Sound problem - Distortion on Line in.

[Nick G. Smith]

I have just done 2 jobs on my F3 with different Sound Recordists- We recorded line in from mixer into the F3 and then through SDI into Kipromini. Levels were all correct and no peaking on meters - on the recorded sound both sxs and CF cards we have distortion on the loudest parts.
The distortion is present on the headphones out.

We got round it by recording straight into the Kipro mini which was fine.

I have just tested with a separate mic in to the camera and it is not distorting. I haven't got a mixer here so can't test line in.
The Audio menu settings seem to be correct (Trim set at 41db , limiter OFF, mic AGC HIGH)

I updated to new Firmware 1.4 at beginning of July (?)

Has anyone any clues what may be up. When I have a chance I will get it to Sony Service.

Nick

[John Cummings]

Don't have my F3 in front of me, but is there an option for AGC off?
Edit: Disregard AGC question. Did you mean minus 41dB?.

[Nick G. Smith]

Yes -41db (default setting) my bad. We did play about with the settings but didn't seem to make a difference.
I will try and test the line in again and see what happens.

[Leonard Levy]

Nick, You had a classic impedance mismatch.
I'm not a real soundman but I sometimes have to play one on low budge productions, and know enough to generally stay out of trouble. Anyone is invited to straighten out my language.

First you weren't going into Line-In on the F3 or EX . The trim settings are only active when the inputs are set to "Mic". The numbers will grey out when you switch to Line. Normally the audio from a line level will sound very over-modulated on the mic inputs but -41 is already a slightly low setting for most mics so maybe it was getting closer to the level of line or more likely your line-out was not a fully professional line-out but something in between mic and line. As I understand it consumer equipment often uses levels that are kind of midway between line & mic and this tends to happen with the line-out of a mixer at an event or music show. Not likely from a professional location sound man's mixer though.

Terminology about what's high or low in impedance is weird, and at the risk of being upside-down, I'm going to call -59 higher than -41 because it amplifies the signal more and is expecting a weaker signal ( and mainly because the number is higher). I have had your problem with mics often when the mic trim is set at too high a level for the mic's output. It may look fine on the meters, but loud sounds distort and sometimes it is quite subtle. I had this happen yesterday when a sound guy sent his mixer output to me via wireless and used a mic output from the receiver. ( Not my idea - I don't trust it.) He didn't check the trim and after a quick listen spent his time monitoring his mixer. The meters looked fine, but I noticed that the loud voices were thin and slightly distorted. Lowered the trim and it was fine.

I used to think that as long as the mic level meters looked good when the volume pots were somewhat near the center you had the right trim but it is not always so. Now every time I put a different mic into the camera I check to see what is the optimum trim settings. Some mics like -47 and others -59! Its pretty tricky and you need to stay on top of it especially on a shoot where you don't have a real sound guy running everything through his portable mixer. I've been on one man band shoots where the wireless wants one trim setting , the on camera directional mic wants another and a lav or boom want their own as well - drives me nuts.
With the big mixers at events I have sometimes found their line-out levels ( or impedance ) too low to match my F3 or EX Line-in setting . So I've gone to mic and set the trim as low as -24 which would be way too low for most mics. There is a name for that middling line level but i forget what the sound guys call it - maybe just "consumer line level".

[Leonard Levy]

duplicate post please remove

[Klaas van Urk]

Nick,

your camera uses a limiter to eliminate high peaks in your sound input. That limiter helps most of the time but sends you in to the woods when you're making big mistakes like a setting of -41 dB for a line signal. In this situation the limiter kicks in and does its work as good as possible. But the input signal is still way to high and disorted. And you are misleaded by your meters readout.
First dail your input trims to 5. Switch to line input. Or when the signal is to weak, use mike input at -11 or -17dB at highest. The highest sound level should move the audio meters to 65-70% max. Now make a short sound recording and play it back on your (closed) headphone in a quiet place.
The soundguy can also send you a 1 kHz tone at 0dB. You should dail that to -12 or -6dB on your input level meters. Now if the soundguy does his job fine, everything should be okay.
My recordings are always a bit on the 'soft side'. But its very easy to cranck the sound up by +6 or +12 dB during editing.

[Nick G. Smith]

Thanks for the feedback Leonard.
I'm not a sound recordist so I just let the sound person get on and set everything.

What I find odd is that this has happened only on last 2 shoots - I've been working a lot with my F3 with numerous different sound recordists and previously it has been fine. The last shoot where the distortion happened was with a very experienced sound recordist who I have been shooting a doc with - we did a pick up day and he picked up the distortion problem on the first shot - 2 weeks ago we did 5 days work together and all was fine.
My reasoning is either someone has changed a menu item which we have not picked up ( unlikely as we have gone through the minimal audio settings) or some line in sound 'thingy' has blown. Only other thing I can think that has changed is that I upgraded to new firmware ?

[Leonard Levy]

Non one can troubleshoot your problem without more information but it sound like (forgive the pun) a mistake was made in the settings. I doubt that your camera has gone bad but it does happen.

[Nick G. Smith]

Thanks Klaas, Will try it once I have the chance.

[Leonard Levy]

Klaas, By dialing the trims to +4 or 5 are you effectively changing the mic input into a line input?. I didn't even know you could go that far.

[Klaas van Urk]

Dailing the trims to 5 gives you a good start position. During recording you're able to trim the input up or down when things happen you didn't foresee. Sometimes you have to 'guess' your soundlevel (streetinterviews). Having some room to trim is always desirable. So before setting my input level in the menu I always turn the trims to 5.
B.t.w. the trims are out of use when the inputswitch is switched to 'line'.

[Klaas van Urk]

The line input is fixed at 0dB no matter what you dail in. No preamps used. But often the signal from a mixer or a reciever is to weak. Switching to 'mic' (using a preamp) is necessary to crank up the sound. Minus 11 or -17dB will do.

[Alister Chapman]

While you can trim the sensitivity up and down, there is probably a fundamental difference in the signal paths for the line an mic inputs. I don't know this for sure but I would expect the camera to have a pre-amplifier used when using mic level inputs that amplifies the mic level to line level. When set to line level I would expect this pre-amp to be bypassed. If you don't bypass it and feed it too high a level, like a line level mixer output, it will overload and cause distortion no matter what the trim levels are set to. As Leaonard rightly points out, if you are set to line in, the trim settings are greyed out, so if you were able to adjust or see the trim levels then the input was set to mic in and a line level source would easily over drive this and cause distortion, even if the level meters are showing a decent level.

[John Cummings]

As far as I can tell, the F3 only trims from -20 to -65. While I think it's entirely possible to burn out mic-level preamps by overdriving the inputs in mic level input mode, but you say it now tests clean with a mic at mic level so I doubt that's the issue.

Any experienced soundman with pro gear will almost always use line level inputs and tone out the camera at 0dB, and then test playback AND continue to monitor from the camera or the outboard recorder itself while recording. I suspect sound operator error.

[George Griswold]

Alister is correct... on Betacams you could feed a line in when the camera was set to Mic and dial down the gain to make the meters come in at 0dB, but the pre-amp would overload and the sound would be un-usable/ over-mod. I suspect the F3 would be the same way.