Sound card having feedback calibration loop

Abstract

A method of, and apparatus for, limiting inputs to and outputs from a computer sound card forms a feedback connection between the input and output of the sound card amplifier. The voltage of the feedback connection is increased from minimum voltage until an over-saturation condition occurs. This finds the “output voltage limit.” Thereafter, the output voltage of the amplifier is restricted to the output voltage limit. The feedback connection is then terminated and the voltage of the signal being supplied to the amplifier is increased from minimum voltage until the over-saturation condition again occurs. This finds the “input voltage limit.” Thereafter, the input supplied to the amplifier is restricted to the input voltage limit.

1 . A sound card comprising: 
 at least one amplifier having at least one amplifier input and at least one amplifier output;    at least one sound card input connected to said amplifier input;    at least one sound card output connected to said amplifier output;    at least one feedback loop connected to said amplifier input and said amplifier output;    a feedback controller in said feedback loop; and    at least one input voltage controller connected between said sound card input and said amplifier input.    
   
   
       2 . The sound card in  claim 1 , further comprising at least one sound card controller connected to said input voltage controller, said amplifier, and said feedback voltage controller.  
   
   
       3 . The sound card in  claim 2 , wherein said sound card controller is adapted to measure a voltage output limit using said feedback loop.  
   
   
       4 . The sound card in  claim 3 , wherein said sound card controller is adapted to limit the voltage of signals output by said amplifier to said voltage output limit.  
   
   
       5 . The sound card in  claim 3 , wherein said feedback loop is activated only when measuring said voltage output limit.  
   
   
       6 . The sound card in  claim 2 , wherein said sound card controller is adapted to measure a voltage input limit of said amplifier.  
   
   
       7 . The sound card in  claim 6 , wherein said sound card controller is adapted to limit input voltages processed through said input voltage controller to said voltage input limit.  
   
   
       8 . A sound card comprising: 
 at least one amplifier having at least one amplifier input and at least one amplifier output;    a plurality of sound card inputs connected to said amplifier input;    a plurality of sound card outputs connected to said amplifier output;    a plurality of feedback loops, each of feedback loop being connected to a respective pair of said sound card inputs and said sound card outputs;    a feedback controller in each of said feedback loops; and    at least one input voltage controller connected between said sound card inputs and said amplifier input.    
   
   
       9 . The sound card in  claim 8 , further comprising at least one sound card controller connected to said input voltage controller, said amplifier, and said feedback voltage controller.  
   
   
       10 . The sound card in  claim 9 , wherein said sound card controller is adapted to measure a voltage output limit using said feedback loops.  
   
   
       11 . The sound card in  claim 10 , wherein said sound card controller is adapted to limit the voltage of signals output by said amplifier to said voltage output limit.  
   
   
       12 . The sound card in  claim 11 , wherein said feedback loops are activated only when measuring said voltage output limit.  
   
   
       13 . The sound card in  claim 9 , wherein said sound card controller is adapted to measure a voltage input limit of said amplifier.  
   
   
       14 . The sound card in  claim 13 , wherein said sound card controller is adapted to limit input voltages processed through said input voltage controller to said voltage input limit.  
   
   
       15 . A method of limiting inputs to and outputs from a computer sound card, said method comprising: 
 connecting an output of a sound card amplifier to an input of said amplifier using a feedback connection;    supplying a signal having a frequency to said amplifier;    increasing voltage of said feedback connection from minimum voltage until an over-saturation condition occurs where harmonics of said frequency begin being output from said amplifier;    decreasing said voltage of said feedback connection until said harmonics stop being output from said amplifier and recording said voltage as an output voltage limit; and    restricting said output voltage of said amplifier to said output voltage limit.    
   
   
       16 . The method in  claim 15 , further comprising repeating said method to find said output voltage limit with said signal set at different frequency steps.  
   
   
       17 . The method in  claim 16 , further comprising adjusting limits on voltage output from said amplifier depending upon a frequency range of signals being input to said sound card.  
   
   
       18 . The method in  claim 15 , further comprising repeating said method at least one of: 
 when a temperature of said sound card changes more than a predetermined temperature change limit; and    periodically.    
   
   
       19 . The method in  claim 15 , wherein said sound card is used to process audio signals during operational periods, and said method is performed during non-operational periods when audio signals are not being processed; and 
 said feedback connection is used only when finding said output voltage limit and not during said operational periods.    
   
   
       20 . The method in  claim 15 , further comprising maintaining output voltage of said amplifier as close as possible to said output voltage limit by adjusting one of said amplifier and an input voltage controller.  
   
   
       21 . The method in  claim 15 , further comprising, before supplying said signal to said amplifier, adjusting an output voltage of said amplifier to maximum voltage.  
   
   
       22 . A method of limiting inputs to and outputs from a computer sound card, said method comprising: 
 connecting an output of a sound card amplifier to an input of said amplifier using a feedback connection;    adjusting an output voltage of said amplifier to maximum voltage;    supplying a signal having a frequency to said amplifier;    increasing voltage of said feedback connection from minimum voltage until an over-saturation condition occurs where harmonics of said frequency begin being output from said amplifier;    decreasing said voltage of said feedback connection until said harmonics stop being output from said amplifier and recording said voltage as an output voltage limit;    disconnecting said feedback connection;    restricting said output voltage of said amplifier to said output voltage limit;    increasing voltage of said signal being supplied to said amplifier from minimum voltage until said over-saturation condition occurs;    decreasing said voltage of said signal until said harmonics stop being output from said amplifier and recording said voltage as an input voltage limit; and    restricting input supplied to said amplifier to said input voltage limit.    
   
   
       23 . The method in  claim 22 , further comprising repeating said method to find said output voltage limit and said input voltage limit with said signal set at different frequency steps.  
   
   
       24 . The method in  claim 23 , further comprising adjusting limits on voltage being input to and output from said amplifier depending upon a frequency range of signals being input to said sound card.  
   
   
       25 . The method in  claim 22 , further comprising repeating said method at least one of: 
 when a temperature of said sound card changes more than a predetermined temperature change limit; and    periodically.    
   
   
       26 . The method in  claim 22 , wherein said sound card is used to process audio signals during operational periods, and said method is performed during non-operational periods when audio signals are not being processed; and 
 said feedback connection is used only when finding said output voltage limit and not during said operational periods.    
   
   
       27 . The method in  claim 22 , further comprising maintaining output voltage of said amplifier as close as possible to said output voltage limit by adjusting one of said amplifier and an input voltage controller.  
   
   
       28 . The method in  claim 22 , wherein a different frequency signal is used to find said output voltage limit than is used to find said input voltage limit.  
   
   
       29 . The method in  claim 22 , wherein said output voltage limit is higher than input voltage limit.