LL4901 is a 200 ohm : 5 k microphone input transformer, winding turns ratio 1+1:10. The LL4901 is discontinued and no data sheet is available. 
For replacements, please study LL1538.


Pin configuration (transformer seen from component side with label readable)    

4,    3,    2,    1

      LL4901      

8,    7,   6,    5        

LL4901 Usage (1:5)  
in+		pin 1  
in-		pin 4  
connect pis 2 + 3  
out+	pin 6  
out-	pin 7  
ground  pin 5