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#21
This is mostly incorrect. The correct way to adjust the gain of these USB microphones is to adjust the slider in the Microphone Properties → Levels tab. In most mics, this adjusts the PGA inside the mic to get best signal-to-noise ratio (which is like a real zoom motor, not a digital zoom) increasing the signal with minimal increase in noise. You always want to adjust the first stage in the signal chain for best SNR, and this slider controls it. If there's a "boost" slider, then you should increase that first, as it's probably earlier in the signal chain.
The only exception is mics that don't expose input gain controls (typically because there's a hardware knob for it). In that case, Windows 7 and later adds a "digital zoom" volume control that goes from -192 dB to +30 dB, which does increase the noise along with the signal, as you said. Unfortunately, this control is visibly indistinguishable from a real gain control.
If your slider goes from -192 dB to +30 dB, then it's probably the noisy digital gain and you should set it to 0 dB (= "do nothing") to get best dynamic range (and use the physical knob on the product to set the gain instead). In Windows 7 this defaults to +30 dB and creates lots of noise. In Windows 8 and 10 it defaults to 0 dB and has a different range.
If your slider has a different range than this, then it's probably controlling the mic's PGA, and adjusting that slider until you have a good level will give you the best dynamic range.
You should always view the level in dB, since this will function the same way from Windows 7 to Windows 10 to OS X to Android to Ubuntu to whatever. The dB level is what the USB protocol actually uses. The percentage Windows shows by default is meaningless, which has caused a lot of confusion since Windows 8 changed the relationship between percent and dB.
Last edited by yui43; 19 Oct 2016 at 14:34.