Yes, its wise to try and leave the trim knobs set. Nature recording
can require adjustments, so grasping what the circuitry is designed
to do can also help.
I simplify it to: "trim" is "trim-only" and "gain" (or "record
level") is amplification. In practice, when you are working with very
loud sounds and want to use an "ideal" middle scale record level
(4-6), use the "trim" knobs to "trim-back" the sound input to get the
desired meter levels. When sounds are generally soft and the dynamic
range is narrow, the effect of "trim" knobs can be removed from the
circuit by turning them fully clock-wise. That's very common for me.
You can tell when this setting is acceptable because you have to turn
the record gain above half-way to get enough signal. As Marc says,
leaving about 12 dB of "headroom" (un-lit record level meter bars)
should accommodate most louder surprises in the field.
Note that it can introduce some mic preamp noise to have your trim
knobs set low and your record level set high, so trim "off" is my
"nail polish" setting until a significantly loud sound field comes
along. Recordists working in louder environments like the tropics may
routinely use some trim. Another common use of the trim knobs is to
use a tiny bit of "trim" on the louder mic when matching the outputs
of a stereo pair. Rob D.
At 8:40 AM -0400 4/18/08, Marc Myers wrote:
>Hi Alex
>Most pro gear has two adjustments per input. It anticipates you
>might have two very different levels of input and might have to hook
>up to many different kinds of gear over time.
>Turn trim all the say down and set the recording level to nominal,
>depending on your system this will be 0 or -12 or just center
>indent. Play a radio or something else where the audio level can be
>kept more or less constant. Now turn the trim up until the audio is
>where you want it. Your trim is now set. You needn't ever touch it
>again at least for that microphone. From now on, use your record
>level as your master control. This will give 12- 16 Db of headroom
>above nominal and plenty of room to turn in down. Folks who use the
>same audio inputs all the time often use a little nail polish or
>other permanent marker to mark the trim level.
>Marc
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