Automatic Mono Stereo Switch for Audio Amplifiers

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Solution Overview

Problem

Current solutions for coupling monophonic audio sources to stereophonic audio amplifiers often result in undesired sound reproduction, such as silent loudspeakers or signal attenuation, due to incorrect channel connections or lack of automatic switching between mono and stereo modes.

Innovation Solution

A fully automatic stereo/mono switch that analyzes signal levels and cross-correlation between left and right channels to determine the type of audio signal, adjusting weighting factors to correctly route the audio signal to the amplifier stages, ensuring optimal sound reproduction using both loudspeakers for monophonic sources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a monophonic audio source is connected to a single stereo channel, then the connection is simple, but the audio signal is only reproduced via one loudspeaker resulting in undesired sound reproduction

Engineering Contradiction:
Improveconnection simplicityVSAvoidsound reproduction quality
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The system automatically detects whether the connected audio source is monophonic or stereophonic and switches between mono and stereo modes without user intervention. The amplifier monitors the input signal characteristics and autonomously configures the appropriate channel coupling, eliminating the need for manual switching while ensuring correct sound reproduction.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system changes the operational parameter of channel coupling between two states: independent channel operation for stereo signals and coupled channel operation for monophonic signals. This parameter change allows the same amplifier to correctly handle both stereo and monophonic sources by adapting the signal routing configuration based on detected signal characteristics.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If a mechanical switch is used to couple monophonic audio signal to both stereo channels, then the signal can be distributed to both loudspeakers, but the user must manually switch back to stereo mode when connecting a stereo signal source

Engineering Contradiction:
Improvesignal distributionVSAvoidmanual switching requirement
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The system automatically detects whether the connected audio source is monophonic or stereophonic and switches between mono and stereo modes without user intervention. The amplifier monitors the input signal characteristics and autonomously configures the appropriate channel coupling, eliminating the need for manual switching while ensuring correct sound reproduction.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system continuously monitors the input signal characteristics and uses this feedback information to automatically determine whether to operate in mono or stereo mode. By analyzing the signal properties in real-time, the amplifier adjusts its channel coupling configuration accordingly, ensuring optimal performance for the connected source type.

Inventive Principle:
Principle #23Feedback

3Reliability

If Y-cables are used to distribute monophonic audio signal to both stereo channels, then both loudspeakers can reproduce the signal, but the solution lacks intelligence and cannot automatically adapt to different source types

Engineering Contradiction:
Improveloudspeaker utilizationVSAvoidautomatic mode adaptation
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system automatically detects whether the connected audio source is monophonic or stereophonic and switches between mono and stereo modes without user intervention. The amplifier monitors the input signal characteristics and autonomously configures the appropriate channel coupling, eliminating the need for manual switching while ensuring correct sound reproduction.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system changes the operational parameter of channel coupling between two states: independent channel operation for stereo signals and coupled channel operation for monophonic signals. This parameter change allows the same amplifier to correctly handle both stereo and monophonic sources by adapting the signal routing configuration based on detected signal characteristics.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP2648338B1Automatic Mono/Stereo Switch
Publication Date: 2021.09.01 HARMAN BECKER AUTOMOTIVE SYST GMBH
  • EP2648338B1 patent drawingFigure 1~2
  • EP2648338B1 patent drawingFigure 3~4
  • EP2648338B1 patent drawingFigure 5~6

AI summary

An audio device including an automatic or semi-automatic stereo/mono switch is disclosed. In accordance with one example of the present invention the audio device includes a first and a second input for receiving, respectively, a left and a right component of a stereophonic audio signal or, alternatively, for receiving a monophonic audio signal at one of the first or second input. The audio device further includes a first and a second amplifier stage and a stereo/mono switch which is configured to direct either the left and the right component of a stereophonic audio signal received at the first and second input to the first and the second amplifier stage, respectively, or a monophonic signal received at one of the first or second input to both of the first and second amplifier stages. A signal analyzing unit is coupled to the first and second input and configured to automatically detect whether a monophonic signal is present at the first input or the second input and to provide a respective control signal to the stereo/mono switch indicating which one of the first and second input the monophonic signal has been detected at. Further examples of the invention are described further below with reference to the drawings.