General unbalanced single-ended microphone input amplifier , no matter how high the index has done , can inhibit the microphone to introduce the common mode interference signal to noise ratio to be limited. Here the use of NE5532 operational amplifiers produced by high-speed balanced input microphone amplifier does not have this disadvantage , a high signal to noise ratio can be done , to meet the professional requirements , and the circuit is simple , easily produced . Balanced input microphone amplifier circuit shown below . Circuit for the three core operational amplifiers , practical as long as the use of two operational amplifiers , but also more an op amp can be used for other purposes it is used , such as for tone control , or should an op-amp input made up of two balanced microphone amplifier . Circuit : From Cannon ( card by ) socket balanced microphone input signal composed by the Rl-R4 and anti- impedance matching network of RF interference into the two were well after the release of same -phase input zoom , R5-R7 decided two op amp Gain (about 34dB). A2 and its peripheral components constitute the balance of unbalanced gain of 0dB signal converter , it sent before the class ended input signals into two- single-ended output signal , and then fed to the system for further processing . As the circuit is symmetrical balanced input amplifier, op amp used must be precise , general-purpose op amps generally do not declare the use o A1, A2 should be high-speed operational amplifier with NE5532 , LT1057 may also be used if conditions such as " fever " Operational amplifier . All resistors are used the error is 1 % of the colored ring of metal film resistors according to , and use digital multimeter screening, matched with the use , to ensure the consistent double-ended signal amplitude . C1-C3 high-frequency tiles available capacitor , C4 CBB capacitors with good quality . Input jack socket with card by .