UMC202HD.
1: Ch 1 Input level about 10 o'clock - Line, no pad, no cable, output max (channel 2 is the same with these conditions)
2: Ch 2 Input level about 10 o'clock - Instrument (premap active), no pad, guitar cable with bass guitar.
3: In-room, UMIK-1
Slight hiss from speakers, well above their usual hiss (JBL LSR 308), heard if close by, not heard at listening position (10 feet).
Some guitar playing on Ch 2. Didn't affect Ch 1.
1125Hz input to USB Ch 1, 1325 Hz input to USB Ch 2. 1 doesn't bleed to 2, but 2 bleeds to 1.
Conclusion: Useful for messing around, not a "high precision" ADC device. Noise floor similar to that of my room, maybe a little lower. Look elsewhere for a good ADC for measurement or recording.
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1125 and 1325 hz -6dB each, in-room, shows (probably) harmonic and intermodulation distortion of JBL LSR 308
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Reference: just audible (to me) level in-room using levels above: