NYANKO PANKOTANKO'S MOSTLY UNIVERSAL MICROPHONE CONFIGURATION GUIDE:
This is the typical baseline configuration that I recommend to new users when first setting up either dynamic or condenser mics, regardless of whether they're USB or XLR:
Put your mic on a boom arm, have it level with your mouth at a 45-degree angle from your mouth, pointing *at* your mouth, no more than 2 inches away. You should be speaking past it rather than directly into it. The closer the mic is to your face, the less gain you need, the clearer you'll sound, and the less chance of room echo getting in between you and your mic. If you have a condenser mic, you can keep it further away due to the sensitivity of the mic. Just know that condenser mics are SUPER sensitive and require highly sound-treated rooms in order to get optimal sound out of them.
In OBS, keep your mic volume channel slider at 100%, and apply the following filters. Your filter order order should be this from top to bottom: Expander -> Compressor -> Limiter. The standard setup I usually recommend for people is this:
Expander:
Threshold -40 dB
Ratio 4.00:1
Output Gain 10 dB
Compressor:
Threshold -30 dB
Output Gain 10 dB
Limiter:
Limit -1.0 dB
Any parameters that are not specifically listed above can be kept default.
Once those are set, adjust the gain on either your USB mic (knob/button or software) or your XLR-to-USB interface until the volume meter in OBS regularly hits the Limiter (-1.0 dB) during typical speaking volume. The Compressor filter will help bring the volume up during quieter speaking and keep it regulated during louder speaking.
Ignore the color coding on the OBS volume meter as you won't actually clip until you hit the top of the bar, which you won't because of the Limiter. It's okay to touch the Limiter during normal speaking, but just make sure that you're not slamming into the Limiter every time, or else your gain is up too high and your vocals are gonna sound like shit because the waveforms are being crushed by the limiter.
For more sensitive condenser microphones that require less gain, you may reduce the output gain in either the Expander/Compressor filters as you see fit. These are typically baseline parameter settings that I have found are optimal for new configurations and may be adjusted to taste accordingly.
DO NOT use a Noise Gate filter. Noise Gate typically has a hard open/close that is noticeable when speaking, especially as it will tend to cut off the first syllable of every sentence. The Expander serves this purpose instead by reducing the volume of quieter sounds further without completely cutting sound off and serves the exact opposite function of a Compressor.
A Noise Suppression filter will degrade the quality of your audio signal. When it removes the noise from your signal, it has to compensate somehow by removing whatever else that noise overlaps with. The more noise it has to filter out, the worse your audio signal will sound. There is no substitute than a properly sound-treated room, and the best thing you can do to ensure the highest-quality audio output is to ensure the highest-quality audio input.
Good Luck, and Happy Yapping~