What's the output of a record needle playing an out-of-speed record





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I'm very interested in vinyl records and analog music, and the belt of my turntable got loose. Upon such situation it piqued my curiosity, what is the output signal at the end of the arm cartridge wires for a known waveshape if the speed is not the correct one.



Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?



I'm not considering the filters that the needle might apply on the signal, whether it is a low pass, band pass, or high pass nor any other impedances that might alter the signal in any circumstance, just a supposedly ideal needle and cartridge.






brushless-dc-motor







share|improve this question











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    1












    $begingroup$


    I'm very interested in vinyl records and analog music, and the belt of my turntable got loose. Upon such situation it piqued my curiosity, what is the output signal at the end of the arm cartridge wires for a known waveshape if the speed is not the correct one.



    Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?



    I'm not considering the filters that the needle might apply on the signal, whether it is a low pass, band pass, or high pass nor any other impedances that might alter the signal in any circumstance, just a supposedly ideal needle and cartridge.






    brushless-dc-motor







    share|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I'm very interested in vinyl records and analog music, and the belt of my turntable got loose. Upon such situation it piqued my curiosity, what is the output signal at the end of the arm cartridge wires for a known waveshape if the speed is not the correct one.



      Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?



      I'm not considering the filters that the needle might apply on the signal, whether it is a low pass, band pass, or high pass nor any other impedances that might alter the signal in any circumstance, just a supposedly ideal needle and cartridge.






      brushless-dc-motor







      share|improve this question











      $endgroup$




      I'm very interested in vinyl records and analog music, and the belt of my turntable got loose. Upon such situation it piqued my curiosity, what is the output signal at the end of the arm cartridge wires for a known waveshape if the speed is not the correct one.



      Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?



      I'm not considering the filters that the needle might apply on the signal, whether it is a low pass, band pass, or high pass nor any other impedances that might alter the signal in any circumstance, just a supposedly ideal needle and cartridge.






      brushless-dc-motor




      brushless-dc-motor






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 58 mins ago









      Dave Tweed♦

      123k9152266




      123k9152266










      asked 1 hour ago









      Gabriel SantosGabriel Santos

      163




      163






















          3 Answers
          3






          active

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          3












          $begingroup$


          Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?




          The pitch and tempo will change in proportion to the speed change. At 33 RPM it would already be musically flat as the correct speed is 331/3 RPM. A 1 kHz test tone - common on test records - would, at 33 RPM, give off $ frac {33}{33.33} text {kHz} $.



          The sinewave would remain a sinewave but stretched in time and, therefore, a lower pitch.






          share|improve this answer











          $endgroup$





















            2












            $begingroup$

            Changing the speed of the platter simply affects how fast the groove is moving under the needle, nothing else.



            A sine wave with the time axis compressed or expanded is still a sine wave. In fact, since the groove is a direct mechanical representation of the original complex waveform, you still get the same waveform simply compressed or expanded in time.






            share|improve this answer









            $endgroup$













            • $begingroup$
              Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
              $endgroup$
              – Gabriel Santos
              56 mins ago










            • $begingroup$
              It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
              $endgroup$
              – Dave Tweed♦
              55 mins ago



















            2












            $begingroup$

            To really simplify, a record has wiggles in the groove that correspond to the recorded sound pressure. (This ignores stereo, and any compounding, but it answers your question).



            Events are recorded onto that wiggly grove as they happen -- you can think of the groove as a picture of the sound, with the time domain turned into events happening as the needle follows the groove.



            If you play the record slower, all the events happen more slowly -- the singer sings slower and deeper, the orchestra does too, etc. Speeding it up does the opposite -- a normal recording, sped up, sounds like a hyperactive chipmunk.






            share|improve this answer











            $endgroup$













            • $begingroup$
              I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
              $endgroup$
              – Toor
              49 mins ago












            Your Answer





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            3 Answers
            3






            active

            oldest

            votes








            3 Answers
            3






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            3












            $begingroup$


            Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?




            The pitch and tempo will change in proportion to the speed change. At 33 RPM it would already be musically flat as the correct speed is 331/3 RPM. A 1 kHz test tone - common on test records - would, at 33 RPM, give off $ frac {33}{33.33} text {kHz} $.



            The sinewave would remain a sinewave but stretched in time and, therefore, a lower pitch.






            share|improve this answer











            $endgroup$


















              3












              $begingroup$


              Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?




              The pitch and tempo will change in proportion to the speed change. At 33 RPM it would already be musically flat as the correct speed is 331/3 RPM. A 1 kHz test tone - common on test records - would, at 33 RPM, give off $ frac {33}{33.33} text {kHz} $.



              The sinewave would remain a sinewave but stretched in time and, therefore, a lower pitch.






              share|improve this answer











              $endgroup$
















                3












                3








                3





                $begingroup$


                Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?




                The pitch and tempo will change in proportion to the speed change. At 33 RPM it would already be musically flat as the correct speed is 331/3 RPM. A 1 kHz test tone - common on test records - would, at 33 RPM, give off $ frac {33}{33.33} text {kHz} $.



                The sinewave would remain a sinewave but stretched in time and, therefore, a lower pitch.






                share|improve this answer











                $endgroup$




                Say the record was mean to play sin(wt), a pure sine wave, at 33rpm, then, because of a loosen belt or any other reason, it rotates at a different RPM, how to calculate the changes in such sine wave?




                The pitch and tempo will change in proportion to the speed change. At 33 RPM it would already be musically flat as the correct speed is 331/3 RPM. A 1 kHz test tone - common on test records - would, at 33 RPM, give off $ frac {33}{33.33} text {kHz} $.



                The sinewave would remain a sinewave but stretched in time and, therefore, a lower pitch.







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited 19 mins ago









                K H

                2,360215




                2,360215










                answered 51 mins ago









                TransistorTransistor

                88.2k785189




                88.2k785189

























                    2












                    $begingroup$

                    Changing the speed of the platter simply affects how fast the groove is moving under the needle, nothing else.



                    A sine wave with the time axis compressed or expanded is still a sine wave. In fact, since the groove is a direct mechanical representation of the original complex waveform, you still get the same waveform simply compressed or expanded in time.






                    share|improve this answer









                    $endgroup$













                    • $begingroup$
                      Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
                      $endgroup$
                      – Gabriel Santos
                      56 mins ago










                    • $begingroup$
                      It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
                      $endgroup$
                      – Dave Tweed♦
                      55 mins ago
















                    2












                    $begingroup$

                    Changing the speed of the platter simply affects how fast the groove is moving under the needle, nothing else.



                    A sine wave with the time axis compressed or expanded is still a sine wave. In fact, since the groove is a direct mechanical representation of the original complex waveform, you still get the same waveform simply compressed or expanded in time.






                    share|improve this answer









                    $endgroup$













                    • $begingroup$
                      Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
                      $endgroup$
                      – Gabriel Santos
                      56 mins ago










                    • $begingroup$
                      It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
                      $endgroup$
                      – Dave Tweed♦
                      55 mins ago














                    2












                    2








                    2





                    $begingroup$

                    Changing the speed of the platter simply affects how fast the groove is moving under the needle, nothing else.



                    A sine wave with the time axis compressed or expanded is still a sine wave. In fact, since the groove is a direct mechanical representation of the original complex waveform, you still get the same waveform simply compressed or expanded in time.






                    share|improve this answer









                    $endgroup$



                    Changing the speed of the platter simply affects how fast the groove is moving under the needle, nothing else.



                    A sine wave with the time axis compressed or expanded is still a sine wave. In fact, since the groove is a direct mechanical representation of the original complex waveform, you still get the same waveform simply compressed or expanded in time.







                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered 1 hour ago









                    Dave Tweed♦Dave Tweed

                    123k9152266




                    123k9152266












                    • $begingroup$
                      Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
                      $endgroup$
                      – Gabriel Santos
                      56 mins ago










                    • $begingroup$
                      It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
                      $endgroup$
                      – Dave Tweed♦
                      55 mins ago


















                    • $begingroup$
                      Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
                      $endgroup$
                      – Gabriel Santos
                      56 mins ago










                    • $begingroup$
                      It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
                      $endgroup$
                      – Dave Tweed♦
                      55 mins ago
















                    $begingroup$
                    Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
                    $endgroup$
                    – Gabriel Santos
                    56 mins ago




                    $begingroup$
                    Right, agreed, in the ideal case a a sine wave of same amplitude, but with a diferent frequency, right? The point is for a sin(wt), how the change of rotation speed will affect the frequency?
                    $endgroup$
                    – Gabriel Santos
                    56 mins ago












                    $begingroup$
                    It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
                    $endgroup$
                    – Dave Tweed♦
                    55 mins ago




                    $begingroup$
                    It's linear -- double the speed means double the frequency. That's what compressing the time axis means.
                    $endgroup$
                    – Dave Tweed♦
                    55 mins ago











                    2












                    $begingroup$

                    To really simplify, a record has wiggles in the groove that correspond to the recorded sound pressure. (This ignores stereo, and any compounding, but it answers your question).



                    Events are recorded onto that wiggly grove as they happen -- you can think of the groove as a picture of the sound, with the time domain turned into events happening as the needle follows the groove.



                    If you play the record slower, all the events happen more slowly -- the singer sings slower and deeper, the orchestra does too, etc. Speeding it up does the opposite -- a normal recording, sped up, sounds like a hyperactive chipmunk.






                    share|improve this answer











                    $endgroup$













                    • $begingroup$
                      I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
                      $endgroup$
                      – Toor
                      49 mins ago
















                    2












                    $begingroup$

                    To really simplify, a record has wiggles in the groove that correspond to the recorded sound pressure. (This ignores stereo, and any compounding, but it answers your question).



                    Events are recorded onto that wiggly grove as they happen -- you can think of the groove as a picture of the sound, with the time domain turned into events happening as the needle follows the groove.



                    If you play the record slower, all the events happen more slowly -- the singer sings slower and deeper, the orchestra does too, etc. Speeding it up does the opposite -- a normal recording, sped up, sounds like a hyperactive chipmunk.






                    share|improve this answer











                    $endgroup$













                    • $begingroup$
                      I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
                      $endgroup$
                      – Toor
                      49 mins ago














                    2












                    2








                    2





                    $begingroup$

                    To really simplify, a record has wiggles in the groove that correspond to the recorded sound pressure. (This ignores stereo, and any compounding, but it answers your question).



                    Events are recorded onto that wiggly grove as they happen -- you can think of the groove as a picture of the sound, with the time domain turned into events happening as the needle follows the groove.



                    If you play the record slower, all the events happen more slowly -- the singer sings slower and deeper, the orchestra does too, etc. Speeding it up does the opposite -- a normal recording, sped up, sounds like a hyperactive chipmunk.






                    share|improve this answer











                    $endgroup$



                    To really simplify, a record has wiggles in the groove that correspond to the recorded sound pressure. (This ignores stereo, and any compounding, but it answers your question).



                    Events are recorded onto that wiggly grove as they happen -- you can think of the groove as a picture of the sound, with the time domain turned into events happening as the needle follows the groove.



                    If you play the record slower, all the events happen more slowly -- the singer sings slower and deeper, the orchestra does too, etc. Speeding it up does the opposite -- a normal recording, sped up, sounds like a hyperactive chipmunk.







                    share|improve this answer














                    share|improve this answer



                    share|improve this answer








                    edited 17 mins ago









                    K H

                    2,360215




                    2,360215










                    answered 53 mins ago









                    TimWescottTimWescott

                    6,5891416




                    6,5891416












                    • $begingroup$
                      I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
                      $endgroup$
                      – Toor
                      49 mins ago


















                    • $begingroup$
                      I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
                      $endgroup$
                      – Toor
                      49 mins ago
















                    $begingroup$
                    I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
                    $endgroup$
                    – Toor
                    49 mins ago




                    $begingroup$
                    I was surprised when I first learned how records work. It's so analog that it's amazing it works at all.
                    $endgroup$
                    – Toor
                    49 mins ago


















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