How do you properly use the gain/trim knobs?

[hduncan]

I'm new to this scheme (probably because I do most of my work ITB)..

What's the deal with the Gain and Trim knobs? It seems like the trim knob takes the pre from 0-100% while the gain knob steps it up or down in smaller increments. Is this how it works?

In that case, does it make a difference if you have the trim knob low and the gain knob all the way up, versus having the gain all the way down and the trim all the way up? (set so that either config produces equal volume),

Is there a proper way/rule of thumb to "gain stage" these knobs?

[DPLight]

The gain control switch sets the gain of the active amplifying components in the preamp. The trim control is an output attenuater allowing you to fine adjust the output of the preamp if needed. The C84 trim allows only 5 dB or so of attenuation while the N72 will allow you to attenuate all the way to no output. I will normally set the trim fully clockwise and set the gain to the desired level or a step higher then use the trim to back it off a bit. Sometimes on the N72 I'll purposefully set the gain to overdrive the pre a bit then back off to set the level as to not overdrive the ADC. I think the pre's that do allow full attenuation are that way so you can easily use the over driven preamp without external attenuation.

[Todzilla]

We dumbasses look at it this way:

Top knob increases coloration (at least in transformer based preamps). Once proper coloration has been achieved, bottom knob adjusts signal to interface. Some pres require backing off of top knob to help bottom knob achieve a not-too-hot signal.

[Pleasurehead]

Ask a friend to smack a snare drum every second and stick a mic infront of it. Set the gain to 1-3 and adjust the trim so that it's not too hot. Do the same with the gain at 4-6, 7-9, 10-12 and you'll hear what it does