Differential AUDIO Inout circuit

[tjk]

I understand that this device can work down to DC. Do you have a description of the input circuit, or a portion of a schematic showing the input circuits for the device?

[tjk]

This card is advertised as being able to digitize "DC", but the differential inputs clearly are AC coupled and have a 3dB lower cutoff frequency at 20 Hz. This is certainly not "DC". The input for the codec (removing the amplifier card and connecting directly into the R or L inputs) is better, but is also not "DC". I estimate it to be about 0.3Hz. Perhaps there is a configuration for the codec that will allow DC inputs, but the "alsamixer" app does not expose it.

We really need a circuit diagram of the input circuits!