Abstract:
The digital sound playback device ( 10 ) of the present invention includes a physical interface that closely simulates an analog scratch turntable. The digital sound playback device ( 10 ) includes a motor ( 30 ) that directly drives a hollow spindle ( 36 ). A platter ( 14 ) is connected to the hollow spindle ( 36 ). A center spindle ( 18 ) is routed through the hollow spindle ( 36 ) where the rotational axis of the hollow spindle ( 36 ) is co-axial with the rotational axis of the center spindle ( 18 ). A full-size vinyl LP record ( 16 ) is removably connected to the center spindle ( 18 ). Digital encoders ( 82, 84 ) are used to respectively detect the rotational speed and direction of the platter ( 14 ) and the center spindle ( 18 ) to respectively create a platter and center spindle control signal. The control signals are used by a central control processor ( 100 ) to determine how the digitized audio should be modified. As a result, a digital audio file can be scratched in similar fashion to an analog vinyl record on an analog turntable.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is related to and claims priority from earlier filed provisional patent application Ser. No. 60/501,487, filed Sep. 9, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention relates generally to the playback and manipulation of audio. The present invention particularly relates to audio players that can manipulate audio in real time to provide different types of sound effects.  
         [0003]     Turntables are well known in the prior art for use in the playback of audio, such as music, which are located on vinyl records. Details of the operation of an analog turntable is so well known, that details of the operation thereof need not be discussed herein. By way of background, these prior art turntables include a rotating platter that is driven by a motor either directly or via belts. A spindle is positioned at the axis of platter. A record, having a center hole, is positioned on the platter with the platter spindle routed through the hole. As a result, the vinyl record remains centered on the platter for rotation therewith.  
         [0004]     A tone arm is provided with cartridge on the free end thereof. A needle in the cartridge communicates with grooves located on the vinyl surface of the record. It is well known that passage of the needle through the grooves of the vinyl record creates analog sound waves that are, in turn, electronically communicated through the tone arm for broadcast through a sound system. Typically, the record is played back in a forward direction and at its specified speed, such as 33⅓ rotations per minute. Such “normal” playback results in the recorded audio to played back as originally desired by the creator of the vinyl record.  
         [0005]     However, it is possible that the playback of these prior art analog vinyl records can be manipulated to create unique sound effects. For example, the record can be sped up or slowed down or moved back and forth while the needle remains within the grooves of the vinyl record. This technique of manually altering the playback of vinyl records is known as the musical art form of “scratching” and can be done to any vinyl record, such as a recording of currently popular music.  
         [0006]     In the industry of vinyl record scratching, special equipment has been designed over the years to accommodate this particular style of interactive playback of vinyl records. For example, specialized needles and turntables, with drive systems that are designed for constant back and forth movement of the platter, have been created. Also, slip mats are typically positioned between the vinyl record and the motor-driven platter to facilitate rotation of the record independently of the turntable platter. Different slip mats can be employed with differing levels of friction to suit the needs of the user of the scratch turntable. In view of the foregoing, the key to effective scratching is the physical interaction of the user with the record and the turntable and needle.  
         [0007]     The use of the scratching technique of sound playback using vinyl records has become very popular. However, the sale and popularity of analog vinyl records has significantly dropped over the years as the preferred medium for recording audio, such as music. Instead, the medium of choice is digital audio for the sound quality, ease of storage and playback. For example, digital audio is commonly stored as a digital file. It can be stored on any type of digital storage media, such as optical compact audio discs and magnetic discs, such as hard drives or compact flash media. As a result, turntables are not used to playback music. Instead, digital compact disc players, computers and digital portable media players are now employed for playback.  
         [0008]     While digital music has important advantages over analog vinyl records, there is a significant drawback in that digital audio cannot be scratched because digital audio is not played back on a record turntable like analog music. Thus, there has become a desire to simulate the scratching of digital audio to obtain similar results as scratching analog audio found on vinyl records.  
         [0009]     There have been many attempts in the prior art to perform a scratch effect on a digital audio file. In the prior art, a digital audio file is typically loaded into a memory buffer from a compact disc or other storage medium. A rotating disc is typically employed with a sensor connected thereto to measure the speed and direction of the disc. Data concerning the rotation speed and direction of the disc is received by a digital microprocessor for digital signal processing according to a desired algorithm and system software. For example, if data is received by the microprocessor that the disc is being slowed down to half speed, then the microprocessor will cause the output signal to be slowed down accordingly to match the speed of the controller disc. Similarly, if the controller disc is rotated backwards, the microprocessor will process the digital audio and output it as reversed audio. Details of digital signal processing by a controller disc is well known in the art and need not be discussed in further detail herein.  
         [0010]     In general, digital signal processing of digital audio to achieve scratching sound effects is quite realistic and suitable for performance by disc jockeys and the like. However, such scratch performers also require a physical interface that is as close as possible, both in look, feel and operation, to an analog turntable to provide as close as possible of a scratching performance. Most importantly, the physical interface for digital scratching will result in a scratch performance that most closely simulates an analog scratch performance.  
         [0011]     The physical interface of prior art digital scratching devices do not closely simulate an analog turntable which disc jockeys and other performers are used to. The controller discs of the prior art are typically small circular platters that are merely provided to only generally simulate an actual vinyl record found in a real analog turntable. As a result, the general feel and action of these prior art digital scratching devices are not particularly close to a real analog turntable.  
         [0012]     However, there have been attempts in the prior to close simulate an analog scratch turntable with a digital device. For example, efforts have been made in the prior art to provide a separate “record” and platter which both have their own detectors connected thereto for monitoring of speed and directional. The “record” in these prior art devices is a custom vinyl or plastic disc that is connected to the spindle of the device. For example, these “records” have a special keyed center hole that engages with a specially configured turntable spindle. Also, the size of the disc is typically smaller than a normal LP disc. This custom disc must be used with the digital scratch turntables of the prior art.  
         [0013]     In view of the foregoing, there is a demand for a device that can closely simulate analog scratching of vinyl records not only from a sound output standpoint but also from a physical interface standpoint. There is a particular demand for a digital scratch turntable to virtually indistinguishable from an analog turntable. There is a demand for the interface “record” to be as close as possible to a real vinyl record. There is a demand for such a digital scratch turntable to include a platter that is identical to platters found in analog turntables. There is a further demand for a digital scratch turntable to use a slip mat to more closely simulate analog scratch action. Also, there is a demand for a digital scratch turntable to have the feel of an analog turntable to improve the overall scratch performance and enjoyment of the performer.  
       SUMMARY OF THE INVENTION  
       [0014]     The present invention preserves the advantages of prior art digital scratch turntables. In addition, it provides new advantages not found in currently available turntables and overcomes many disadvantages of such currently available turntables.  
         [0015]     The invention is generally directed to the novel and unique digital scratch turntable. The turntable of the present invention has particular use in the disc jockey music industry in that the turntable can be used to simulate a scratch performance using digital audio instead of an analog turntable using an analog vinyl record.  
         [0016]     The digital turntable of the present invention more closely simulates analog scratching that any prior art playback device. The present invention addresses the foregoing problems associated with the prior art while providing superior performance and reliability.  
         [0017]     The digital sound playback device of the present invention includes a physical interface that closely simulates an analog scratch turntable. The digital sound playback device includes a motor that directly drives a hollow spindle. A center spindle is routed through the hollow spindle where the rotational axis of the hollow spindle is co-axial with the rotational axis of the center spindle. A full-size vinyl LP record is removably connected to the center spindle. Digital encoders are used to respectively detect the rotational speed and direction of the platter and the center spindle to respectively create a platter and center spindle control signal. The control signals are used by a central control processor to determine how the digitized audio should be modified. As a result, a digital audio file can be scratched in similar fashion to an analog vinyl record on an analog turntable.  
         [0018]     It is therefore an object of the present invention to provide a digital sound playback device that can digitally scratch a digital audio file.  
         [0019]     It is an object of the present invention to provide a digital sound playback device that closely simulates the physical interface of an analog turntable.  
         [0020]     It is a further object of the present invention to provide a digital sound playback device that uses a full-size vinyl LP to simulate scratching.  
         [0021]     Another object of the present invention is to provide a digital sound playback device that has a feel and operation that is identical to an analog scratch turntable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The novel features which are characteristic of the present invention are set forth in the appended claims. However, the invention&#39;s preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which:  
         [0023]      FIG. 1  is a front perspective view of the digital playback device of the present invention;  
         [0024]      FIG. 2  is an front exploded perspective view of the platter and vinyl record assembly of the present invention;  
         [0025]      FIG. 3  is a top perspective view of the turntable platter of the player of  FIG. 1 ;  
         [0026]      FIG. 4  is a top perspective view of the turntable platter of  FIG. 3  with scratch slip mat residing thereon;  
         [0027]      FIG. 5  is a close up view of a vinyl record mounted on the center spindle of the present invention;  
         [0028]      FIG. 6  is a top view of the locking cap position on the vinyl record to secure the vinyl record to the center spindle;  
         [0029]      FIG. 7  is a bottom view of the locking cap of  FIG. 6 ;  
         [0030]      FIG. 8  is a side elevational view of the motor assembly of the present invention mounted under the support housing;  
         [0031]      FIG. 9  is a close up side elevational view of the motor assembly of  FIG. 8 ;  
         [0032]      FIG. 10  is a cross-sectional view through the line  10 - 10  of  FIG. 1 ;  
         [0033]      FIG. 11  is a top perspective view of the motor housing emanating upwardly through the support housing;  
         [0034]      FIG. 12  is a bottom perspective view of the turntable platter;  
         [0035]      FIG. 13  is a close up side elevational view of the motor assembly showing the digital encoder for the center spindle;  
         [0036]      FIG. 14  is a close up side elevational view of the motor assembly showing the digital encoder for the turntable platter; and  
         [0037]      FIG. 15  is a close up view of an encode wheel and an optical detector.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0038]     Referring first to  FIG. 1 , a perspective view of the record controlled playback device  10  of the present invention is shown. The device  10  is audio playback machine that, in general, reads a digital audio file from storage and places it into memory for later custom, on-the-fly manipulation by the user to modify the playback thereof for added enjoyment of the audio itself.  
         [0039]     The audio file can be retrieved from any storage medium, such as compact disc (“CD”) or hard drive. For ease of discussion and illustration, the present invention is shown and described in detail in connection with retrieving a digital audio file from a CD, however, it should be understood that the present invention can be used to retrieve a digital audio file for later manipulation from any storage medium, such as a hard drive or removable media, such as flash memory cards. The scope of the present invention is intended to cover any type of the foregoing storage mediums.  
         [0040]     The playback device  10  is an electrical device that is driven by a power source, such as AC power, using a wall outlet, and the like. As will be described below, various electronic components are employed in the device of the present invention. The nature and type of the power supply can be modified to suit the components employed in the playback device.  
         [0041]     Still referring to  FIG. 1 , the playback device  10  of the present invention includes an outer main housing  12  with a turntable platter  14  rotatably mounted thereon. A user control disc  16 , preferably an actual vinyl record, is removably connected to a center spindle  18 , as seen in  FIGS. 2 and 4 . For example, a user&#39;s favorite vinyl record with a decorative central label portion can be used as the circular disc  16 . As will be described in detail below, the speed and direction of platter  14  and the circular disc  16  are independently monitored so that control signals are generate to modification of an audio signal.  
         [0042]     The playback device  10  also includes a number of user controls positioned about the top surface  12   a  of the main housing  12  of device  10 . The nature and layout of the user controls is preferably provided to best suit the needs of a disc jockey. Most importantly, the user controls are provided that provide a playback device that simulates an analog scratch turntable as closely as possible. As can be seen, the appearance of the playback device  10  is virtually identical to a standard analog scratch turntable except that the present invention does not include a tone arm or a needle cartridge.  
         [0043]     The playback device  10  of the present invention includes a build-in optical reader  19 , namely, otherwise known as a compact disc drive. A front loading slot  20  is located in the front of the device for receiving a compact disc  22 . The compact disc player  19  optically reads the digital audio data on the optical disc  22  and outputs digital audio waveform data. Compact disc players  19  are well known in the art and need not be discussed in further detail herein. An eject button  24  is employed for ejecting the compact disc  22  when further use of that disc is no longer needed. Various buttons are provided for complete control of the playback of the selected audio signal. Further details of the user controls will be discussed below in connection with the operation and use of the playback device of the present invention.  
         [0044]     Turning now to  FIG. 2 , an exploded perspective view of the motor drive assembly, generally referred to as  24 , is shown. Further details of the connection of the platter  14  and the circular disc  16 , such as the vinyl record, to the drive assembly  24  will be described in detail in connection with  FIGS. 3-7 .  
         [0045]     In  FIG. 2 , a base plate  26 , which is connected to the main housing  12  shown in  FIG. 1 , is provided with a pass-through aperture  28  for receiving the motor body  32  of a direct drive motor  30  therethrough. The motor  30  includes a motor housing  32  with a annular-shaped magnet  34  affixed to the inner surface thereof. A hollow spindle  36  is affixed to the outer housing  32  of the motor  30 . As a result, the motor housing  32  rotates in unison with hollow spindle  36 . As shown in  FIG. 3 , a plurality of wire coils  38 , mounted on posts  40 , emanate radially outward toward the annular magnet  34  within the motor  30 . The coils  38  are preferably wound from of metal wire, such as copper, as is well known in the art. The posts  40  that support the coils  38  are mounted to a support circuit board  42  which is, in turn, mounted to the base plate  26  which is attached to the main housing  12  of the playback device  10 . When electricity is passed through the coils  38 , the annular magnet  34  and motor housing  32  rotate in unison thereby providing a direct motorized drive for the platter  14 . The hollow spindle  36  is preferably made of metal, such as aluminum, or can be other materials, such as plastic.  
         [0046]     The center  18  spindle is co-axially mounted through the hollow spindle  36  and freely rotates within the hollow spindle  36 . The center spindle  18  is preferably made of metal, such as aluminum, or can be other materials, such as plastic. The activation of the coils  38  only rotates the annular magnet  34  (e.g. metallic) and motor housing  32  connected thereto not the center spindle  18 .  
         [0047]     The motor  30  is preferably high-torque with a power of 4.5 kgf-cm. The motor  30  can operate at 33 RPM or 45 RPM. A direct drive motor  30  is preferred over other types of motors for its reliability and performance. Also, stationary coils  38  are preferred, however, other types of motors, such as ones with a stationary magnet, are also contemplated by the present invention. These motor configurations are considered to be within the scope of the present invention.  
         [0048]      FIG. 2  further generally shows the attachment of the platter  14  to the top surface  32   a  of the motor housing  32  with a slip mat  44  positioned thereon with a circular disc  16  further residing thereon and connected to the freely rotating center spindle  18 . Details of the interconnection of the turntable platter  14  to the motor housing  32  is seen in  FIGS. 4 and 5 . In  FIG. 4 , a perspective view is shown of the motor  30  extending upwardly through the aperture  28  in base plate  26 . As described above, the motor housing  32  rotates within the aperture  28  in the base plate  26  when electricity is passed through the coils  38  in the motor  30 . A number of keying holes  46  are provided on the top  32   a  surface of the motor housing  32  for engaging with the turntable platter  14 , the bottom of which is shown in  FIG. 5 . The bottom of the platter  14 , which is preferably made of aluminum, includes a mounting connection area in the center thereof, generally referred to as  48 . The mounting connection area  48  includes a pair of keying posts  50  that engage with and reside in the keying holes  46  on the top surface  32   a  of the motor housing  32 . A number of contact pads  52  are also provide within the mounting connection area  48  to communicate with the flat top surface  32   a  of the motor housing  32  to ensure that the platter  14  remains level and parallel with the top surface  32   a  of the motor housing  32 . The platter  14  simply rests on the top of the motor housing  32  and is held in place by gravity, as shown in  FIG. 3 . Finger holes  54  are also provided to facilitate handling of the platter  14 .  
         [0049]     As a result of the keying engagement of the platter  14  to the motor housing  32 , electrical activation of the coils  38  in the motor  30  will effectively rotate the motor housing  32  and the platter  14  simultaneously. Thus, the platter  14  can be rotated to simulate the rotation of a platter of an analog turntable. However, unlike a prior art analog turntable, the center spindle  18  through the center of the platter  14  rotates independently of the platter  14 . In a prior art platter, the center spindle is simply an upward projection from the platter and, as a result, rotates with the platter.  
         [0050]     Once installed on the motor  30 , the platter  14  is in condition for receipt of a slip mat  44  thereon. As seen in  FIG. 7 , a standard slip mat  44  is placed over the top surface  14   a  of the platter  14 . Scratch slip mats  44  are commonly made of foam or felt and provide the needed combination of slippage and grip of a record relative to the platter that is essential to proper scratching feel. The slip mat  44  includes a center hole  56  that permits the center spindle  18  to emanate upwardly therethrough.  
         [0051]     In accordance with the present invention, the platter  14  and circular disc  16  rotate independently from one another. The platter  14  is connected to the motor  30  which controls the rotation thereof. The rotation of the center spindle  18  is controlled by the user&#39;s on-the-fly manipulation in real time. The interface for accomplishing this is a standard sized vinyl record, generally referred to as a circular disc  16 , as mentioned above. Thus, there is a need to securely affixed the circular disc  16  to the center spindle  18  to ensure that the center spindle  18  rotates whenever the circular disc  16  is rotated.  FIGS. 8-10  illustrated in detail the interconnection of the circular disc  16  to the center spindle  18 . It should be understood that the following interconnection is the preferred method of interconnection but other interconnections may be employed and still be within the scope of the present invention.  
         [0052]     In  FIG. 8 , a circular disc, such as a standard vinyl record is employed. The circular disc  16  includes the standard center hole  58  found in all LP discs. A number of keying structures, such as through-holes  60 , are preferably provided through the label portion  62  of the circular disc  16 . An array of three holes  62  are preferably provided, however, other arrays can be used. For example a single hole  62  may be used. Also, the keying structures can be indents in the surface of the circular disc  16  or projections upwardly from the disc  16 .  
         [0053]     The free end  64  of the center spindle  18  also has a keyed structure. Preferably, the free end  64  of the center spindle  18  is of a double cutaways  66  to result in an transversely elongated tip. However, other structures can be used to key the free end  64  of the center spindle  18 .  
         [0054]     A locking cap  68 , a bottom view thereof shown in  FIG. 9 , is employed to secure the circular disc  16  to the center spindle  18 . The locking cap  68 , preferably made of plastic, includes on its bottom side  68   a  a keyed seat  70  for receiving the spindle  18 , namely, its keyed free end  64 . A pass-through hole  71  is also provided. The keyed seat  70  engages with the free end  64  of the center spindle  18  in complementary fashion. For further keying, an array of three posts  72  are provided on the bottom side  68   a  of the locking cap  68  to respective engage and reside in the three holes  60  through the label portion  62  of the circular disc  16 . The array of through holes  60  and mating posts  72  are preferably offset from one another rather than precisely 120 degrees apart and/or the same distance from the center hole  58  of the circular disc  16  to facilitate the orientation and centering of the locking cap  68  on the holes  60  and free end  64  of the center spindle  18  in seat  70 . A top view of the mating of the locking cap  68  onto the circular disc  16  is shown in  FIG. 10 . Indicia  74  further assists in alignment of the locking cap  68 .  
         [0055]     To secure the locking cap  68  to the center spindle  18  with the circular disc  16  sandwiched therebetween, a threaded fastener  76 , as seen in  FIG. 2 , is secured to the free end  64  of the center spindle  18  via the through-hole  71  in the locking cap  68 . More specifically, the threaded fastener includes a made body  76   a  and a male threaded base  76   b.  The free end  64  of the center spindle  18  includes a female threaded bore  78  to receive the male threaded base  76   b  of the threaded fastener  76 . The threaded fastener  76  is preferably reverse threaded, i.e. left hand threaded, to prevent unscrewing during use of the playback device  10 , namely, rotation of the platter  14 . A washer  80  is also preferably employed to ensure a tight threaded engagement of the threaded fastener  76  and the center spindle  18  and to prevent unscrewing during use of the playback device  10 .  
         [0056]     Further, the threaded fastener  76  is preferably configured to be in the shape of the tip of a spindle of an analog turntable to even further simulate the appearance of the playback device  10  of the present invention as an analog turntable. Thus, the pointed free end  76   c  of the threaded fastener  76  is aesthetic in nature only.  
         [0057]     Thus, the platter  14  is securely attached to the motor housing  32  and the circular disc  16  is securely attached to the center spindle  18 . The speed and direction of the rotation of the platter  14  and the circular disc  16  must be independent measured so that the audio signal can be modified in accordance therewith.  
         [0058]     Referring now to  FIGS. 11-15 , details of the rotation speed and direction of the circular disc  16  and platter  14  are shown. In  FIG. 11 , a side elevational view of the playback device  10  of the present invention is shown with the lower portion of the outer housing  12  removed for ease of discussion. The platter  14  rotates above the upper portion of the main housing  12 . A number of mounting blocks  80  are connected to the base plate  26  through which the motor  30  is mounted.  FIG. 3  illustrates the motor  30  prior to mounting. Referring to both  FIGS. 3 and 11 , the circuit board  42  is affixed to the mounting blocks  80  onto which the coils  38  are attached, as seen in  FIG. 3 . As generally shown in  FIGS. 3 and 11 , a first encoding disc  82  is provided for the center spindle  18  and circular disc  16  connected thereto and a second encoding disc  84  is provided for the hollow spindle  36  and the platter  14  connected thereto. Optical detectors  86 ,  88  are respectively provided for each of the encoding discs  82 ,  84 . Details of the preferred structure of the encoding discs  82 ,  84  are discussed below in connection with  FIGS. 13-15 .  
         [0059]     Referring now to  FIG. 12 , a cross-sectional view through the line  12 - 12  of  FIG. 1  is shown to illustrate the preferred arrangement of components of the present invention. The circular disc  16  is coupled to the center spindle  18  with the assistance of the locking cap  69  attached to the top free end  64  of the center spindle  18 . The bottom free end  90  of the center spindle  18  terminates with a first (lower) encoder disc  82  that is attached thereto by a connector assembly generally referred to as  92 . Thus, when the circular disc  16  rotates due to user manipulation, the center spindle  18  will, in turn rotate, thereby rotating the lower encoder disc  82 .  
         [0060]     The center spindle  18  is routed through the hollow spindle  36  which is connected to the platter  14  via the motor housing  32 . When the coils  38  are electrically activated, the annular magnet  34  and motor housing  32  rotate thereby rotating the hollow spindle  36 . Attached to the hollow spindle is a second (upper) encoder disc. When the hollow spindle  36  rotates, the upper encoder disc  84  rotates as well. The use of a hollow outer spindle  36  and an inner center spindle  18  routed therethrough is preferred but is one of many different types of spindle arrangements that can be employed in accordance with the present invention.  
         [0061]      FIG. 13  shows a close up elevational view of the lower encoder disc  82  that is connected to the center spindle  18  while  FIG. 14  shows a close up elevational view of the upper encoder disc  84  that is connected to the hollow spindle  36  (not seen in  FIG. 14 ).  FIG. 15  is a bottom perspective view of the encoder discs  82 ,  84  to illustrate their configuration. More specifically, an array of slits  94  are preferably provided at the free edges  96  of the encoder discs  82 ,  84 . A pair of optical sensors  96 ,  98  respectively embrace the outer free edges of the lower encoder disc  82  and upper encoder disc  84 . The optical sensors  96 ,  98  each include a optical emitter  96   a,    98   a  one side and an optical detector  96   b,    98   b  on the other side. The positioning of the emitters  96   a,    98   a  relative to the detectors  96   b,    98   b  may be reversed, if desired. Light is directed through the slits  96  and is detected on the opposing side of the respective disc  82 ,  84  by the respective optical sensor  96 ,  98 . The pattern of detected light sensed by the optical detector  96   b,  and can be easily used to determine the speed and direction of the circular disc  16  and the spindle  18  connected thereto. For example, the leading and trailing edges of the slits  96  can be sensed for the purposes of determining direction and speed of the rotation of an encoder disc  82 ,  84 . As seen in  FIG. 16 , an audio stream  98  is routed to a microprocessor  100  as modified in real time by data representing the platter movement  102  and circular disc movement  104  to generate a modified digital audio output stream  106 . The modified stream can be outputted directly to a digital output port (not shown) from the playback device  10  or through an analog output port via digital to analog converters. The sensed values are processed in real time to determine the rotational direction and speed of the center spindle  18  and hollow spindle  36  thereby measuring the rotational speed and direction of the circular disc  16  and platter  14 , respectively. The relative speeds and directions of the platter  14  and the circular disc  16  are processed to modify the audio signal  98  in real time to provide a modified signal  106 .  
         [0062]     Use of digital encoding discs using optical sensors for the determination of speed and direction of rotation are well known in the art and need not be discussed in further detail herein. The encoder discs  82 ,  84  are preferably made of stamped or perforated metal, such as steel or aluminum but could be made of other materials.  
         [0063]     In that connection, there are many different methods for measuring the speed and direction of rotation of the hollow spindle  36  and center spindle  18 . The preferred technique is to employ the encoder discs  82 ,  84  with slits  96  and optical sensors  96 ,  98  for their accuracy and low cost. However, it should be understood that many other techniques for detecting the rotation speed and direction of the spindles  18 ,  36  are contemplated herein and are within the scope of the present invention.  
         [0064]     For operation of the present invention, the playback device  10  is powered up and a compact disc  22  is inserted into the slot  20  in the front of the device  10  and is effectively loaded into the compact disc optical reader  19 . An audio track is selected using the selector knob  108  and display  110  for playback from the optical disc  22 . Alternatively, as discussed above, the playback device  10  of the present invention may include a hard drive or memory disc from which the audio file may be retrieved. Once the audio file is loaded from the appropriate storage source, two PLAY buttons  112  are provided for right and left handed use. Either button  112  can be depressed to start playback of the audio track. At this point, the platter  14  will simultaneously begin to rotate to simulate playback on an analog turntable. Thus, the rotation of the platter  14  indicates that playback is in progress. In this condition, the platter  14  is being driven by the motor  30 .  
         [0065]     During this normal playback, the circular disc  16  is in frictional communication with the platter  14  via the slip mat  44 . There is enough friction therebetween that the circular disc  16  rotates in synchronization with the platter  14 . The speeds and direction of both the circular disc  16  (i.e. vinyl record) and the platter  14  will be detected by their respective optical encoders  82 ,  84  and sensors  96 ,  98  as being equal. Thus, the microprocessor  100  simply plays back the audio signal without modification as outputted by the optical reader  19 . The playback signal is based on speed and direction of both the circular  16  disk and platter  14 .  
         [0066]     For playback of a modified audio signal, such as scratch playing, the speed and/or direction of one or both of the platter  14  and the circular disc  16  are altered by the user of the playback device  10 . For example, both the platter  14  and the circular disc  16  can be slowed down the same amount. The microprocessor  100  uses the information to output the appropriate slowed down audio. In another example, if the platter  14  is moving forward at normal speed and the circular disc  16  is moving reverse at normal speed, then the outputted audio  106  will be the audio signal played in reverse. For scratching, it is possible that the platter  14  is moving forward while the circular disc  16  is being moved back and forth. Scratching, pitch bending and cueing can be easily carried out with the present invention.  
         [0067]     Thus, the optical detectors  82 ,  84  will sense all of the relative movements of the circular disc  16  and the platter  14  to deliver real time signals to the microprocessor  100  to play the audio signal forward and backward according to the actions sensed. This processing can be carried out by software that is in read only memory (ROM), onboard a chip or loaded via removable storage.  
         [0068]     It should be noted that real time microprocessor control of a audio signal based on the input of some type of user controller is well known in the art. Therefore, further details thereof need not be addressed herein.  
         [0069]     The playback device  10  of the present invention includes many operational features to take advantage of the realistic record control of an audio signal. Referring back to  FIG. 1 , the power switch (not shown) is engaged to deliver power to the device  10 . A compact disc  22 , that contains the audio file to be manipulated, is inserted into CD ROM drive  19  via the front-loading slot. The eject button  24  ejects the compact disc  22  from the CD ROM drive  19 . The TRACK/MENU SELECT knob  108  is rotated to select tracks. Depressing it selects is for playback. The PLAY/PAUSE  112  buttons starts and stops playback and the platter  14 . Pressing buttons  112  toggles between PLAY and PAUSE of the platter. Each time a PLAY button  112  is pressed after PAUSE, a new cue point is set. A brake adjust wheel  114  is also provided to change the amount of time it takes to stop the platter  14 . A startup adjust wheel  116  is also provided. A CUE button  118  returns and pauses the audio at the last set cue point. A STUTTER button  120  starts the audio from either the first set cue point or the last point of pause.  
         [0070]     Various other operations can be carried out by the device. For example, a scratch mode button  122  and a pitch button  124  are provided to further change how the audio reacts to manipulation of the circular disc. A PITCH slider  126  enables the speed of the platter to be custom set from a standard 33 RPM or 45 RPM. A JOG wheel  128  is used to set effects and control pitch. A beat tracker  130  is preferably built into the playback device  10  to further enhance the use thereof. Looping buttons  132  are employed to control the formation and playback of looped portions of audio. For example, a start point and a stop point can be easily set and used with or without beat tracking to play the selected loop in synchronization with the beat. Various effect buttons  134  can be used to further alter the output of the audio changing its sound characteristics and profile.  
         [0071]     The playback device  10  of the present invention can be easily connected to other audio and video equipment by an audio/video set of connectors, generally shown as  136  in  FIG. 12 , on the back of the device. In general, RCA-type connectors for left and right channel are preferably provided as well as a digital output. A relay connector and a remote start connector can also be provided. Input and output ports for Music Instrument Digital Interface (MIDI) are provided for digital interconnection to other MIDI devices. A voltage selector and power plug connector are also preferably provided. Such connectors are well known in the art and are familiar to disc jockeys and audio technicians.  
         [0072]     It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.