Abstract
M.Ing.
An investigation is conducted into the dynamic behaviour of a music turntable. The
dynamic behaviour of the pickup arm is investigated in detail. The dinamic behaviour of
the pickup arm is important in the design of a turntable because it basicly acts as a
frequency filter. The pickup arm is under damped and is consequently suseptable to
excitation as certain frequencies. The aim of this study is to investigate the dynamic
behaviour of the turntable experimentally and mathematically by simulation. Chapter 1 serves as the introduction to the study. As the study concerns the music turntable, it is opened with a short background study of music and the role which it plays in today’s society. This is followed by an introduction to dynamic systems in general after which it is shown that the music turntable may be classified as a dynamic system. Chapter 2 describes the construction and the functioning of the turntable. The different
components of the turntable is defined and characterised. This is followed by an
investigation into the factors that may have an effect on the dynamic behaviour of the
turntable. Chapter 3 describes how the turntable was modeled. Firstly mechanical modeling in general is investigated. This is followed by a paragraph. concerning analogy in engineering. Simple models to describe the dynamic behaviour of the pickup arm is presented. The effect of different kinds of damping is investigated. A more complex model is developed and described. The mathematical method used to investigate this modelis also described. Chapter 4 describes the experimental work that was performed to verify the simulation "results. The aim of the experimental work is firstly described and. then followed by the description of the general experimental facilities. The excitation, measurement and data - processing is discussed -in detail. The procedure that was followed to find the transfer function of the pickup arm is set out. This is followed by describing the procedure that was followed to find the dynamic behaviour of the pickup arm when it is excited by an impulse, step and a sweep function.
Chapter 5 discusses the experimental and theoretical methods that were used to obtain
the constants which were used in the simulation. Values for most of the constants were obtained experimentally. The constants were obtained by comparing the dynamic behaviour of each component with the dynamic behaviour of a simple system that 'can be solved in the closed form. Chapter 6 discusses the results that were obtained by comparing the experimental and the simulation results, that were obtained for the different excitations. This is followed by a discussion about the complex excitations that are possible when a stilus is pulled along a groove. Chapter 7 consists of two paragraphs. The work that was done is briefly summarised and this is followed by an evaluation of this study.