Patent Publication Number: US-7711442-B2

Title: Audio signal processor with modular user interface and processing functionality

Description:
BACKGROUND 
   1. Field of the Invention 
   This invention relates to the processing of audio signals generated by musical instruments. In particular, the invention relates to an audio signal processor having its controls and processing functionality being removable from a base audio processing device. 
   2. Description of Related Art 
   Many musical instruments today, including keyboards, electronic drums, and electric stringed instruments, generate their audio output via electronic means. In particular, the electric guitar is comprised of a stringed instrument with magnetic pickups utilized to create an electric voltage that represents the audio signal of the instrument. In order for an electric guitar to be heard at a reasonable level, it is connected to an amplifier and loudspeakers. 
   The tonal properties of an electric guitar are the combined result of the instrument itself, as well as any circuits that exist in its signal path including the amplifier and the loudspeakers used. A musician may select a particular instrument, amplifier, and loudspeakers in order to achieve a specific desired sound. To have further control over the sound, effects processors commonly known as “stomp boxes” can be inserted in the signal path between the electric guitar and the amplifier. 
   Many hundreds of different effect circuits have been created for guitarists to insert into their signal path. These devices typically are housed in a small metal box with a few control knobs on top and a footswitch for turning the effect off and on. The effect that each different unit may generate is predetermined by the circuitry it contains and the controls that are used to adjust the effect&#39;s parameters. 
   When a musician desires to modify the audio signal in a different way than by the stomp boxes he currently is using, another stomp box may be added to the signal chain or may be used to replace an existing stomp box. The sonic range of a given stomp box is determined when it is designed, and other than through physical modification by the user, that designed sonic range is all that can ever be generated. 
   In order to achieve a diverse array of well-known or classic types of guitar tones, a guitarist has traditionally been required to use many different guitars, amplifiers, and effects, including stomp boxes. With regards to the effects, digital signal processing (DSP) techniques have been developed that provide the user with a wider range of tone than previously available with analog effect circuitry. Although multiple devices may still be required for achieving specific sonic results, the available sounds on each effect unit can include digital emulations of many traditionally analog effects. But in these digitally-based systems, their functionality is still limited to the range of sounds designed into the device at the time of manufacture. 
   Most recently, some DSP-based effects have provided a means for updating their firmware via a computer interface such as Universal Serial Bus (USB). In this manner, the range of sound available to the musician can be modified via computer software, allowing the effect unit to be updated with new capabilities in the future. However, these developments do not provide a convenient method of changing an effect unit&#39;s capabilities without a computer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following description of the present invention in which: 
       FIG. 1  is a block diagram illustrating a removable module that may be attached to an audio processing device having embedded digital signal processing capabilities, according to one embodiment of the invention. 
       FIG. 2A  is a perspective view of a housing of an audio processing device, according to one embodiment of the invention. 
       FIG. 2B  is a perspective view of a footpad state selector of the audio processing device that may be actuated by a footpad, according to one embodiment of the invention. 
       FIG. 2C  is a perspective view showing the details of how the footpad is hingedly mounted to the audio processing device housing, according to one embodiment of the invention. 
       FIG. 2D  is a perspective view showing a simplified example of a printed circuit board that may be mounted within the audio processing device, according to one embodiment of the invention. 
       FIG. 2E  is a top view of a fully assembled housing of the audio processing device, according to one embodiment of the invention. 
       FIG. 2F  is a perspective view of a fully assembled housing of the audio processing device, according to one embodiment of the invention. 
       FIG. 2G  is a perspective view of a spring-biased latch, according to one embodiment of the invention. 
       FIG. 3A  is a top view of a removable module that may be inserted into an audio processing device, according to one embodiment of the invention. 
       FIG. 3B  is a perspective view of a removable module that may be inserted into an audio processing device, according to one embodiment of the invention. 
       FIG. 3C  is a side view of a removable module that may be inserted into an audio processing device, according to one embodiment of the invention. 
       FIG. 4  is a perspective view showing the insertion of a removable module into an audio processing device, according to one embodiment of the invention. 
       FIG. 5  is a top view showing a removable module directed to echo effects that is fully inserted and coupled to the audio processing device, according to one embodiment of the invention. 
       FIG. 6  is a top view of another type of removable module directed to chorus effects, according to one embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   In the following description, the various embodiments of the present invention will be described in detail. However, such details are included to facilitate understanding of the invention and to describe exemplary embodiments for implementing the invention. Such details should not be used to limit the invention to the particular embodiments described because other variations and embodiments are possible while staying within the scope of the invention. Furthermore, although numerous details are set forth in order to provide a thorough understanding of the present invention, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present invention. In other instances details such as, well-known methods, types of data, protocols, procedures, components, processes, interfaces, electrical structures, circuits, etc. are not described in detail, or are shown in block diagram form, in order not to obscure the present invention. Furthermore, aspects of the invention will be described in particular embodiments but may be implemented in hardware, software, firmware, middleware, or a combination thereof. 
   Generally, embodiments of the invention relate to an audio signal processor with a removable module that determines the type of audio processing to be performed. More particularly, embodiments of the invention relate to an audio signal processor having a base audio processing device and a removable module that is coupled to the audio processing device, wherein, the removable module determines the type of audio processing to be performed. 
   The audio processing device includes a digital signal processor that modifies an input audio signal in accordance with a signal processing instruction set. The removable module includes the signal processing instruction set, and when the removable module is coupled to the audio processing device, the signal processing instruction set is transferred to and then implemented by the digital signal processor of the audio processing device to perform an audio processing function upon the input audio signal. The removable module may also include a user interface having at least one control to set a control parameter that is transferred to the digital signal processor of the audio processing device to further modify audio processing. 
   In one embodiment, the audio processing device is intended for use with an electric guitar. The analog voltage output of an electric guitar is connected to the audio input of the audio processing device. An analog to digital converter converts the voltage into a digital signal. Further, the digital signal processor (DSP) located within the audio processing device processes the audio signal to create the desired effect for the guitarist. The removable module determines what type of processing the DSP is expected to perform. 
   In some embodiments of the invention, the removable module contains the specific instruction set that the DSP is intended to execute and may also include user controls, such as knobs and switches, to enable the user to modify parameters of the desired audio effect. Movement of these controls is passed from the removable module to the DSP in order for the audio result to be heard. 
   Embodiments of the invention further provide for a user to insert different types of removable modules into the audio processing device in order to provide the user with a wide range of different types of effects. Additionally, the user can exchange modules between multiple audio processing devices arranged in a serial fashion in order to change the order in which the audio signal will be processed. Thus, embodiments of the invention provide a much more affordable and versatile solution to adding audio effects to an electric guitar than in the past. 
   With reference now to  FIG. 1 ,  FIG. 1  shows a block diagram of an audio signal processor  100  having an audio processing device (APD)  102  and a removable module  104 , according to one embodiment of the invention. Embodiments of the invention relate to an audio processing device (APD)  102  having embedded digital signal processing (DSP) capabilities and a removable module  104 . The removable module  104  contains signal processing instructions stored as a signal processing instruction set  129  and a user interface  136 . 
   In one embodiment, the audio processing device  102  and removable module  104  for use therewith, is intended for use with an electric guitar, and hereinafter embodiments of the invention will be discussed with reference to use with an electric guitar. However, it should be appreciated that embodiments of the invention can be utilized with any audio device  101  having an analog or digital audio signal that can be transmitted to the audio processing device  102  for digital signal processing upon the inputted audio signal. Therefore, it should be appreciated that embodiments of the invention can be utilized with any audio device  101  producing an audio signal that can be processed. 
   Looking particularly at the audio processing device  102 , the audio processing device  102  includes an analog to digital converter (A/D converter)  112  coupled to a digital signal processor (DSP)  114 . DSP  114  is further coupled to a memory  116  and a digital to analog (D/A) converter  118 . It should be appreciated that in the case of an input audio device  101  that outputs a digital audio signal, the A/D converter  112  is not required. 
   For example, the analog voltage output of an electric guitar may be connected to the audio input (AUDIO IN  110 ) of the audio processing device  102 . In one example, a standard guitar cable may be inserted into audio input jack  110 . The A/D converter  112  converts the voltage into a digital signal that is inputted into the digital signal processor  114  for digital signal processing. Particularly, digital signal processor  114  processes the digitized audio signal to create a desired guitar effect for the guitarist. 
   A removable module  104  determines what type of processing the digital signal processor  114  is to perform. In one embodiment, the digital signal processor  114  may be a standard digital signal processor produced by Motorola®. It should be appreciated that digital signal processors and the implementation of DSP algorithms to create desired guitar effects or other musical effects is well known in the art. 
   After digital signal processing of the inputted digital signal as played by the guitarist occurs to create the digital effect, then this digitally processed signal is converted back to analog form by digital to analog D/A converter  118 , and the processed analog signal is outputted through audio output  120  to a cable or to other means for transmission to an output device  119  such as an amplifier or speaker for playback. It should be appreciated that if said output device  119  accepts a digital audio signal, then D/A converter  118  is not required. 
   Also, it should be noted that audio processing device  102  may also include additional memory  116  to provide for overflow memory for the DSP  114  in cases where the DSP&#39;s internal memory becomes overloaded. More particularly, memory  116  may be utilized as delay or echo memory in addition to the digital signal processor&#39;s internal memory in order to enhance certain type of effects such as echo and delay. Memory  116  may be a type of Random Access Memory (RAM) such as SRAM, DRAM, etc. 
   The removable module  104  may be removably coupled to the audio processing device  102  by interface  140 . Particularly, a serial interface may be utilized to connect the removable module  104  to the audio processing device  102 . In one embodiment, a serial interface  140  may be utilized such as a 14-pin connector serial interface. In an even more detailed embodiment, the removable module  104  includes a 14-pin male serial connector that mates with a complementary female serial interface of a printed circuit board of the audio processing device  102 . Thus, through the interface  140 , the removable module  104  may be electrically coupled and de-coupled from the audio processing device  102 . 
   Looking particularly at the removable module  104 , the removable module  104  includes particular digital signal processing instructions to create a particular audio guitar effect. These digital signal processing instructions are stored as signal processing instruction set  129  in memory or firmware  130 . This digital signal processing instruction set is coupled and transmitted through serial interface  140  to the digital signal processor  114  of the audio processing device  102  such that the digital signal processor  114  can execute the signal processing instruction set in order to implement the audio effect upon the inputted guitar signal processed through the audio processing device  102 . Memory or firmware  130  may include any suitable type of permanent or writeable type of memory including but not limited to: Read Only Memory (ROM), PROM, EPROM, EEPROM, magnetic or optical disk, etc. 
   In one embodiment, the removable module  104  may include a microcontroller  132  coupled to a user interface  136  and the memory  130 . 
   The user interface  136  may include a number of controls such as knobs and switches to enable a user of the integrated audio signal processor  100 , including audio processing device  102  having a removable module  104  attached therewith, to modify parameters of the audio effect. 
   These control parameters may be passed by microcontroller  132  onto the digital signal processor  114  of the audio processing device  102 . In one embodiment, the microcontroller may be a Philips® microcontroller. The microcontroller  132  may be utilized to pass the signal processing instructions from the removable module  104  to the digital signal processor  114  of the audio processing device  102  through serial interface  140 , as well as the control parameters. Additionally, the microcontroller  132  may be utilized to interpret, modify, or create the signal processing instructions or the control parameters prior to passing them on to the audio processing device  102 . 
   However, in some embodiments, a microcontroller may not be used and the signal processing instructions and control parameters from the user interface  136  may be directly interfaced to the DSP  114  of the audio processing device  102 . 
   It should be appreciated that a user can insert a wide variety of different types of removable modules  104 , each having its own particular effect and associated signal processing instruction set, into the audio processing device  102  in order to alter the type of effect that is expected to be executed by the audio signal processor  100  upon a guitar input signal. Particularly, a wide variety of different removable modules  104  each having a particular effect and a particular user interface may be utilized with the same audio processing device  102 . Thus, a plurality of different removable modules may be purchased by a user and utilized with the same audio processing device providing a wide range of different types of audio effects in a simple and low-cost manner. 
   Examples of these different types of removable modules may include removable modules having signal processing instructions and a user interfaces directed to such well known audio processing effects as: echo, distortion, over-drive, compressor, tremolo, chorus, etc. These and other types of audio effects are well known in the music industry, and particularly as to guitar effects, and the digital signal processing and signal processing instructions to enable these effects, as well as the types of controls and control parameters utilized with these types of effects via user interfaces, are well known to those of skill in this art. 
   However, with embodiments of the present invention, a single base audio processing device  102  having embedded digital signal processing capabilities can be utilized with a wide range of different types of removable modules  104 , each having its own particular type of effect enabled by a specific signal processing instruction set in conjunction with a particular user interface to control effects processing. This provides a low cost and easy system to enable users to obtain a wide variety of different types of effects in a hassle-free manner. 
   Additionally, a user can exchange removable modules between multiple audio processing devices connected to one another in a serial fashion in order to change the order in which the audio effects will be processed. By having a removable module  104 , a much more affordable and versatile solution to adding audio effects to a guitar and other musical instruments is provided. 
   In one embodiment, the audio processing device  102  includes a switch  150  that may have a plurality of different states. For example, the switch  150  may have three states which can be interpreted by the DSP  114  to perform different functions. In the open state  152 , the switch is not depressed. In the half closed state  154 , the switch is depressed partially. In the fully closed state  156 , the switch is pressed all the way down. Typically, the open state  152  would be used to indicate that the switch is not in the half closed state  154  or the fully closed state  156 . 
   Switch  150  may be a typical manual switch on the audio processing device  102  itself that can be manually finger-switched by a user. However, in one embodiment, switch  150  may be a footpad switch in which a user depresses a footpad switch with his or her foot. A particular embodiment of the switch will be discussed in detail later. 
   In the footpad switch embodiment, the fully closed state  156  is usually enabled by the user depressing the footpad fully. In one embodiment, each time switch  150  enters the fully closed state  156 , the DSP audio effect is alternately enabled or disabled. When enabled, digital signal processor  114  applies the digital signal processing effects and user interface controls of the removable module  104  to the audio input signal of the guitar. When disabled, the DSP audio effects are not applied to the audio input signal of the electric guitar. In one embodiment, the DSP audio effects are disabled by routing the audio in signal  110  directly through to audio out  120  via an audio switch  115  controlled by digital signal processor  114 . 
   The footpad switch may also have added resistance in its travel that occurs when it is partially depressed to the half closed state  154  in order for the user to physically distinguish between the half closed state  154  and the fully closed state  156 . The function of the half closed state  154 , as well as the fully closed state  156 , is determined by the signal processing instruction set  129 . These states may be enabled by a double-action footpad switch, as will be discussed. 
   In one embodiment, the amount of time that passes between occurrences of entering the half closed state  154  is used to determine the tempo or speed of a particular DSP audio effect. The half closed state allows the user to tap the footpad at a particular tempo and the outputted effect sound will match that tempo. The changing of tempo via the half closed state may occur whether the DSP audio effect is currently enabled or disabled. 
   Turning now to  FIG. 2A ,  FIG. 2A  is a perspective view of an example of a housing  300  for the audio processing device  102 , according to one embodiment of the invention. As can be seen in  FIG. 2A , the housing  300  of the audio processing device is generally rectangular and oblong in shape and includes a front section  310  for mounting a foot pad switch  304 . 
   The audio processing device housing  300  includes a front section  310  for the mounting and receipt of the footpad switch  304  and a back section  320  for the receipt of the removable module  104 . Within front section  310  of the audio processing device housing  300 , a generally rectangular battery recess area  312  is provided for the receipt of a battery (not shown) that may be utilized to power the audio processing device. 
   Also, adjacent to the battery recess area  312  is a stepped footpad actuation section  314  that mounts a footpad state selector  315  directly under the footpad switch  304 . The footpad switch  304  may be pivoted downwards to activate the footpad state selector  315 . 
   Particularly, the front section  312  of the audio processing device housing includes a U-shaped recessed area  317  about the outer perimeter of the outer portion of the front section  312  of housing  300  in order to accommodate the footpad switch  304 . 
   With brief reference also to  FIG. 2C , the footpad switch  304  may be rotatably mounted into the U-shaped recessed area  317  of the front section  310  of the audio processing device housing  300  by hinge pins  316 . 
   As can be seen in  FIGS. 2A and 2C , the footpad  304  is approximately U-shaped and has two opposed mounting openings  319  for receipt of the mounting hinge pins  316  to rotatably mount the footpad  304  to two opposed rectangular mounting portions  322  of the audio processing device housing  300 . The rectangular mounting portions  322  include rectangular openings  323  complementary to the mounting hinge pins  316  such that when inserted the hinge pins  316  rotatably mount the footpad  304  to the audio processing device housing  300 . Also, the footpad  304  has a rectangular protrusion  328  that mates between the two rectangular mounting portions  322  and has complementary rectangular openings  329  to accommodate the rectangular mounting portions  322  of the audio processing device housing  300 . 
   It should be appreciated that this is only one example of an audio processing device housing  300  and a rotatably mounted footpad  304  and that many other variations are possible. 
   Turning briefly to  FIG. 2B ,  FIG. 2B  is a perspective view of an example of an audio processing device housing  300  that particularly illustrates an example of a footpad state selector  315  that may be mounted within the audio processing device housing  300  for activation by the rotatable footpad  304 . In this example, the footpad state selector  315  is a dual-stage spring actuator for activation by the rotatable footpad switch  304  to thereby create the double-action footpad switch, as previously discussed. The state selector  315  may be mechanically coupled to a footpad switch of a printed circuit board that contains the electronics of the audio processing device  102  as previously discussed with reference to  FIG. 1 . 
   Particularly, with brief reference now also to  FIG. 2D ,  FIG. 2D  provides an example of a printed circuit board (PCB)  350  that may be mounted to the bottom of the audio processing device housing  300 . As shown in  FIG. 2D , the printed circuit board  350  may include a footpad switch  352  that may be activated by the footpad state selector  315 . Based on mechanical input from the dual-stage spring footpad state selector  315  (e.g. a pre-determined amount of force), the footpad switch may change the state of the audio processing device based on the previously discussed switch states: open  152 , half closed  154 , and fully closed  156 . 
   The printed circuit board (PCB)  350  may mount and interconnect the electronic components of the audio processing device  102 , previously discussed, including the A/D converter  112 , the digital signal processor  114 , the memory  116 , and the D/A converter  118 . Further, the PCB  350  may further include a 14-pin serial interface to interface with the matching 14-pin serial interface from the removable module  104 , as previously discussed. 
   Also, the printed circuit board  350  may include stereo audio input jacks  362  for receipt of complementary audio input connectors (e.g. from a guitar cable), as well as stereo audio output jacks  360 , also for receipt of complementary audio output connectors (e.g. from a guitar cable) such that the digitally processed signal can be transmitted to an amplification device. However, typically, at least for guitars, only one input and output jack are utilized since guitars are typically played in mono. Additionally, printed circuit board  350  may include a power supply input  364  for receipt of a direct current power supply to power PCB  350  and the electronics of the application processing device from a wall socket, for example, instead of utilizing a 9-volt or other type of battery. 
   With reference now to  FIGS. 2E and 2F , top and perspective views of a complete audio processing device housing, respectively, are shown. Particularly, these figures show the footpad switch  304  rotatably mounted to the housing  300 , as well as, the printed circuit board with audio inputs  362  and audio outputs  360  mounted to the bottom of the housing. For example, the printed circuit board may be mounted to the bottom of the housing and enclosed with a metal plate (not shown). 
   Also, a rubber pad  370  may be mounted onto the top of the footpad switch  304  to reduce wear and tear on the footpad. 
   The back section  320  of the audio processing device housing  300  includes an approximately rectangular recessed area  380  for receipt of a removable module  104 . As will be discussed, the removable module  104  is also approximately rectangularly-shaped and is sized to fit within the recessed area  380  of the audio processing device housing  300 . 
   With reference also to  FIG. 2G , the audio processing device housing  300  includes a mechanical spring  381  biased latch  382  such that when the complementarily-shaped removable module  104  is inserted into the complementary-shaped rectangular recessed area  380  of the audio processing device housing, it sits flush therein and hook portion  384  of the latch  382  latches onto a complementary approximately triangularly shaped latch portion of the removable module  104  itself to secure the removable module within the recess. The latch  382  includes a button  385  that extends through the back wall  386 , that when pushed in, pivots the removable module back out of the recess of the audio processing device housing. 
   Also, the audio processing device housing  300  along its back wall  386  includes two screw holes  388  in which screws may be inserted through the back wall  386  and into the removable module  104  such that the removable module can be secured therein by screw-type fasteners. 
   Examples of a removable module will now be discussed. With reference to  FIGS. 3A ,  3 B, and  3 C, top and perspective and side views of the removable module  104  are shown, respectively. As can be seen in these figures, the removable module  104  typically includes an approximately rectangularly-shaped housing  390  having a sloped back end  391  and a planar bottom surface  392  including an approximately triangularly shaped latch portion  393  to mate with the hooked portion  384  of the spring-biased latch  382  such that the removable module is fixedly mounted within the recessed portion  380  of the audio processing device housing  300 , as previously discussed; but can easily be removed by simply pushing on the button of the latch  382 . 
   Further, the front portion of the removable module  104  includes a male interface connector  394  to mate with the female interface of the audio processing device  102 . For example, as previously discussed, the serial interface may be a 14-pin serial interface associated with the microcontroller  132  of the removable module for mating with an appropriate interface of the printed circuit board of the audio processing device. 
   Further, the removable module on its top face  395 , may include a user interface  136  that may include a plurality of knobs  396  and switches  397  that enable a user to modify parameters associated with the digital audio effect implemented by the particular digital signal processing instructions of the particular removable module in order to produce the desired audio effect. As previously discussed, movement of these controls, or data created as a result of the movement of these controls, is passed from the removable module  104  to the digital signal processor of the audio processing device through the serial interface. 
   Also, the user interface  136  of the removable module  104  may include a light indicator  398 . In one embodiment, a green flashing light is used to indicate that the digital signal processing effect is on and the light flashes to show modulation speed. If the light is amber colored, this indicates that the digital signal processing effect is off, and likewise it flashes to show modulation speed. However, if the light is red and flashing, it indicates that the battery needs replacing. 
   Turning briefly to  FIG. 4 ,  FIG. 4  is a perspective view showing the removable module  104  being inserted into the audio processing device housing  300 . 
   Turning now to  FIG. 5 ,  FIG. 5  is a top view of an audio processing device  102  having embedded digital signal processing functionality and a removable module having a particular signal processor instruction set and user interface  136  inserted therein. 
   It should be appreciated that a wide variety of different types of removable modules  104  may be inserted into the base audio processing device  102  in order to create a complete functional audio signal processor. This allows a user to insert a wide variety of different types of removable modules into the same base audio processing device  102  in order to alter the type of effect that it is expected to execute. Examples of the different types of removable modules having particular signal processing instruction sets for particular audio processing effects and particular user interfaces associated therewith include removable modules directed to producing: echo effects, distortion effects, overdrive effects, compressor effects, tremolo effects, chorus effects, etc. It should be appreciated that with the embodiments of the invention a wide variety of different types of digital signal processing effects and appropriate user interfaces implementable by a removable module can be inserted into the base audio processing device  102  having an embedded digital signal processor. This provides a very affordable and versatile solution for adding audio effects to a guitar. 
   As particularly shown in  FIG. 5 , in this example, the removable module  104  inserted into the base audio processing device  102  is directed to an echo effect. This removable module is particularly identified as Echo Park™. The audio echo effect more commonly termed “delay” includes a signal processing instruction set to implement a delay effect to an inputted audio signal such as a guitar so that a digitally emulated delay is provided. Signal processing instructions to produce echo and delay effects as stored as a signal processing instruction set of the removable module  104  are well known in the art. 
   Particularly looking at the user interface and controls, the mix knob  502  allows for the blending of the original audio input signal and the delayed signal. The repeat knob  504  controls the amount of feedback of the output of the delay back to the original audio input signal. The time knob  506  controls the amount of time for the delay. The mod knob  508  (or modulation knob) controls the amount of wow and flutter of a simulated tape delay. 
   For example, a switch  512  allows for the selection of tape, digital, and analog. When the switch is switched to the tape mode, the tape mode produces a digital effect to simulate tape echo. The tape echo simulates the effect of a recorded audio signal on a magnetic tape. Particularly, it simulates the sound of a playback head that is physically displaced from the record head and the amount of delay is a function of the space between the record and playback head and the tape speed. When switch  512  is set to digital delay, a very pristine digital delay sound is produced. Conversely, when switch  512  is set to analog, this digitally emulates an analog delay sound that is typically associated with old analog circuit delays. 
   The trail switch  514  enables a trails effect to be on or off. If trails is selected to be on, when the echo or delay effect is turned off, a sound associated with the echo slowly dying off is produced. When the trail switch is turned off, there is no such decay of echoes, the delay just simply ends. 
   Again, the effects associated with the removable module  104  may be turned on or off by the depressible footpad  304 , which may in some embodiments, be a double stage activation switch footpad. Particularly, if the footpad  304  is fully depressed, the effects of the removable module are turned off or on. If the footpad  304  is only slightly depressed, it allows for the tap tempo functions previously discussed. 
   With reference to knob  520 , knob  520  allows a selection of different types of echo or delay. The tap selections produce delays in terms of fractional relationship to speed. Basically, normal means that the tap is set to a quarter note. There are also tap features of eighth note triplets and tap notes in terms of dotted eighth notes. The slap selection provides a very short echo. The swell selection adds a feature where in addition to having echoes a ramp up of volume based on the direct signal is produced. The ducking selection causes the output of the delay to be softer while playing and then the audio output gets louder after the user has stopped playing. The multi-one and multi-two selections provide rhythmic multiple delays that are not evenly spaced. The ping-pong selection selects a delay that goes back and forth between the left and right channel. And, lastly, the reverse selection actually plays the delay backward such that it sounds like the guitar sound is being played backwards. 
   The previously described removable module  104  related to delay or echo is just one of a plurality of different types of removable modules that can be inserted and played with the audio processing device having embedded digital signal processing capabilities. 
   For example, with reference to  FIG. 6 ,  FIG. 6  shows another example of a removable module  104  that contains digital signal processing instructions related to a chorus effect and a user interface  636  directed to allowing the user to modify parameters associated with the chorus effect. Signal processing instructions for chorus effects are well known to those of skill in the art. 
   When the removable module  104  with space chorus effects is inserted into the audio processing device a user playing (for example) a guitar can fully utilize a wide variety of chorus effects. For example, the speed knob  640  adjusts the effect sound from a slow sweep to a speedy warble. The depth knob  642  allows the depth of the chorus to be changed. 
   The color knob  646  relates to the type of chorus selected by chorus switch  650 . For example, when the chorus switch is set to chorus, the color knob allows for a range of vintage analog tones to modern chorus sounds. When the switch  650  is set to tri, the color knob allows a selection of sounds from warm and mellow to shimmering and bright. When the switch  650  is set to vibrato, the color knob functions as a three-way switch for vintage, blue and euro style sounds. 
   Accordingly, embodiments of the invention relate to an audio processing device having embedded digital signal processing capabilities that can be utilized with a removable module that stores particular signal processing instructions for producing a particular audio effect and a particular user interface for the desired effect. This provides an affordable and versatile solution to allow for guitarists to easily add a wide variety of different types of guitar effects in a very simple manner. It should be appreciated that although only two types of effects, echo/delay and chorus, have been discussed in detail, that signal processing instructions and effects for a wide variety of different types of guitar user interfaces can be easily implemented in a removable module and utilized with a base audio processing device having embedded digital signal processing capabilities such that a wide degree of variation is possible. 
   The various aspects of the previously described inventions can be implemented as one or more instructions (e.g. software modules, programs, code segments, etc.) to perform the previously described functions. The instructions which when read and executed by a processor, cause the processor to perform the operations necessary to implement and/or use embodiments of the invention. Generally, the instructions are tangibly embodied in and/or readable from a machine-readable medium, device, or carrier, such as memory, data storage devices, and/or remote devices. The instructions may be loaded from memory, data storage devices, and/or remote devices into memory for use during operations. The instructions can be used to cause a general purpose or special purpose processor, which is programmed with the instructions to perform the steps of the present invention. Alternatively, the features or steps of the present invention may be performed by specific hardware components that contain hard-wired logic for performing the steps, or by any combination of programmed computer components and custom hardware components. 
   While the present invention and its various functional components have been described in particular embodiments, it should be appreciated the embodiments of the present invention can be implemented in hardware, software, firmware, middleware or a combination thereof and utilized in systems, subsystems, components, or sub-components thereof. When implemented in software (e.g. as a software module), the elements of the present invention are the instructions/code segments to perform the necessary tasks. The program or code segments can be stored in a machine readable medium, such as a processor readable medium or a computer program product, or transmitted by a computer data signal embodied in a carrier wave, or a signal modulated by a carrier, over a transmission medium or communication link. The machine-readable medium or processor-readable medium may include any medium that can store or transfer information in a form readable and executable by a machine (e.g. a processor, a computer, etc.). Examples of the machine/processor-readable medium include an electronic circuit, a semiconductor memory device, a ROM, a flash memory, an erasable programmable ROM (EPROM), a floppy diskette, a compact disk CD-ROM, an optical disk, a hard disk, a fiber optic medium, a radio frequency (RF) link, etc. The computer data signal may include any signal that can propagate over a transmission medium such as electronic network channels, optical fibers, air, electromagnetic, RF links, etc. The code segments may be downloaded via computer networks such as the Internet, Intranet, etc. 
   While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, which are apparent to persons skilled in the art to which the invention pertains are deemed to lie within the spirit and scope of the invention.