Trim levels

[Roger Sherman]

Just rented a Sony XL-1. I thought Odb meant no filtering, but the sound levels are very low. When I changed to Trim -41db it sounds great. Anyone know what trim on XL-1 means? There are lots of settings and I don't want to compromise the sound quality.

[Richard Crowley]

What is a "Sony XL-1"?

"Trim" typically has nothing to do with filtering. It is a gain setting, and "0dB" quite likely means "no gain".

[Jay Massengill]

Do you mean a Sony EX-1 (or something similar)? The classic XL-1 is a Canon, but it doesn't have a trim control for audio like you describe.
The Sony EX-1 has a trim control like you describe. In that case, you set the trim to match the sound level of the audio device that's feeding the camera, like a microphone for example. Microphones output a relatively low amount of audio signal compared to line-level devices, so the trim control when using a mic connected to the camera needs to be set to receive a similar low level, like -41db.
The trim control comes before the audio recording level control, so it allows the camera to be set for a wide range of sound input levels without distorting from too much signal coming in or not being sensitive enough when quiet mic signals are coming in.

[Roger Sherman]

Yes, it's the EX-1. So setting to -41db doesn't compromise sound quality?
thanks!

[Richard Crowley]

Originally Posted by Roger Sherman

Yes, it's the EX-1. So setting to -41db doesn't compromise sound quality?
thanks!

NOT setting the trim control properly WILL compromise the sound quality.

[Roger Gunkel]

I have never used an EX1, but typically with audiio, 0db would be used as an optimum sound level, so your input trim would be set to match the level of the incoming signal to the equipment, as previously mentioned, and the recording level would be set to show 0db for your optimal signal level. This should should mean that the best signal to noise level has been set for that particular set of circumstances.

Roger

[Josh Bass]

I've always wondered about this. . .how do you know what that setting should be? What's the objective way to set it up?

Say I'm running a mixer into the cam. So I run tone from the mixer (we'll say line out from mixer to line in on cam). How do I know when that trim setting is correct?

Ditto a mic? There has to be some objective way to set that up.

[Steve House]

Originally Posted by Josh Bass

I've always wondered about this. . .how do you know what that setting should be? What's the objective way to set it up?

Say I'm running a mixer into the cam. So I run tone from the mixer (we'll say line out from mixer to line in on cam). How do I know when that trim setting is correct?

Ditto a mic? There has to be some objective way to set that up.

The mixer's output level should be set to unity gain if it's adjustable. The sine wave lineup tone output from the mixer will then be at 0dBVU, its nominal operating level. While looking at the camera's meters you use its input level controls to place the incoming signal at -18 (EBU) or -20 (SMPTE) dBFS and lock 'em off so they can't be moved. Turning off the tone and bringing up the mic gain on the mixer so the mixer meters hover around the 0dB mark on normal speech should result in the camera's meters bouncing somewhere in the -12 to -10 dBFS range, a good compromise between a high enough level for good signal-to-noise performance yet with some wiggle room for overshoot on peaks without danger of clipping. If you're sending the mic straight into the camera without a mixer, adjust the trim and levels while watching the meters so the average level on speech is about -12 to -10 dBFS. You won't ever be able to say "This mic goes at XXX on the knob's scale" because the actual settings are dependent on interactions between the characteristics of the mic, its placement in relation to the sound source, and the qualities of the speaker's voice. You have to watch the meters constantly in order to do it right.

[Josh Bass]

I may have read your response wrong so forgive me if that's the case.

I know how to set up a mixer with a cam, run tone, etc.

What I mean is, on a cam like the EX1 that has a trim level setting in its audio menus, how do you know where that trim level should be set? This setting is usually expressed as "-41db" or something, and is only adjustable to certain increments (41, 57, etc.) rather than being continually adjustable. Was wondering if there was a way to figure out where that should be given a certain input source (mic, mixer, etc.). It seems like that setting is meant to be more "set it and forget it" than something you mess with every time you use the camera, given how it's buried in a menu.

The one idea I had that seemed somewhat sensible (this is assuming a mic direct into camera, for simplicity's sake) was to set the cam's knobs to unity, and adjust that trim setting til you were getting the levels you mentioned above (-12ish) for normal speech. Is that in the neighborhood of correct?

If you answered that and I misread, I apologize.

[Jay Massengill]

Yes Josh, that is how I would set it. And using your knowledge of the device's output level as a starting point for setting the trim. If it's a very insensitive hand-held dynamic mic it will likely be in the -41 to -57 db range. A much hotter mic like an K6/ME66 or an AT4066 will be set higher like in the -30's.
Wireless mic receivers can often be dialed up into the very hot mic or low line level range, so the trim would need to be set accordingly and to fit the loudness of the situation you're working in.
As long as the trim setting is allowing you to set the recording level controls in the middle of their range to achieve your desired response on the meters and you don't hear any distortion from overloading the input or substantial noise from too much gain from a noisy camera preamp, then you're in the correct trim range.

[Josh Bass]

Thanks. I would assume with a video cam one would be using condensers or a mixer and not dynamics most of the time, though I suppose it probably does happen now and again.

[Richard Crowley]

Originally Posted by Josh Bass

Thanks. I would assume with a video cam one would be using condensers or a mixer and not dynamics most of the time, though I suppose it probably does happen now and again.

Don't make this into a condenser vs. dynamic thing. The setting of the gain/trim control has EVERYTHING to do with the LEVEL of the signal coming in, and NOTHING to do with WHAT is producing that signal.

Just as shotgun vs. hyper-cardioid is not entirely an outdoors vs. indoors thing. It is more correctly a near-reflection vs. open-space thing.

A wise quote attributed to Al Einstein says: "Things should made as simple as possible. But not simpler."

[Josh Bass]

Noted.Thanks.

[Bob Grant]

This setting in the EX1 refers to input sensitivity, ideally that value is relative to 0dBm.
The two physical level controls then adjust gain relative to that. Optimally you adjust the input sensitivity so the meters are reading a good level (peaks below the top three bars), with the gains controls at "5". That leaves you with a good margin to make adjustments quickly.

On the EX1 and EX3 it's a good idea to not let the levels go over the upper three bars on the camera's meters as at that point a limiter kicks in. It's not a harsh limiter so I wouldn't sweat over it too much.

[Josh Bass]

Right, so their trim functions like the coarse trim on an SD Mixer?

Didnt know about the limiter! Is it defeatable?