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The SSM2167 is a complete and flexible solution for conditioning microphone inputs in personal electronics and computer audio systems. It is also excellent...
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SSM2167: Chinese module AGC problem

		
	
				

			

									
					    JMW
					
							

            
            			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jan 20, 2020 
				
			
			
		
    
		
		                     
				
        		
    
		    
		    		    
		    			
    
			    
    I cannot make PCBs for MSOP devices so I bought some modules through Ali Baba. Several suppliers offer the same module. It works correctly with 1:1 compression but not with any other resistor value from Pin 8 to Vcc+ (3 V). It stays in 1:1 mode. For 10:1, I am using 180k. In view of the wide availability of these modules, I wonder if anyone else has made them work or found the problem and cured it. What can I do in the way of probing the module to try to find what is wrong.
    

    

    

     
    
			
    
			
									
		                             
                        

    
    
                                            
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      •  Analog Employees  
      •  Super User  
      
            
						
                            
            
            				
            
                on Jan 20, 2020 12:15 PM
            
            
						
			            		
      
		
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      Hello LMW,
      

      From looking at the picture, R2 is the compression ratio resistor. I would remove it and use an ohm meter to see what the resistance is from pin 8 to +Vcc. It should be close to open. 
      

      Then make sure the far side of R2 is indeed connected to +Vcc. Other than that there should not be much more to it than that? 
      

      Make sure you are putting in a signal that is loud enough to go over the threshold. If you are never reaching the knee point of the compression curve then it would be 1:1. 
      

      So those are my first thoughts. 
      

      Dave T
      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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