Audio Banter - View Single Post - Instrumentation op-amp for DC-coupling to audio input?

**Lostgallifreyan**

George Herold wrote in news:a02bdb85-1047-4ba3-aaec-
:

Your band width is maybe
100kHz? (Do you have any filtering before the A-D)

Sorry, I didn't remember to directly answer that... They just have a
differential input stage that adds the two differential signals (doubles)
then quarters the output in the gain of the second of two amps they do this
with, so halving the total signal. After that it goes through a digitally
controlled analog variable resistor (CS3310-KS) followed by a DC blocking
capacitor and then an op-amp stage to make a differential signal for the ADC
(CS5335) with a 2.2nF cap with two 150R resistors to remove anything above a
few hundred KHz.

Apart from using that variable resistor IC they kept it as simple as they
could. Total dynamic range through the system is 98 dB, so only a tad more
than 16 bits worth, but aiming for better in my DC coupler board means I can
adapt other devices reliably.