whats the difference between input gain and output gain

Input Gain sets the level going into the interface and Output Gain sets the level going out of the interface.

Gain staging is very important to properly record audio, and it's twice as hard when combining digital with analog.

On a mic pre, input gain varies the amount of amplification of the (very low level) microphone. This can vary between 0 and 60 dB or more. The typical idea is to bring the mic level up to 0 VU, which will read at around -18 dBFS on a digital meter. But, a mic pre, or any analog amplifier, will have its best sound somewhere between too low - the noise floor starts to become apparent - and too high - distortion becomes apparent. Hopefully the designer of the mic pre made it work best around 0 VU with plenty of headroom (gain for peaks above the nominal 0 VU so the peaks don't distort).

If that mic pre has an output control, that will allow you to tailor its output to match whatever comes next in the signal path. Sometimes, for example, you want to drive a preamp hard for a certain sound - dial down the output after that, and the next piece of gear will still receive a reasonable signal (and the next thing might not have an input level control or pad to keep it clean after receiving that hot signal). An Analog-to-Digital converter has components that can be overdriven, so the output of the mic pre shouldn't be too high for that, either.

A compressor needs an output level control because you are controlling dynamics - automatically turning down the loud stuff, for example - and you want the compressor to send out a proper signal with this Make-up Gain.

Remember that the input meters in SONAR only show what is being given to them - your recording level is set somewhere before that.

josegon214


so how should i set my preamp?

That can be quirky & different based on your preamp. Your best bet would be to check the manufacturer's documentation or google what other users recommend. On my preamp it's recommended to set the input gain low (-5 on a scale of -10 to +10) and keep the output level high (7 out of 10) for a clean sound.

On the compressor side, the input gain can be used to set the threshold where the comp starts doing its stuff. Set the meter to Gain Reduction and watch it while you slowly raise the input gain (with a signal going through). When you see the needle start to budge, that's your threshold. Crank it up or down based on how much comp you want. The output knob is for bringing it up or down to an acceptable level for your soundcard.

With analog gear, you can do a LOT by tweaking the in/out gain knobs. Find you gear's cleanest setting, then start experimenting from there. In both cases, preamp & comp, I'd say the input gain is the one you gotta watch most.

to expand (pun intended) a little bit, the output on a comp is usually used to bring up the sound to the same precieved level as the input (compression will generally lower the peaks and lower the precieved value).  On the DBX 163 and some other comps this is part of the settings.   The DBX is sofknee and has only a "amount" slider and "level set."  Add compression w/ the amount slider and the set the volume back w/ the level.  It is an interesting way to think of compression.

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