Method to reduce noise in microphone circuits

A method for reducing noise in a microphone circuit comprising the steps of:

• receiving, by an isolation block, a supply signal from a power supply, the supply signal comprising a positive voltage and a first ground reference,
• wherein the isolation block is between a microphone preamp circuit and a power supply of a computing device;
• isolating a low noise power supply from a noisy power supply to reduce power supply noise present in the supply signal by providing at an output a positive output voltage and a second ground reference of the microphone preamp circuit, the second ground reference being isolated and different from the first ground reference of the power supply to minimize the voltage ripple noise and provide a clean voltage that is applied to the microphone preamp circuit to prevent amplification by the microphone preamp circuit;
• configuring the microphone circuit to receive power from the low noise power supply;
• and
• configuring a digital signal processor block to receive a microphone preamp output signal from the microphone preamp circuit, to convert the microphone preamp output signal to a digital format, and to transmit the digitized microphone preamp output signal to a computer bus on the computing device,
• wherein the computer bus comprises a third ground reference isolated and different from the first ground reference and the second ground reference, and the digital signal processor block is grounded to the third ground reference.

A computer audio card for coupling to a computing device, comprising:

• an auxiliary power socket configured to receive an auxiliary power connector supplying supplemental power from the computing device power supply;
• a microphone preamplifier configured to receive a microphone signal and amplifying it before transmission to an analog to digital converter (ADC);
• an isolation block between the microphone preamplifier and a power supply, the isolation block configured for conditioning the supplemental power by isolating the supplemental power from power delivered to the microphone preamplifier, the isolation block further configured to receive a supply signal comprising a positive voltage and a first ground reference, the isolation block configured to reduce power supply noise present in the supply signal by providing at an output a positive output voltage and second ground reference, the second ground reference of a microphone preamplifer being isolated and different from the first ground reference of the power supply, resulting in an isolated low noise power supply to minimize the voltage ripple noise and provide a clean voltage that is applied to the microphone preamplifer to prevent amplification by the microphone preamplifer;
• and
• a digital signal processing block configured for receiving a digital signal from the ADC, processing the digital signal, the digital signal processing block is further configured to transmit the processed digital signal to a computer bus coupled to the computing device,
• the computer bus comprises a third ground reference isolated and different from the first ground reference and the second ground reference, and
• the digital signal processor block is grounded to the third ground reference.