对比多种数字滤波器离散化方法,为黑胶唱片播放校准提供技术参考。
A Survey of Methods for the Discretization of Phonograph Record Playback Filters

- 分析连续时间滤波器到离散时间的转换方法
- 量化不同方法在奈奎斯特频率附近的响应偏差
- 适合开发数字黑胶播放系统的工程师参考
自1924年电气录音技术问世以来,黑胶唱片通过非均匀频率响应提升信息密度并改善信噪比。为还原平坦信号,播放时需应用反向均衡曲线。1953年前,各唱片公司及不同时期使用的播放曲线各异,因此需支持多种均衡的设备。该校正可通过模拟硬件或数字处理实现,数字方案成本更低、更灵活,但需将连续时间曲线转换为离散时间,此过程在奈奎斯特频率附近会产生响应偏差。本文探讨了多种离散化方法在黑胶播放均衡中的应用,并量化其性能表现,旨在为数字播放均衡系统开发者提供实用参考。
原文摘要 · Abstract (English)
Since the inception of electrical recording for phonograph records in 1924, records have been intentionally cut with a non-uniform frequency response to maximize the information density on a disc and to improve the signal-to-noise ratio. To reproduce a nominally flat signal within the available bandwidth, the effects of this cutting curve must be undone by applying an inverse curve on playback. Until 1953, with the introduction of what has become known as the RIAA curve, the playback curve required for any particular disc could vary by record company and over time. As a consequence, anyone seeking to hear or restore the information on a disc must have access to equipment that is capable of implementing multiple playback equalizations. This correction may be accomplished with either analog hardware or digital processing. The digital approach has the advantages of reduced cost and expanded versatility, but requires a transformation from continuous time, where the original curves are defined, to discrete time. This transformation inevitably comes with some deviations from the continuous-time response near the Nyquist frequency. There are many established methods for discretizing continuous-time filters, and these vary in performance, computational cost, and inherent latency. In this work, several methods for performing this transformation are explored in the context of phonograph playback equalization, and the performance of each approach is quantified. This work is intended as a resource for anyone developing systems for digital playback equalization or similar applications that require approximating the response of a continuous-time filter digitally.
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