Application setup is dual oar singel channel ADC to DAC configuration on an 1701.
Noticed first on single band level detector a remaining, inaudible, noise at -30dB. Investigated further with multiband detector and this noise is in the lowest band. Proceeded to insert "digital silence" via swicth so I could select either external ADC input or tonegenerator. With tone generator selected and "off" the level indicator noise is gone. With ADC input selected and analog side shorted, noise is back level detector.
Also, using external spectrum analyzer on DAC output, the noise is not revealed.