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Math Talk

Unknown
edited November 2008 in Strut Central
...so a slice of a pie is an angle, at the same time a whole record is an angle (2 Pi Radians). so the angular velocity as I understand it is the RPM. however, the linear velocity is not constant so if I recorded in an outer groove it would have to be longer to compensate for a higher linear velocity than if I recorded it in the innner-most groove.b, 21b, 21my friend told me that Philips, at one time, made a constant linear velocity turntable that started from the inside. kinda like CD's.b, 21b, 21You ever heard of this?b, 21b, 21 img src="/ubbthreads/images/graemlins/popcorn.gif" alt="" 21

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  • LaserWolfLaserWolf Portland Oregon 11,517 Posts
    I think you can still get turntables that will correct for this. b, 21b, 21Seems like the pitch could be corrected in the mastering as well. b, 21b, 21How many grooves on a record?
  • Options
    Unknown
    oh i dunno, 5 or 6 probably
  • 4YearGraduate4YearGraduate 2,945 Posts
    Fail
  • young_creamyoung_cream 540 Posts
    awut?
  • 4YearGraduate4YearGraduate 2,945 Posts
    HOW MANY GROOVES ARE ON A RECORD?
  • knewjakknewjak 1,231 Posts
    /font1
    Quote:/font1h, 21b, 21HOW MANY GROOVES ARE ON A RECORD? b, 21b, 21h, 21
    b, 21b, 21two, but this one has three... img src="/ubbthreads/images/graemlins/wink.gif" alt="" 21b, 21b, 21
  • JimsterJimster Cruffiton.etsy.com 6,889 Posts
    /font1
    Quote:/font1h, 21b, 21...so a slice of a pie is an angle, at the same time a whole record is an angle (2 Pi Radians). so the angular velocity as I understand it is the RPM. however, the linear velocity is not constant so if I recorded in an outer groove it would have to be longer to compensate for a higher linear velocity than if I recorded it in the innner-most groove.b, 21b, 21my friend told me that Philips, at one time, made a constant linear velocity turntable that started from the inside. kinda like CD's.b, 21b, 21You ever heard of this?b, 21b, 21 img src="/ubbthreads/images/graemlins/popcorn.gif" alt="" 21 b, 21b, 21h, 21
    b, 21b, 21This is why they invented ipods.b, 21b, 21Another 3 sider:b, 21
  • dj_pidj_pi 335 Posts
    /font1
    Quote:/font1h, 21b, 21...so a slice of a pie is an angle, at the same time a whole record is an angle (2 Pi Radians). so the angular velocity as I understand it is the RPM. however, the linear velocity is not constant so if I recorded in an outer groove it would have to be longer to compensate for a higher linear velocity than if I recorded it in the innner-most groove.b, 21b, 21my friend told me that Philips, at one time, made a constant linear velocity turntable that started from the inside. kinda like CD's.b, 21b, 21You ever heard of this?b, 21b, 21 img src="/ubbthreads/images/graemlins/popcorn.gif" alt="" 21 b, 21b, 21h, 21
    b, 21b, 21Time to drop some science.b, 21b, 21You make a very good observation with the angular and linear velocities. You are indeed correct in saying that the angular velocity of a record is a measurement in RPM while the linear velocity would be changing along different points of the record.b, 21b, 21Now the part of different velocities for a record... b, 21b, 21You have to understand a bit at what you're trying to do when playing audio from a record. A record (in most cases) is a single groove per each side which runs continuously from the run-in groove on the outer-most part of the record to the run-out groove being the inner most part of a record. Along the way, this groove has microscopic etchings which 'bounce' a stylus left and right, as well as up and down (looking at a record from an overhead perpsective). Depending on the cartridge (let's say it's a magnetic cartidge) while the stylus bounces around according to the grooves, the other end of the stylus is a small magnet placed between two windings of copper coils. The magnet moving through the copper coils is a phenomena which induces electricity (Maxwell's equations) typically in the millivolts range. Boost that signal up a million times...and you got audible sound in decibels (dB).b, 21http://en.wikipedia.org/wiki/Magnetic_cartridgeb, 21b, 21Now knowing how the sound is made, you will soon realize that making an accurate recording all depends on the speed of the stylus passing through the groove...which is your angular velocity! Whether you are at the outer part of the record, or the inner part of the record, you're angular velocity will always be the same, namely 33 RPM or 45 RPM (sometimes 78) granted your pitch is set to 0%. b, 21b, 21The linear velocity of a point on the record translates more into how much audio 'information' can you etch on that particular part of the record. On the outer part, the position (remember...not the angle!) of the record will definitely be traveling faster compared to the inner position, but this translates into more length for etching on the outer part than the inner.b, 21b, 21Your idea of a linear velocity 'turntable' is actually the first type of phonograph that Thomas Edison invented which used cylindrical tubes with the etchings on the outside. For linear velocity on a modern day turntable, the turntable would have to be aware of where it is on the record and adjust it's speed accordingly. It would also require a disc pressed specifically for this type of application.b, 21http://en.wikipedia.org/wiki/Phonograph#Disc_versus_cylinder_as_a_recording_mediumb, 21b, 21The 'adjustment' that people have mentioned is really the anti-skate force. (Yeah...that little dial that no one has any idea what it is and you just set to 0...me included). What this is an adjustment to correct the stylus a bit due to the centripical force. Think of it this way... When you get on or off the express way, and you're on the ramp in a large loop you experience centripical force. While your car is going along the road...your body tends to go away from the car. Your stylus experiences this same force! To compensate, you adjust the anti-skate to a point where your stylus doesn't appear to 'bend' to the right as much. If you put too much anti-skate you stylus will 'bend' to the left a bit. If you want a healthy and happy needle, you should adjust this.b, 21b, 21If you have any more questions...hollerate...b, 21b, 21 b, 21b, 21Enough nerdom...who's got some raer funk 45's for me?
  • djdazedjdaze 3,099 Posts
    I think you mean centrifugal force
  • dj_pidj_pi 335 Posts
    Yes indeed!b, 21b, 21I stand corrected. Thanks.
  • LaserWolfLaserWolf Portland Oregon 11,517 Posts
    /font1
    Quote:/font1h, 21b, 21/font1Quote:/font1h, 21b, 21...so a slice of a pie is an angle, at the same time a whole record is an angle (2 Pi Radians). so the angular velocity as I understand it is the RPM. however, the linear velocity is not constant so if I recorded in an outer groove it would have to be longer to compensate for a higher linear velocity than if I recorded it in the innner-most groove.b, 21b, 21my friend told me that Philips, at one time, made a constant linear velocity turntable that started from the inside. kinda like CD's.b, 21b, 21You ever heard of this?b, 21b, 21 img src="/ubbthreads/images/graemlins/popcorn.gif" alt="" 21 b, 21b, 21h, 21
    b, 21b, 21Time to drop some science.b, 21b, 21You make a very good observation with the angular and linear velocities. You are indeed correct in saying that the angular velocity of a record is a measurement in RPM while the linear velocity would be changing along different points of the record.b, 21b, 21Now the part of different velocities for a record... b, 21b, 21You have to understand a bit at what you're trying to do when playing audio from a record. A record (in most cases) is a single groove per each side which runs continuously from the run-in groove on the outer-most part of the record to the run-out groove being the inner most part of a record. Along the way, this groove has microscopic etchings which 'bounce' a stylus left and right, as well as up and down (looking at a record from an overhead perpsective). Depending on the cartridge (let's say it's a magnetic cartidge) while the stylus bounces around according to the grooves, the other end of the stylus is a small magnet placed between two windings of copper coils. The magnet moving through the copper coils is a phenomena which induces electricity (Maxwell's equations) typically in the millivolts range. Boost that signal up a million times...and you got audible sound in decibels (dB).b, 21http://en.wikipedia.org/wiki/Magnetic_cartridgeb, 21b, 21Now knowing how the sound is made, you will soon realize that making an accurate recording all depends on the speed of the stylus passing through the groove...which is your angular velocity! Whether you are at the outer part of the record, or the inner part of the record, you're angular velocity will always be the same, namely 33 RPM or 45 RPM (sometimes 78) granted your pitch is set to 0%. b, 21b, 21The linear velocity of a point on the record translates more into how much audio 'information' can you etch on that particular part of the record. On the outer part, the position (remember...not the angle!) of the record will definitely be traveling faster compared to the inner position, but this translates into more length for etching on the outer part than the inner.b, 21b, 21Your idea of a linear velocity 'turntable' is actually the first type of phonograph that Thomas Edison invented which used cylindrical tubes with the etchings on the outside. For linear velocity on a modern day turntable, the turntable would have to be aware of where it is on the record and adjust it's speed accordingly. It would also require a disc pressed specifically for this type of application.b, 21http://en.wikipedia.org/wiki/Phonograph#Disc_versus_cylinder_as_a_recording_mediumb, 21b, 21The 'adjustment' that people have mentioned is really the anti-skate force. (Yeah...that little dial that no one has any idea what it is and you just set to 0...me included). What this is an adjustment to correct the stylus a bit due to the centripical force. Think of it this way... When you get on or off the express way, and you're on the ramp in a large loop you experience centripical force. While your car is going along the road...your body tends to go away from the car. Your stylus experiences this same force! To compensate, you adjust the anti-skate to a point where your stylus doesn't appear to 'bend' to the right as much. If you put too much anti-skate you stylus will 'bend' to the left a bit. If you want a healthy and happy needle, you should adjust this.b, 21b, 21If you have any more questions...hollerate...b, 21b, 21 b, 21b, 21Enough nerdom...who's got some raer funk 45's for me? b, 21b, 21h, 21b, 21b, 21 img src="/ubbthreads/images/graemlins/know.gif" alt="" 21
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    Unknown
    dj pi...hes thorough and complete img src="/ubbthreads/images/graemlins/jonnygraem.gif" alt="" 21b, 21b, 21thanks and how about this, you ever hear of DJ using the split cue?b, 21b, 21I was told that some DJ cue up one turntable in one ear and the other in the other ear of their headphones. I better check to see if my mixer has this feature.b, 21b, 21peaceb, 21b, 21lilmonstu
  • DJ_WubWubDJ_WubWub 874 Posts
    /font1
    Quote:/font1h, 21b, 21b, 21thanks and how about this, you ever hear of DJ using the split cue?b, 21b, 21h, 21
    b, 21b, 21my mixer has that feature (Pioneer DJM600) but I have tried it and just cant get used to hearing one track in each ear it confuzzes me. Maybe if I got used to it though it may help my mixing.
  • UnconSciUnconSci 824 Posts
    split cue helps in getting your levels right... thats about it unless you have no monitors.
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