resistor 39 to the positive input of opamp 38 instead of the
connection shown, and by matching the ratio of resistors 36 and 35
with the ratio of resistors 40 and 39 so connected. Such an
arrangement will produce the same common mode injected errors in
opamp 16 as are produced by opamp 13, and these errors will then be
subtracted by the differential action of the circuit of opamp 61 in
combination with resistors 53 and 55. This improvement could also
be applied to the balanced input source case by applying the
aforementioned modifications to the input circuit for the
complementary source.
Each signal presented at the output of opamps 13 and 38 is then
appropriately summed along with inverted signals produced by opamps
16 and 41. These signals and their individual complements hence
produce twice the voltage level possible between their outputs than
the single opamp 13 or 38 could provide. In addition, this
complementary output is presented symmetrically with reference to
the source ground potential as is related by the respective cable
shield 4 or 29, thus permitting the cancellation of the common mode
interference included in that reference potential as compared to
the destination reference potential. This arrangement makes it
possible to design the following differential gain stage with opamp
61 and resistors 53-57 and 59 with 1/2 the gain that would
otherwise be necessary, and this fact also reduces the sensitivity
of the resultant output to that common mode interference. When all
component sensitivities are taken into account, a worst case
improvement of 4 db in said common mode rejection ratio can be
expected without increasing the precision of the resistors required
by said differential gain stage.
In any event, the signal from opamps 13, 38, 41 and 16 are summed
by the following difference amplifier stage as follows: The signal
from opamp 13 is applied to opamp 61 by way of resistor 53 to
provide for the expression of that potential minus the inverted
version of that potential expressed with reference to the input
signal reference potential as presented by the shield conductor of
cable 4 by way of resistor 55. Likewise, resistor 54 provides for
the expression of its respective signal potential minus the
inverted version of that potential expressed about the input signal
reference potential ground 28 as presented by the shield conductor
of cable 29 by way of resistor 54. Furthermore, resistor 57
provides for the addition of the output reference ground 79 as
presented by the shield conductor of cable 75 to the signal output
of opamp 61. In this way the output potential of opamp 61 may
present a potential at its output that not only calculates the
differences between the input potentials and their ground reference
returns, but also adds in the output reference potential so that
the signal then tracks the reference potential used by the
destination receiving the output of opamp 61. These relationships
expressed mathematically are as follows:
Where
Vout=Output of opamp 61
Vog=Output ground reference potential as presented by the shield of
cable 75
Vin1+=Input from source 1 as presented by cable 4
Vin1g=Input ground reference potential from ground 3 as presented
by cable 4
G1=gain of opamp 13=(R10+R11)/R10
VG1+=Output of opamp 13=G1xVin1++Vin1g
VG1-=Output of opamp 16=-G1xVin1++Vin1g
Vin2+=Input from source 26 as presented by cable 29
Vin2g=Input ground reference potential from ground 28 as presented
by cable 29
G2=gain of opamp 38=(R35+R36)/R35
VG2+=Output of opamp 38=G2xVin2++Vin2g
VG2-=Output of opamp 41=-G2xVin2++Vin2g
G3=gain of differential amplifier stage with opamp 61=R.[.60.].
.Iadd.59.Iaddend./R55=R.[.60.].
.Iadd.59.Iaddend./R56=R57/R53=R57/R54
Vog=output ground potential as presented by the shield of cable
75
Vout=output of opamp 61=VG1+-VG1--VG2++VG2-+Vog.
Then the preferred embodiment of the present invention provides for
the following relationship:
Signal Output=Vout-Vog=G3x(2xG1xVin1+)-G3x
(2xG2xVin2+)=2xG3x((G1xVin+)-(G2xVin2+))
if G1=G2, which is normally the case:
Signal Output=2xG3xG1x(Vin1+-Vin2+)
In order to properly track the output reference potential, while
also driving the signal with respect to that reference potential,
it is also necessary to supply opamp 61 with power whose reference
return potential will accurately assume the same value as the
output reference ground 79 as presented by cable 75. This is done
in this embodiment by providing opamp 61 with its own separate and
independent source of power whose reference ground potential can
freely assume any value. Transistors 67 and 69 provide for such
power by implementing very high impedance current sources in the
same manner as described previously in connection with opamps 13
and 41.
The output of opamp 61 is also filtered, according to the present
invention to prevent the interaction of high frequencies picked up
in the output cable from being detected by the non-linearities of
the opamp at those high frequencies. Also, the inductor 72 and
resistor 73 serve to provide a finite, but higher impedance to the
opamp at higher frequencies than the capacitor 74 and the
capacitance of the cable 75 would present at high frequencies, and
which would otherwise render opamp 61 unstable in the servo action
of its gain controlling feedback. Also, inductor 72 provides for
very low impedance at lower frequencies so that the output cable 75
can be driven with extremely low impedance which can be very
effective in shunting any currents that may be injected by electric
fields along the cable, or by the electronic device to which the
cable may be connected. In addition, the low output impedance
afforded by inductor 72 makes it possible for opamp 61 to more
accurately drive any cable capacitance that may be presented by
cable 75. This is possible because a higher output impedance, as
would be necessary without inductor 72, could result in a low pass
RC filter (the R being resistor 73 and the C being the sum of
capacitor 74 and the effective capacitance of cable 75) that would
have a significant effect on the fidelity of the signal being
conveyed. In addition, such low drive impedance also shunts the
effects of the dielectric of the cable 75. This dielectric may not
be ideal as it may be subject to hysteresis-like effects such as
dielectric absorption. Low output impedance will effectively reject
such characteristics.
In addition, capacitors 58 and 60 may also be added to minimize the
tendency of some opamps to amplify higher frequencies in a manner
that is not consistent with feed back resistor values, and which
could compromise signal fidelity. Capacitor 60 shunts higher
frequencies that may be delivered by resistors 55 and 56 while
capacitor 58 increases the feedback applied to opamp 61 while it
shunts higher frequencies that may be delivered by resistors 53 and
54 to the output. To minimize the effects of these capacitors in
the frequency bands of interest, capacitors 58 and 60 should have
values that are inversely proportional to resistors 57 and 59
respectively.
One problem with a signal conditioning apparatus intended to
interface between two electronic subsystems is the range of
different types of inputs to which the device will be connected.
Destination devices can vary from having a ground connection that
is ultimately connected to the system ground potential to fully
isolated differential connections where there is equal, but finite,
and sometimes large impedances between the destination signal
ground connection and the system ground. Preferably, the present
invention is utilized in a system in which the destination signal
ground connection is connected to the system power return
potential. Since this is not always the case with all destination
devices, however, additional means to guarantee such a connection
may be included in the present invention.
There is often the occasion to provide signal conditioning for more
than one signal at a time. In such instances arrays of signal
conditioning devices may be required, such that each signal may be
processed by completely separate signal conditioning apparatus. In
such instances the power supplies are independent in their ability
to relate to the respective signal ground potentials.
Since the present invention utilizes only six matched resistors to
condition a balanced source input, it requires only four matched
resistors to condition a single ended source input. Further,
because of the addition of an inverted circuit placed judiciously
with the input circuit, an almost two fold increase in the
effective interference rejection of the device may be accomplished
for the same resistor matching. As a result, system cost for a
given specification is reduced substantially.
As it is often desirable to adjust the gain of the subject signal
conditioning embodiment, this gain may be adjusted without
affecting the absolute level of unrejected interference. Hence, the
present invention is unique in that common mode forms of
interference are rejected with a rejection ratio that is actually
proportional to the gain so that the interference residuals of each
signal's common mode remains constant in spite of the increased
gain. Only common mode interferences between differentially applied
signals would be proportional to this gain, but these interferences
are typically very small in relation to the normal common mode
interferences.
.[.FIG. 2 depicts.]. .Iadd.FIGS. 2A and 2B depict .Iaddend.a front
end of a typical audio amplifier. A first channel of the audio
amplifier includes a first stage 100 consisting of opamp 101,
resistors 102-106 and capacitor 107 forming a non-inverting opamp
circuit. A second stage includes a highpass active filter circuit
108 and a low pass active filter circuit 116. Switch 124 is
provided for selectively switching the output of highpass filter
108, lowpass filter 116 or the output of first stage 100 directly,
to the input of opamp circuit 125 consisting of opamp 126 and
resistors 127-129.
The second channel of the audio amplifier is similar to the first
channel and includes a first stage 164 consisting of opamp 164,
resistors 137-141 and capacitors 142 and 143 also forming a
non-inverting opamp circuit. The second stage includes highpass
active filter circuit 165 and lowpass active filter circuit 166.
Switch 158 selectively switches the output of highpass filter 165,
lowpass filter 166 or the output of first stage 164 directly, to
the input of inverting opamp circuit 167 consisting of opamp 162
and resistors 159-161. Each of these circuits is well known in the
art and each circuit, therefore, will not be described in detail
below. These circuits will collectively be referred to hereinafter
as the "front end" or preamp of the amplifying system. The output
of opamp circuits 125 and 167 can be input to additional electronic
circuitry 133 for power amplification, noise reduction,
equalization or providing a noise gate function, etc., or any
combination thereof. The outputs of processing circuitry 133 can
then be input to speakers 134.
According to this embodiment of the present invention, signal
source 131 and 136 can consist of any desired source of audio
signals, such as a tuner, tape player, compact disc player, etc.
When operating in stereo, signal source 131 can represent a left
channel and signal source 136 can represent a right channel of an
audio signal, for example. When operating in mono, signal sources
131 and 136 can represent the same signal source. By providing a
non-inverted signal on line 132 via opamp circuit 125 and its
complement on line 163 via inverting opamp circuit 167, it is
possible to achieve twice the output voltage by bridging the
outputs of circuitry 133.
First stage opamp circuits 100 and 164 form buffer amplifiers
providing at their outputs signals proportional to the signals
provided at their inputs, but with a much lower output
impedance.
Highpass filter circuits. 108 and 165 block the low frequency
signals and DC while passing the high frequency signals. These high
frequency signals can be used for driving a high frequency speaker
such as a "tweeter", for example. The output of highpass filter
circuit 108 is provided to terminal A of switch 124 and the output
of highpass filter circuit 165 is provided to terminal A of switch
158.
On the other hand, lowpass filter circuits 116 and 166 block the
high frequency signals while passing the low frequency signals.
These low frequency signals can be used for driving a low frequency
speaker such as a "woofer", for example. The output of lowpass
filter circuit 116 is provided to terminal C of switch 124 and the
output of lowpass filter circuit 166 is provided to terminal C of
switch 158.
Switches 124 and 158 are manual switches used for directing signals
from one of terminals A-C to the respective inputs of opamp
circuits 125 and 167. Opamp circuit 125 provides a non-inverted
signal on output line 132. Inverting opamp circuit 167 provides an
inverted signal on output line 163. The signal on output lines 132
and 163 can then be input to additional electronic circuitry 133
for power amplification, noise reduction, etc. The signals output
from circuitry 133 can then input to right and left speakers 134,
for example, when operating in stereo. When operating in mono, the
outputs of circuitry 133 can be bridged and input to a single
speaker 134.
The "front end" provides most of the voltage amplification in such
an audio amplifier system and electronic circuitry 133 (e.g., a
power amplifier) provides most of the current amplification.
Some of the problems typically encountered by the audio amplifier
circuitry as described above is that the conductors (e.g., coax
cables) tend to introduce interference into the audio signal thus
degrading audio quality. As shown in .[.FIG. 3.]. .Iadd.FIGS. 3A
and 3B.Iaddend., the present invention provides signal conditioning
circuitry, similar to that described above with respect to .[.FIG.
1.]. .Iadd.FIGS. 1A and 1B.Iaddend., that eliminates noise
introduced by the coax cables, without compromising signal quality.
Such benefits are possible using a very minimum amount of
additional circuitry.
.[.FIG. 3 shows.]. .Iadd.FIGS. 3A and 3B show .Iaddend.the typical
audio amplifier depicted in .[.FIG. 2.]. .Iadd.FIGS. 2A and 2B
.Iaddend.including signal conditioning circuitry similar to that
described above with respect to .[.FIG. 1.]. .Iadd.FIGS. 1A and
1B.Iaddend.. Circuit 200, consisting of resistors 230-232,
transistors 233 and 236, zener diode 234 and capacitor 235 and
circuit 201 consisting of resistors 240-242, transistors 243 and
244, zener diode 245 and capacitor 246 provide high impedance
constant current sources for delivering the exact current necessary
to operate the operational amplifiers in the circuitry. Constant
current source circuits 200 and 201 are illustrative of circuits
that can perform this function. Other well known circuitry may also
be used for delivering constant current. As shown, the ground lines
for each of the elements for each channel are tied together and not
to a common ground.
Input amplifier circuits 100 and 164, highpass filters 108 and 165
and lowpass filters 116 and 166 perform the same functions as
described above with respect to .[.FIG. 2.]. .Iadd.FIGS. 2A and
2B.Iaddend.. The present invention includes inverting opamp circuit
202 consisting of resistors 203 and 204 and opamp 205 and inverting
opamp circuit 250 consisting of resistors 251 and 252 and opamp
253. The gain of inverting opamp circuits 202 and 250 can be varied
by varying the resistance ratios of resistors 203 and 204 resistors
251 and 252, respectively.
A basic difference in the circuitry between .[.FIG. 2.].
.Iadd.FIGS. 2A/2B .Iaddend.and .[.FIG. 3.]. .Iadd.FIGS. 3A/3B
.Iaddend.is that the output signals from switches 124 and 158 and
the output of opamp circuits 202 and 250 are summed by differential
amplifiers 125 and 167, respectively, as follows: The signal from
switch 124 is applied to opamp 126 by way of the voltage divider
consisting of resistors 127 and 128 to provide for the expression
of that potential minus the inverted version of that potential
expressed with reference to the input signal reference potential as
presented by the shield conductor of cable 130 by way of opamp 205
and resistor 206. The inverted version of the signal from switch
158 is expressed with reference to the input signal reference
potential as presented by the shield conductor of cable 135 by way
of opamp 253 and resistor 159 to provide for the expression of that
potential minus the signal from switch 158 applied to opamp 162 by
way of resistor 160. As described above with respect to .[.FIG.
2.]. .Iadd.FIGS. 2A and 2B.Iaddend., the output of opamps 126 and
162 may then be further processed by additional electronic
circuitry 134 (e.g., a power amplifier) and output by one or more
speakers 134.
The additional electronic circuitry 133 can be provided as a
separate and distinct unit from preamp circuitry 600 depicted in
.[.FIG. 3.]. .Iadd.FIGS. 3A and 3B.Iaddend.. In the alternative,
the additional electronic circuitry 133 and the preamp or "front
end" circuitry 600 can be provided as a unit in a single case, for
example. Using the circuitry as described in .[.FIG. 3.].
.Iadd.FIGS. 3A and 3B.Iaddend., the present invention is capable of
eliminating noise introduced caused by the conductors and providing
a clean output signal.
In addition to conditioning audio signals in an audio amplifier as
described above, the signal conditioning circuitry of the present
invention can also be provided in other arrangements. For the
description of the following embodiments of the present invention,
the signal conditioning circuitry depicted in .[.FIG. 1.].
.Iadd.FIGS. 1A and 1B .Iaddend.(or the "front end" depicted in
broken line box 600 in .[.FIG. 3.]. .Iadd.FIGS. 3A and 3B.Iaddend.)
is shown in block diagram form as block 403.
As shown in FIG. 4, the fight and left outputs of signal source 400
can be fed through coax cables 401 and 402, respectively, to the
input of preamp 403. As noted above, preamp 403 can consist of the
signal conditioning circuitry depicted in .[.FIG. 1.]. .Iadd.FIGS.
1A and 1B.Iaddend., or can consist of the "front end" circuitry 400
as depicted in .[.FIG. 3.]. .Iadd.FIGS. 3A and 3B.Iaddend.. Preamp
403 provides voltage amplification and eliminates noise in the
signals being processed, without compromising signal quality. The
output of preamp 403 can then be provided to the input of power
amplifier 410. Power amplifier 410 provides current amplification
of the signals on lines 411 and 412 for driving right and left
speakers 420 via lines 413 and 414 when operating in stereo, for
example. When operating in mono, lines 413 and 414 can be bridged
to drive a single speaker.
According to this embodiment of the present invention, preamp 403
can be provided as a separate unit from power amplifier 410, or can
be provided as an integral unit with power amp 410. If preamp 403
is provided as a separate unit, instead of providing individual
power supplies for power amp 403 and power amp 410, power can be
supplied to preamp 403 from power amp 410 via cable 430.
FIG. 5 is similar to FIG. 4, but includes an additional electronic
component 500. Component 500 can consist of an equalizer,
crossover, noise reduction or effects processor circuitry, etc. or
any combination thereof. The present invention can be used in any
state of the art amplification system to eliminate noise without
altering the effect of any other type of processing and without
compromising sound quality in any way.
It is preferable that the majority of the voltage amplification of
the amplifier system of the present invention take place in preamp
403 and that any circuitry that reduces gain be provided after
preamp 403. The majority of the current amplification of the
amplifier system of the present invention occurs in power amp 410.
However, it may also be preferable that speakers 420 include their
own current amplification circuits, particularly if speakers 420
consist of bass speakers. In addition, the present invention makes
it possible to provide such current amplification without the
necessity of isolated power supplies which are costly and lower in
performance. In order to achieve the best results, it is preferable
that if intermediate processing units are provided between the
voltage amplification circuitry and the current amplification
circuitry, that the power supplies for driving each of these units
be isolated power supplies.
The signal conditioning circuitry of the present invention can also
be used for conditioning other types of signals besides audio
signals. For example, as shown in FIG. 6, the video signals from
camera 600 can be fed through coaxial cable 610 to the input of
signal conditioning circuit 620. Signal conditioning circuit 620,
consisting of the signal conditioning circuitry depicted in .[.FIG.
1.]. .Iadd.FIGS. 1A and 1B.Iaddend., suppresses or eliminates noise
or interference introduced by the coaxial cables and provides a
relatively clean output signal. The output signal can then be fed
via coax 630 to video display 635 for immediate display and/or to
remote video recorder 640 for recording. Signal conditioning
circuit 620 can be provided as a unit separate from camera 600,
display 635 and recorder 640, or can be incorporated into an input
or output stage of display 635 and/or recorder 640.
The foregoing has set forth exemplary and preferred embodiments of
the present invention. It will be understood, however, that various
alternatives will occur to those of ordinary skill in the art
without departure from the spirit and scope of the present
invention.
* * * * *