Sound Matching an Analogue Levelling Amplifier Using the Newton-Raphson Method

Fuente: arXiv
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Autori principali: Yu, Chin-Yun, Fazekas, György
Natura: Preprint
Pubblicazione: 2025
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author Yu, Chin-Yun
Fazekas, György
author_facet Yu, Chin-Yun
Fazekas, György
contents Automatic differentiation through digital signal processing algorithms for virtual analogue modelling has recently gained popularity. These algorithms are typically more computationally efficient than black-box neural networks that rely on dense matrix multiplications. Due to their differentiable nature, they can be integrated with neural networks and jointly trained using gradient descent algorithms, resulting in more efficient systems. Furthermore, signal processing algorithms have significantly fewer parameters than neural networks, allowing the application of the Newton-Raphson method. This method offers faster and more robust convergence than gradient descent at the cost of quadratic storage. This paper presents a method to emulate analogue levelling amplifiers using a feed-forward digital compressor with parameters optimised via the Newton-Raphson method. We demonstrate that a digital compressor can successfully approximate the behaviour of our target unit, the Teletronix LA-2A. Different strategies for computing the Hessian matrix are benchmarked. We leverage parallel algorithms for recursive filters to achieve efficient training on modern GPUs. The resulting model is made into a VST plugin and is open-sourced at https://github.com/aim-qmul/4a2a.
format Preprint
id arxiv_https___arxiv_org_abs_2509_10706
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Sound Matching an Analogue Levelling Amplifier Using the Newton-Raphson Method
Yu, Chin-Yun
Fazekas, György
Audio and Speech Processing
Sound
Systems and Control
Automatic differentiation through digital signal processing algorithms for virtual analogue modelling has recently gained popularity. These algorithms are typically more computationally efficient than black-box neural networks that rely on dense matrix multiplications. Due to their differentiable nature, they can be integrated with neural networks and jointly trained using gradient descent algorithms, resulting in more efficient systems. Furthermore, signal processing algorithms have significantly fewer parameters than neural networks, allowing the application of the Newton-Raphson method. This method offers faster and more robust convergence than gradient descent at the cost of quadratic storage. This paper presents a method to emulate analogue levelling amplifiers using a feed-forward digital compressor with parameters optimised via the Newton-Raphson method. We demonstrate that a digital compressor can successfully approximate the behaviour of our target unit, the Teletronix LA-2A. Different strategies for computing the Hessian matrix are benchmarked. We leverage parallel algorithms for recursive filters to achieve efficient training on modern GPUs. The resulting model is made into a VST plugin and is open-sourced at https://github.com/aim-qmul/4a2a.
title Sound Matching an Analogue Levelling Amplifier Using the Newton-Raphson Method
topic Audio and Speech Processing
Sound
Systems and Control
url https://arxiv.org/abs/2509.10706