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AD1939 via Electret Mic Preamp Design

Question asked by unh-audio-ee on Jan 14, 2017
Latest reply on Jan 19, 2017 by DaveThib

Hello,

I'm developing an FxLMS accoustic noise cancellation DSP project with the ADSP-21489 EZKit board - its outfitted with an AD1939, and I'm trying to interface electret microphones with the ADC inputs. I'm utilizing John Caldwell's Single-supply, Electret Microphone Pre-amplifier Design, I wanted to check to see if this is a suitable approach, and if a 4-pole sallen-key lowpass filter could be incorporated after the pre-amp stage. On a glance, does the system I've attached look suitable for AD1939 interfacing? Access to the university's laboratory has been limited, and I've been preoccupied with programming the 21489 the past couple weeks. I have a draft model of the proposed Pre-amp/LPF designed in Eagle, but I'd like to confirm/get feedback from the experts before I jump to any conclusions.

 

The RCA to AD1939 connection appears to already have a blocking capacitor, I made sure not to include one on the output of the LPF. A rough-draft image is attached, it operates on a +9V battery, and I have a DC jack with a protection diode incorporated as well. The link below is for the pre-amp design by Mr. Caldwell, and I've attached an image of what I'd like to construct, if the 4-pole LPF can be incorporated.

 

http://www.ti.com/lit/ug/tidu765/tidu765.pdf 

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