SDOF in Hi-Fi Amplification

Abstract

This study explores damping and voicing strategies in Hi-Fi amplification through the lens of Single Degree of Freedom (SDOF) modelng. By bridging mechanical and electrical domains, the work introduces the SDOF, Voltage Amplification Stage (VAS), and a Compound Biasing Clamp — a distributed bias stabilization topology with clamp logic across VAS tail, lead, and mirror nodes. Filters shape soak curvature, Zeta behavior, and psychoacoustic contour through multi-stage interaction. The subsonic clamp is Zeta (ζ) tuneable and validates its perceptual impact on musical decay and excursion symmetry. The concept of the Zeta Saddle is introduced as a psychoacoustic sweet spot, supported by SPICE overlays and annotated transient traces. The study further demonstrates integration into orthodox amplifier designs, including modified Blameless topology, and highlights added value for spiderless full-range drivers via subsonic arresting. This dual-domain approach offers a new framework for amplifier voicing, combining structural dynamics with electrical damping to shape musical response.

Introduction

The exploration of damping and voicing in audio amplification has traditionally focused on distortion metrics, bandwidth, and stability. Yet beneath these familiar parameters lies a subtler dimension — one shaped by decay, excursion symmetry, and psychoacoustic warmth. This study investigates that dimension through the lens of SDOF systems, applying principles more commonly found in mechanical domains to the electrical behavior of amplifier feedback loops.

This paper explores the interplay between damping behavior and voicing in high-fidelity amplifier design, focusing on systems governed by a single dominant degree of freedom. Using loop snapshots, behavioral Zeta estimates, and psychoacoustic analysis, I examine how compensation strategies — including High Frequency-gated (HF-gated) bias clamps and compound anchor stacks — shape transient decay, excursion recovery, and perceived musicality. The study highlights how subtle shifts in damping ratio (ζ) influence voicing integrity, and proposes a framework for embedding musical damping into loop-stable topologies.

What makes this study unusual — and perhaps at a forefront— is its focus on bias management and framing of the VAS as a controllable SDOF system. While related concepts exist in mechanical damping and dominant pole shaping, the integration of loop-shaped Zeta (ζ), musical decay control, and stacked bias voicing is rarely documented in audio literature.