Non Unity Gain in EVAL-ADAU1401EBZ
Using SigmaStudio, I have found that if I route the input directly through to the output, I get attenuation. I have setup a bypass internal to the SigmaDSP to either use the algorithm or bypass it, but if I use an external bypass, there is a large difference in the signals.
Is this inherent to the evaluation board circuit or to the SigmaDSP part itself?
The ADC inputs are actually current-input, not voltage-input, so the relationship between voltage and input level is dependent on the input resistor. In the datasheet, we provide a spec based on an 18 kΩ external input resistor. In this case, you can see that the full scale input is 2 Vrms.
The DAC outputs, however, are voltage-out. Their spec is as follows:
So, you can see that the input is 2 Vrms, and the output is 0.9 Vrms, which is an attenuation of about 6 dB. However, since the inputs are current-referenced, and completely scalable, you could certainly change the resistor value so that the input is also 0.9 Vrms, which would give you 0 dB gain from input to output.
Of course, bypassing in software, as you discussed in your post, is also a viable option.
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Thank you,
EZ Admin
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