Velocity is not Amplitude - Pick Up Cartridges
Printed From: Graham Slee Hifi System Components
Category: DIY AUDIO
Forum Name: DIY Audio questions and answers
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Topic: Velocity is not Amplitude - Pick Up Cartridges
Posted By: Graham Slee
Subject: Velocity is not Amplitude - Pick Up Cartridges
Date Posted: 25 Jul 2016 at 6:30am
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For all those people who have said in the past, are saying now, and will say in the future: "the output of a magnetic phono cartridge is flat" go and write on the blackboard 100 times ... Velocity is not Amplitude Magnetic cartridges called a constant velocity device do not produce a flat amplitude output. Their output is proportional to velocity (you can call it speed to make it easier to understand). Bass frequencies rise slowly - the velocity is low - not very fast. The electrical output will be small. Treble frequencies rise fast - the velocity is high - very fast. The electrical output will be high. So if we take a frequency response plot of frequency versus amplitude what will be its shape? Not flat! It is a rising slope - left side low - right side high - with an incline of 45 degrees. That isn't flat. This is why a phono preamp with EQ (equalisation) is necessary which folds the plot down at 45 degrees to make it flat. When that is done you will find the output from a record isn't flat either. The response kicks up to the left at 50Hz, is flat to 500 Hz, kicks down to 2122Hz, and is flat from there to wherever the mastering suite decided to "cut off". So inside the phono preamp there is additional circuitry to correct that too. Got it? ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Replies:
Posted By: IntempestaNocte
Date Posted: 25 Jul 2016 at 6:00pm
Thanks Graham. I did know that a magnetic cartridges output wasn't flat, although it does sometimes slip my mind  . I have heard the phrase 'rising response' used many times by many different people but this is the first thing that I have read where anyone has actually bothered to explain what that actually means. And using terms that anyone who remembers doing a science GCSE should be able to understand. There is a big difference between knowing something and understanding something and now I actually understand.------------- Scott AT150MLX > Audiomods Series V Standard > Rega RP6 > Accession MM > Marantz PM6005 > KEF Q100 / Solo UL > HD540II. Voyager, Bitzie, AgSat90. |
Posted By: ServerBaboon
Date Posted: 26 Jul 2016 at 5:38pm
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Has someone incurred a 'whole can of woop ass' ? ------------- Steve ------------- Various bits of GSP Kit ..well two so far, unless you count the cables that is. |