"Kurt Albershardt" wrote in message


I often find that switching my ADI-8DS input gain to a lower setting
gives me a lower noisefloor than cranking the preamp up.

As you know, that means that either the preamp and/or the card's dynamic
range is not constant with changes in gain.

I wonder which device is dominant here. I would guess that its the preamp.

If a gain control is at the output of a device, then its dynamic range does
not change with changes in gain. The noise floor moves up and down along
with changes in output due to changes of the gain control.

If a gain control is at the input of a device, then dynamic range tends to
increase with an increase in gain. IOW the noise floor tends not to move
down with a decrease of the output due to a decrease in the setting of the
gain control.

Your example seems to follow neither rule. This corresponds to a gain
control someplace in the middle of the device, which is a common pattern
with mic preamps.