Record Player Physics

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Homework Help Overview

The discussion centers around the physics of vibrations in record players, specifically within the context of a Dynamics and Vibrations class project. Participants explore the relevant equations and concepts related to vibrational modes, audio signal distortion, and the mechanics of phono cartridges.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants inquire about sources of vibrations and resonances in record players, the encoding of audio information in grooves, and the mechanics of the needle and cartridge system. There are discussions about the relevance of Fourier analysis and mass-spring-damper systems.

Discussion Status

The conversation is ongoing, with participants sharing insights and prompting further exploration of the topic. Some guidance has been offered regarding potential sources of information and relevant concepts, but no consensus has been reached on specific equations or methods.

Contextual Notes

Participants are navigating a broad topic with various aspects of vibration physics, and there is an acknowledgment of the complexity involved in understanding the interplay between mechanical and electrical systems in record players.

OutdoorInnovator
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Hi, I have a project for my Dynamics and Vibrations class and I wanted to do it on the vibrations of a record player. Does anyone know what equations would be most relevant? I know this is a very general question but the project is large so I'm still figuring it out! Any thoughts are super appreciated.
 
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Welcome to PF.

What have you found in your research so far? What would be some of the sources of vibrations, and what-all could contribute to resonances? What would different vibrational modes do in terms of distorting the audio pickup/playback signal?
 
berkeman said:
Welcome to PF.

What have you found in your research so far? What would be some of the sources of vibrations, and what-all could contribute to resonances? What would different vibrational modes do in terms of distorting the audio pickup/playback signal?
I've found that the needle moves along the ridges which causes it to move up and down and move a magnet attached to the cantilever to vibrate between 2 coils to convert the mechincal energy to electrical energy
 
Sure, but how is that audio information encoded in those grooves? Up/down or sideways or a combination? How is stereo information encoded in a single groove with a single pickup needle?

And what are the most common vibration noise sources in such a mechanical system?
 
its a combination but I believe up and down for non-stereo systems
 
berkeman said:
What have you found in your research so far? What would be some of the sources of vibrations, and what-all could contribute to resonances? What would different vibrational modes do in terms of distorting the audio pickup/playback signal?
berkeman said:
And what are the most common vibration noise sources in such a mechanical system?
 
Hi @OutdoorInnovator , and welcome to PF!
You may want to check out information from the phono cartridge manufacturers, i can think of Ortofon, Shure, Grado off the top of my head. I haven't looked, but they may have tech info on their websites.

I'm not sure of your academic level. You might find Fourier analysis interesting, this is a way of breaking complex waveforms (like music) into sums of simple sine waves.
 
OutdoorInnovator said:
I have a project for my Dynamics and Vibrations class
Since Dynamics and Vibration, you should look up mass-spring-damper system, and mechanical-electrical transducers.

The cartridge pickup is a mechanical system that vibrates, with the attached coil connected to an electrical system that can amplify the signal. Or the 'needle' can be directly connected to a horn to produce sound waves.

Apparently, this is a simplified model. ( an electrical representation of the mass-spring-damper )
https://en.wikibooks.org/wiki/Engineering_Acoustics/Phonograph_Sound_Reproduction
 

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