Reactive Load Box Impedance Matching for Vacuum Tube Amplifiers

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Solution Overview

Problem

Existing load boxes with fixed impedance characteristics can cause unintended changes in sound tone when the impedance of a vacuum tube amplifier does not match the reactive load, leading to suboptimal sound quality.

Innovation Solution

A load box with a reactive load that simulates impedance characteristics of a speaker cabinet, featuring adjustable impedance patterns in different frequency bands and a correction unit, such as an equalizer, to adjust and improve the sound quality by matching the impedance characteristics of the vacuum tube amplifier.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reactive load with fixed impedance characteristics is used, then the load box can simulate speaker cabinet impedance, but unintended changes in sound tone occur when vacuum tube amplifier impedance does not match the reactive load impedance

Engineering Contradiction:
Improvesound quality stabilityVSAvoidimpedance matching adaptability
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the impedance characteristics of the reactive load adjustable rather than fixed. The operation element allows users to select from multiple impedance characteristic patterns, enabling the reactive load to adapt its impedance to match different vacuum tube amplifier types. This resolves the contradiction by allowing the system to maintain reliable sound quality across various amplifier configurations through dynamic impedance adjustment.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the impedance parameters of the reactive load to match different vacuum tube amplifier types. By providing multiple impedance characteristic patterns that correspond to different amplifier types, the system can adjust key impedance parameters to achieve optimal matching, thereby preventing unintended sound tone changes while maintaining compatibility with various amplifiers.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If impedance characteristics of the reactive load are adjusted to match different vacuum tube amplifier types, then sound quality stability is improved, but the device complexity increases due to multiple impedance pattern selections

Engineering Contradiction:
Improvesound quality stabilityVSAvoidimpedance adjustment mechanism
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent achieves universality by designing the reactive load to handle multiple impedance characteristic patterns within a single device. Rather than requiring separate reactive loads for different amplifier types, one multi-functional reactive load with selectable impedance patterns can work with various vacuum tube amplifier types, reducing overall system complexity while maintaining sound quality stability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent creates simplified copies of speaker cabinet impedance characteristics through pre-defined impedance characteristic patterns. Instead of requiring complex real-time impedance matching circuits, the system uses predetermined impedance patterns that replicate the essential characteristics needed for different amplifier types, thereby achieving reliable sound quality with simpler device architecture.

Inventive Principle:
Principle #26Copying

3Device complexity

If the reactive load uses fixed impedance characteristics, then the device complexity is reduced, but the correction unit cannot effectively correct sound quality across different amplifier types

Engineering Contradiction:
Improveimpedance characteristic structureVSAvoidsound quality correction accuracy
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The correction unit operates dynamically by receiving selection information about the vacuum tube amplifier type and adjusting its correction characteristics accordingly. Rather than using fixed correction parameters, the correction unit adapts its frequency response and impedance characteristics to match the selected amplifier type, thereby achieving high sound quality correction accuracy without requiring overly complex hardware structures.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP3651355B1Load box and sound quality improving method
Publication Date: 2021.05.05 ROLAND CORP
  • EP3651355B1 patent drawingFigure 1
  • EP3651355B1 patent drawingFigure 2~3
  • EP3651355B1 patent drawingFigure 4

AI summary

To improve voice sound quality using a vacuum tube amplifier. A reactive load that has impedance characteristics, in which impedance characteristics in a first frequency band includes a first impedance characteristic pattern selected from a plurality of first impedance characteristic pattern candidates on the basis of a type of a vacuum tube amplifier, and impedance characteristics in a second frequency band includes a second impedance characteristic pattern selected from a plurality of second impedance characteristic patterns on the basis of the type of the vacuum tube amplifier, outputs a signal that responds to a sound signal output from the vacuum tube amplifier in accordance with the impedance characteristics and performs correction on an output signal of the reactive load.