Stereo audio system and method
A circuit receives a first input signal and a second input signal, and provides three driving signals to three output wires, respectively. A first driving signal is provided to a first output wire, and is based on a difference between the first input signal and the second input signal. A second driving signal is provided to a second output wire, and is based on a sum of the first input signal and the second input signal. A third driving signal is provided to a third output wire, and is based on an inverse of the first driving signal. A first output signal between the first output wire and the second output wire is based on the second input signal. A second output signal between the third output wire and the second output wire is based on the first input signal.
1. A circuit, comprising:
a first output wire, a second output wire, and a third output wire, wherein the circuit is configured to:
receive a first input signal R and a second input signal L;
provide a first driving signal to the first output wire, the first driving signal being a linear function of the difference between the input signal R and the input signal L;
provide a second driving signal to the second output wire, the second driving signal being a linear function of the sum of the input signal R and L; and
provide a third driving signal to the third output wire, the third driving signal having a magnitude of the first driving signal and having an opposite polarity with respect to the first driving signal;
provide a first output signal between the first output wire and the second output wire, the first output signal being a linear function of the input signal L and not a function of the input signal R; and
provide a second output signal between the third output wire and the second output wire, the second output signal being a linear function of the input signal and not a function of the input signal L;
wherein the circuit is configured to:
provide a first driving signal −a(R−L) to the first output wire;
provide a second driving signal −a(R+L) to the second output wire; and
provide a third driving signal −a(L−R) to the third output wire, where a is a constant;
wherein the circuit is configured to:
provide a first output signal 2 bL between the first output wire and the second output wire; and
provide a second output signal 2 bR between the third output wire and the second output wire, where b is a constant;
wherein the circuit comprises:
a first inverting amplifier for receiving the first input signal R and providing a signal −R;
a second inverting amplifier for receiving the second input signal L and providing a signal −L;
a first summing amplifier for receiving −R and L signals and producing a signal a(R−L);
a second summing amplifier for receiving −R and −L signals and producing a signal a(R+L); and
a third summing amplifier for receiving −L and R signals and producing a signal a(L−R).
2. The circuit of claim 1 , wherein:
the first output wire is configured to be coupled to a positive terminal of a first speaker;
the second output wire is configured to be coupled to a negative terminal of the first speaker and to a negative terminal of a second speaker; and
the third output wire is configured to be coupled to a positive terminal of the second speaker,
whereby the circuit is configured to:
provide a first output signal based on 2 bL to the first speaker without blocking capacitors; and
provide a second output signal based on 2 bR to the second speaker without blocking capacitors being connected to the speakers.
3. The circuit of claim 1 , wherein the circuit further comprises:
a first power amplifier configured to receive the signal a(R−L) from the first summing amplifier and to produce a signal −b(R−L) to the first output wire;
a second power amplifier configured to receive the signal a(R+L) from the second summing amplifier and to produce a signal −b(R+L) to the second output wire; and
a third power amplifier configured to receive the signal a(L−R) from the third summing amplifier and to produce a signal −b(L−R) to the third output wire.
4. The circuit of claim 1 , wherein the circuit comprises a digital signal processor configured to:
receive a first input signal R and a second input signal L;
provide a first signal a(R−L) to the first output wire;
provide a second signal a(R+L) to the second output wire; and
provide a third signal a(L−R) to the third output wire.
5. The circuit of claim 1 , wherein the circuit further comprises:
a first power amplifier configured to receive the first signal a(R−L) from the digital signal processor and to produce a signal −b(R−L) to the first output wire;
a second power amplifier configured to receive the second signal a(R+L) from the digital signal processor and to produce a signal −b(R+L) to the second output wire; and
a third power amplifier configured to receive the third signal a(L−R) from the digital signal processor and to produce a signal −b(L−R) to the third output wire.
6. A circuit, comprising:
a first output wire, a second output wire, and a third output wire,
wherein the circuit is configured to:
receive a first input signal R and a second input signal L;
provide a first driving signal to the first output wire, the first driving signal based on a difference between the first input signal and the second input signal;
provide a second driving signal to the second output wire, the second driving signal based on a sum of the first input signal and the second input signal;
provide a third driving signal to the third output wire, the third driving signal based on an inverse of the difference between the first input signal and the second input signal;
wherein the circuit is configured to:
provide a first output signal between the first output wire and the second output wire; and
provide a second output signal between the third output wire and the second output wire;
wherein the circuit comprises:
a first inverting amplifier for receiving the first input signal R and providing a signal −R;
a second inverting amplifier for receiving the second input signal L and providing a signal −L;
a first summing amplifier for receiving −R and L signals and producing a signal a(R−L);
a second summing amplifier for receiving −R and −L signals and producing a signal a(R+L); and
a third summing amplifier for receiving −L and R signals and producing a signal a(L−R), where a is a constant.
7. The circuit of claim 6 , wherein the circuit further comprises:
a first power amplifier configured to receive the signal a(R−L) from the first summing amplifier and to produce a signal −b(R−L) to the first output wire;
a second power amplifier configured to receive the signal a(R+L) from the second summing amplifier and to produce a signal −b(R+L) to the second output wire; and
a third power amplifier configured to receive the signal a(L−R) from the third summing amplifier and to produce a signal −b(L−R) to the third output wire.
8. The circuit of claim 6 , wherein the circuit comprises a digital signal processor configured to:
receive a first input signal R and a second input signal L;
provide a first signal based on a(R−L) to the first output wire;
provide a second signal based on a(R+L) to the second output wire; and
provide a third signal based on a(L−R) to the third output wire, where a is a constant.
9. The circuit of claim 8 , wherein the circuit further comprises:
a first power amplifier configured to receive the signal a(R−L) from the digital signal processor and to produce a signal −b(R−L) to the first output wire;
a second power amplifier configured to receive the signal a(R+L) from the digital signal processor and to produce a signal −b(R+L) to the second output wire; and
a third power amplifier configured to receive the signal a(L−R) from the digital signal processor and to produce a signal −b(L−R) to the third output wire.
10. A stereo audio system, comprising:
a first input audio signal R;
a second input audio signal L;
a driver circuit having a first output wire, a second output wire, and a third output wire,
wherein the driver circuit is configured to:
receive the first input audio signal R and the second input audio signal L;
provide a first driving signal to the first output wire, the first driving signal based on a difference between the first input audio signal and the second input audio signal;
provide a second driving signal to the second output wire, the second driving signal based on a sum of the first input audio signal and the second input audio signal;
provide a third driving signal to the third output wire, the third driving signal based on an inverse of the difference between the first input audio signal and the second input audio signal;
a first speaker having a positive terminal coupled to the first output wire and a negative terminal coupled to the second output wire;
a second speaker having a positive terminal coupled to the third output wire and a negative terminal coupled to the second output wire;
whereby:
the first speaker is configured to receive a first output signal based on twice the second input audio signal 2 L; and
the second speaker is configured to receive a second output signal based on twice the first input audio signal 2 R;
wherein the driver circuit comprises:
a first inverting amplifier for receiving the first input audio signal R and providing a signal −R;
a second inverting amplifier for receiving the second input audio signal L and providing a signal −L;
a first summing amplifier for receiving −R and L signals and producing a signal (R−L);
a second summing amplifier for receiving −R and −L signals and producing a signal (R+L); and
a third summing amplifier for receiving −L and R signals and producing a signal (L−R).
11. The system of claim 10 , wherein the driver circuit further comprises:
a first power amplifier with an amplification of −1× and configured to receive the signal (R−L) from the first summing amplifier and to produce a signal −(R−L) to the first output wire;
a second power amplifier with an amplification of −1×and configured to receive the signal (R+L) from the second summing amplifier and to produce a signal −(R+L) to the second output wire; and
a third power amplifier with an amplification of −1×and configured to receive the signal (L−R) from the third summing amplifier and to produce a signal −(L−R) to the third output wire.