Mic Level or Line Level?

[Eric Toline]

So what you are saying, Eric, is that all is ok if the camera's meter reads well below -20db, even if the "volume" knob on the camera is cranked all the way, and the 411 receiver is at +5 (maximum setting), and when it is clear on the Tx and Rx and mixer that -20bd is what is being sent?

That just seems odd to me.

It seems to me, unless I am wrong, that all line/mic switches in most gear is an attenuation of the signal before being sent through the very same circuitry a mic signal is sent.

How is sending a hot signal into the camera, where it is attenuated and then sent through the pre amp and then boosted further by cranking the volume knob, any better than sending an attenuated signal from the receiver into the camera where it goes straight into the pre amp and the volume knob rests at a normal position?

Robert

What I am saying is that if you have to have the camera level controls wide open to get a -20dbfs reference level going in at line level, you'd be better served to change the input on the camera to mic level and adjust your receivers output accordingly. Why add extra self noise from the camera's audio path by running it wide open?

I ran a test here yesterday with a Senn G2 system into my 442. With the rx set to +12 output into the 442 at line level, I had to have the trim pot almost wide open and the channel fader at the 3 o'clock position to get reasonable level. The

audio sounded somewhat constricted and lifeless.

Switching the rx back to a -12 output level and the input to mic level I could now set the trim to 12 o'clock and the channel fader to unity. The difference in the richness of the sound and the extra room to adjust controls as required was enough to convince me to stay at mic level going into the mixer and the same for cameras when using wireless hops.

Eric

[RPSharman]

What I am saying is that if you have to have the camera level controls wide open to get a -20dbfs reference level going in at line level, you'd be better served to change the input on the camera to mic level and adjust your receivers output accordingly. Why add extra self noise from the camera's audio path by running it wide open?

I ran a test here yesterday with a Senn G2 system into my 442. With the rx set to +12 output into the 442 at line level, I had to have the trim pot almost wide open and the channel fader at the 3 o'clock position to get reasonable level. The

audio sounded somewhat constricted and lifeless.

Switching the rx back to a -12 output level and the input to mic level I could now set the trim to 12 o'clock and the channel fader to unity. The difference in the richness of the sound and the extra room to adjust controls as required was enough to convince me to stay at mic level going into the mixer and the same for cameras when using wireless hops.

Eric

Oh.  I had thought you were with John on this, but your logic and practical experience seems to match mine.  Thanks for clarifying.

John - I do believe that cameras have cheap circuitry (and I am talking about camera hops here), and I do believe that their design is poor and they simply pad the input and send the signal through the same amplification circuitry.  If this is the case, aren't we better of getting improved levels on the camera by going in at mic level?  I'm not talking physics or engineering here, I am talking real world practicality.  And I ALWAYS ALWAYS record separate system.

Robert

[jonathan chiles]

I am all for whatever works in the field and 99% of the time I'm sure only we would know if we had run our recivers at max into a line input or attenuated into a mic input. But all I can say is running the Lectro SR wide open into the Panasonic HDX900 Line inputs did get rid of some nasty grounding issues that I was having last year on a show.

And for those that want to run Lectros at Line level with Panasonic cameras:

On the MIC/AUDIO2 Menu page in the Panasonic P2 Varicam, there are options of 0dB, +4dB and -3dB for Line Input Gain.

JC

[studiomprd]

"   I have always been told ...  "

WHO has been telling you this??

doing your homework for you!

" Call Lectro and then report back to us. "

My guess is that the transmitter input was set for analog and the gain was too

low.

The transmitter is set up for line level signals only. There is no preamp gain

control, only an attenuator. If he had the transmitter input level set for -20, and

delivered a 0 dBu signal to it, the resulting level would be 20 dB below full

modulation.

Since the D4 system can be set up with a digital input and analog output, which

should fully modulate the transmitter input and provide full level signal peaks at

the output of the receiver.

The manual covers this pretty well.

http://www.gnarlywireless.com/lectrosonicsweb/manuals/D4systemMan.pdf

Hopefully you can understand the manual. It is straightforward, but different than a wireless mic transmitter; of course if you were in direct contact with Lectro, there could be some Q+A about settings and connections that probably would help solve the situation pretty quickly.

Now, I already can see the fingers out there typing: 'this is what a discussion group is for';

well, while there are a couple folks who take great pleasure in doing other folks' homework for them, I really think that people will learn stuff better when they do your own homework. and frankly in solving these questions, it is really much more efficient for folks to work directly with the correct, knowledgeable source.  This will also improve your own troubleshooting skills, and yesterday one of our wise fathers said that 80% of movie-making is problem solving.

so, if you would like to discuss the sound quality of the D4 system, let's discuss it, but if you are trying to get it working properly, maybe J2N has the better idea!!

" There is however a camera menu setting which adjusts line input gain and with that gain increased I was able to get reference tone and peaks to the right levels. "

J2N is a big believer in checking the manuals, and the latest updates are usually found at the manufacturers' web sites...

[studiomprd]

"  that all line/mic switches in most gear is an attenuation of the signal before being sent through the very same circuitry a mic signal is sent. "

well many!!

a lot of professional gear has separate inputs (which must be selected)  that do bypass the initial mic-pre stage.

" The question is what to we do with this "odd" signal that is too low for line level but too high for mic level? "

sometimes when encountering this predicament, I'll take my line output and run it through a (switchable) pad to cut it down to a hot mic level (as the device will see it) so that I can operate the lower quality mic-pre with minimal gain! this usually gets me good performance at the best settings for the lower performance components, and thus is the more optimal gain structure through the entire chain. For example, the Lectro RX's provide that very switchable pad on their output: " setting the 411 at -25 in the menu, switching the camera (Sonys) to "mic" and having the camera levels set in the middle seem to yield levels which match the mixer. "

" So in this situation and this gear, is it better to go line in or mic in?  Discuss. "

 I tend to think like this:" I'm just gonna say as long as you give a listen to it and it sounds good, then does it really matter?  I always try to keep it at line level as much as I can, "

there are still some relevant questions I would consider before making my choice if I were in this situation; Crucial is how does it sound, as it is hooked up?? if it sounds bad, I need to make it better..  If I still want to make a comparison, do I have every adapter or cable needed to go either way, or is one choice easier to implement right here, right now?? what are the capabilities of the equipment involved, right here, right now?? (for example pre-amp quality, and actual performance... depending on the exact toys involved, and my immediate resources, I might lean one way or another; if I have the time to make a comparison, I could determine if there is any apparent difference, though sometimes we are really 'splitting hairs' to try to detect any difference, and in that case I would lean toward my usual best practice: I prefer to move analog audio signals around at higher levels, as in any given circumstance, any additional noise encountered on the transmission path will be lower in comparison to the signal -- our old friend s/n ratio!!  Of course insuring that all of my wiring and setting up is done correctly (I may have to refer to manuals, or go online for a pdf or FAQ from the best most accurate source I can address (and it is not the gang on RAMPS...) but at this point I'm into my standard 'troubleshooting mode' even if it for making a comparison.

"  Why add extra self noise from the camera's audio path by running it wide open? " this is in line with what JB and I are saying; this is getting the best gain staging amongst all the different components.

" running the Lectro SR wide open into the Panasonic HDX900 Line inputs did get rid of some nasty grounding issues that I was having last year on a show. " This is a great example of increasing the signal (audio) to noise (ground hums) ratio!!

THUS:condensed version: it depends!!.

" The mic level (RX out) helps me to deal with noisy locations as well as I can leave the tx gain lower and push the rx output in mic level. " I think it is better to set the TX gain for optimum modulation performance (per Lectro's advice) so that I'm not losing s/n over the transmission path; this is a radio "basic", I have learned and applied since my childhood 'ham radio' days!

" recently used a D4 receiver on a panasonic camera  "

" how you handle this workflow. "

I have not used this setup;  If I were going to, I'd want to pretest, and if that was not possible, I would certainly have a plan B !!

and as I earlier noted: JB has the physics down, and Vin's science is also spot on!

this stuff is the way it is... That's why we call it "arts and sciences"...

" What are you referring to with the term  "EQ padding"? "

perhaps: EQ, padding...

" perhaps you could give me some pro's and cons to running a recording system like this at mic level. " I think we have covered this... I personally believe your desire for more rolloff setting is more a matter of style than substance, but that is your subjective decision, and affects your set-ups...

OK, this is discussing...

[RPSharman]

I have called Lectrosonics many time over the years.  I get answers from engineers, not from people who use these receivers in the field.  The theory of gain structure and electronics often differs from the practical application.

I would like a controlled test with some cameras to determine if it's "better" to record a stronger signal on the camera by going in mic level, or "better" to record a lower signal (which will need to be increased later in the NLE system), or if there is no difference at all.

If there is no difference, then my vote is for "louder" dailies or playback to benefit the first listener of dailies, which may be a producer.

Robert

[Eric Toline]

I have called Lectrosonics many time over the years.  I get answers from engineers, not from people who use these receivers in the field.  The theory of gain structure and electronics often differs from the practical application.

I would like a controlled test with some cameras to determine if it's "better" to record a stronger signal on the camera by going in mic level, or "better" to record a lower signal (which will need to be increased later in the NLE system), or if there is no difference at all.

If there is no difference, then my vote is for "louder" dailies or playback to benefit the first listener of dailies, which may be a producer.

Robert

I vote for "louder". Perhaps it's a holdover from my analog 1/4" mixing days of signal over noise.

Eric

[studiomprd]

" I would like a controlled test "

pretty much every model will be different!

we are discussing, and thus include a lot of generalizations.

and believe me, a lot of the Lectro folks get out to the field; they spend a lot of time talking with and visiting customers and users... say, they even conduct field research, and some controlled tests!

" If there is no difference, then my vote is for "louder" "

I'm assuming that by that you mean more fully modulated, which is what you get with optimum gain staging throughout your system.... this also seems to mean you prefer greater s/n ratios.

[pvanstry]

I have read all the post and i think i help out in cleaning up some seriously but understanding of audio gain staging.

1- Let's be really clear, Gain staging is NOT about listening and hearing if you like the sound better ( this is done only after a correct gain staging and only then ).

2- Gain stagin is the FIRST thing a sound specialist should learn about since it is the basis of operating ANY type of audio gear.  Read about it, educate about it.

3- Lab or real life, there is no difference.  People that say that real life is different simply missed a piece of information about the situation they are dealing with and don't understand the theory behind what they are doing and, unfortunatly hide behind habits instead of seeing it like an opportunaty to learn something new.

4- Yamaha sound reinforcement handbook is a good source for understanding how audio flows thru equipment and the laws that regulate it.

Now as for the correct gain staging of wireless system.  There are two distinct use of the wireless system. 

A- Wireless Transmitter set on a person with a lavalier, going into a Wireless receiver hook into a location mixer.

1- Many people, actually the overwhelming majority in my neiborhood, set there transmitters to low.  Meaning that regardless of how loud the person the mic is on speaks, the transmitter is set too low and then ELECTRONICALLY does not operate within the optimum ( as in sounds best at that level, as in tested for quality in controlled environment by serious technician ) operating level that it was designed for.  For a Lectrosonics transmitters, this means two green led ( -20 and -10 ) and occasional red on the -20.  This means that the transmitter will be operating at approximatly -10db from limiting which is not something you want.  Now a note of interest for later, this does mean that the RECEIVER will then never reach full output modulation ( LEVEL ) so simple deduction tell you tht it will never be more then 10 db under max.  Maximum level being +5db on a UCR 411A ( I am relying on what was said earlier in this post ), then simple math says that it will be outputing a maximum of -5db during peak, and will most likely operate around -15db during normal conversation.

2- Receiver END.  Lectrosonics only pads down its output level, it does not amplify it.  So simple deduction tells me that sn ration is better when the output stage is fully open since there is NO electronic present to increase the gain meaning no device to create additional noise when adjusted upward.  So by opening up the output all the way you are NOT adding noise at all.  In fact, by openning it ( should be understood as NOT padding it down ) you will require less gain boosting ( as in electronic amplifier turn up adding noise to your signal thus reducing SN ratio ).  So you then need to set your mixer input to line level, which is tehn operating in a MUCH LESS noisy manner since it is operating at a higher level thus less induction of noise from outside source, gain stage that add noise and MANY MANY OTHER NEGATIVE SOUNDING THINGS.  SO here is where everybody does the mistake ON THIS type of use.  If you send a tone from a UCR 411a at full level and you mixer is set to line level input, when you PFL your input on the mixer, adjust the preamp gain on the mixer for the meter to read 0db on it.  Then when using a transmitter in real life, if you need to DRASTICALLY increase the gain on the mixer ( not a small adjustement of +or- 12db ) then you need to correctly adjust the gain on the Transmitter as it is not set correctly PERIOD.  Now there is only one time that i would set my transmitter gain low on purpose and then run my Receiver in Mic level on the mixer and that would be when there is no way for me to know the level of the person i will mic and that i will have absolutly no access to them after i set the mic.  Even then it needs to be understood that you are breaking the rules of electronics and that  you SN ration will suffer.  Now this explaination is only good for Lectrosonics UCR411A receivers as i have no operating level on the others type of wireless.  And guys, understand once and for all that when the LCD on a unit says +12db it does not mean the there actually +12db measurable at the output since not only is it a question of the actual calibration of the unit, what the MFG means by actual output level ( physical vs adjustment inside software ).  One really big lesson to learn here is that the ACTUAL level of the receiver is DIRECTLY tied to the TRANSMITTER input level.

B- WIRELESS CAMERA HOP.

1- Here is where we break the rule a bit and mainly because of a quirky output level from Lectrosonics.  When operating a wireless camera hop, the last thing you wnt is to hit the transmitter input limiter.  First because you cannot hear when you do ( you are not listening to anything after the mixer output ) and second because it is going to limit your entire feed.  So we need to gain structure differently then the previous example, we DO NOT want to hit the -20 red on the LEctrosonics transmitters at all.  You need to hit -20db green regularly and occasionally hit -10db green.  You DO NOT adjust the output of your mixer, you simply the input adjustment on the transmitter itself.  If you are turning that adjustment really low, then use it in conjunction with a padded cable in bethween your mixer and transmitter.

2- Receiver end on the camera.  Now if you are still reading this post and you have paid attention to what i have said about the receiver ACTUAL OUTPUT LEVEL, you will understand that since we are running the transmitter ( on purpose ) 10 to 15db lower than where it would like to be for actual optimum operation this also means that the receiver will be operating at lower level.  What i mean is that for the same SOFTWARE SETTING of full level on the UCR411A you will be getting 10 to 15db less ACTUAL LEVEL OUTPUT.  So our level just went down 10 to 15db when set at full level.  MAth wise it means that if you are sending a tone at 0db from your mixer into a transmitter, the receiver set at full level will then output a level of APPROXIMATLY -20dbu.  THAT EXPLAINS why you need to have the adjustment dial on a Sony EX3 all the way up when the camera is set to receive line level ( +4dbu equalling -20dbfs ).  So we need to cheat this by actually setting the camera ( EX3 ) to Mic level and set the your gain on the camera to about 5.  IT IS BREAKING THE GAIN STAGING RULES but only because the LEctrosonics receiver is not a true line level output and that WE WANT to have some forgiveness on the transmitters gain setting in order to avoid limiting there.

In conclusion, you can only make these decision and findings after you understand how the system are operating.  THEN and ONLY THEN can you make quality judgement on the actual audio you are sending/receiving.  Last but not least NEVER, and i mean NEVER let the editor/post make level adjustment needed because you did not respect the -20dbfs average level rule on a shoot.  At that point you are simply not making your job and SERIOUSLY screwing the SN ratio.

Sorry if i piss people, but we are professional and should know our job.

Pascal

[RPSharman]

Pascal,

Thank you.  I think that sums it all up.  I both agree and understand.

Robert

[vale]

maybe i'm a little off topic, anyway, just yesterday i made up my sound cart for new movie. i set 4 lectro 211 in a rack at full output level, then they go into my AD mixer (line inputs) and then by direct outputs in a Cantar, selecting line inputs level from channels menu. I would ask you if someone here has experienced how to calibrate correctly the Cantar line inputs level: i've sent a tone from the mixer (0 VU) to a Cantar channel and i tried to set it at -20 or -18 but in any case this level matched with mixer metering level. i noticed that it seemed to match with setting my note from mixer at -6 db on the Cantar... but i'm not fully 'teorically' convinced... could i have done something wrong?

an other thing is that i had to operate differently on Cantar attenuators to obtain note level at -6 on circular screen on every channels: 'mic' inputs 1-5, but selected line from input level menu, were set at -24 in rectangular screen and 'line' inputs 1-4 were set at -16 in rectangular screen...

i hope i was clear...

[pvanstry]

Just checked on the SOny EX3 input spec. 

Line level setting is +4.  Line level +4 being nominal on the EX3 meaning that the Lectrosonics max +5 being more like -20 when set the way i said earlier is DEFINITLY not happy.  You need the camera to be at Mic level since the Lectros are not giving you a true line level.  What would be needed is a mic/line level setting of let's say -15 or -20 nominal on the camera and then the Lectrosonics would be happy like a pig in .....

my two cents.

Pascal

[Philip Perkins]

We have been running line level on three of these for the better half of four months now using Lectro SR's.

Yeah me too-line level from Lectro hops to EX3.  We turn the EX3 up, sure, but it sounds fine.  I don't like mic level signals running around the camera, esp when I can't moni them--there could be crap from an onboard monitor, video TX, the camera could end up near something that is emitting RF crap etc...

Philip Perkins

[RPSharman]

I would still bet money that the EX3 attenuates a line level signal down to mic level at the XLR input, and it runs around the camera in exactly the same way a mic level from the receiver would.

Robert

[Eric Toline]

I would still bet money that the EX3 attenuates a line level signal down to mic level at the XLR input, and it runs around the camera in exactly the same way a mic level from the receiver would.

Robert

I'm with Robert on that. It would be interesting to know if anyone can find a camera with real seperate line level inputs.

Eric

[RPSharman]

So....

Today I go to work at Warner Brothers.  For those who are unaware, Warner Brothers requires the use of their gear on TV shows shot on the lot.  The basic package is 411/211 receivers feeding a Cooper 208, recording to a DV824.

The package is prepped by the Warner Brothers production sound shop, and everything is set to their "standard" when it is delivered to the set.

Interestingly, the Lectrosonic receivers were set to -15 on their level adjustment, and the Cooper was set to "mic" input on all the inputs from the receivers.

Robert

[Jeff Wexler]

So....

Today I go to work at Warner Brothers.  For those who are unaware, Warner Brothers requires the use of their gear on TV shows shot on the lot.  The basic package is 411/211 receivers feeding a Cooper 208, recording to a DV824.

The package is prepped by the Warner Brothers production sound shop, and everything is set to their "standard" when it is delivered to the set.

Interestingly, the Lectrosonic receivers were set to -15 on their level adjustment, and the Cooper was set to "mic" input on all the inputs from the receivers.

Robert

The "Warner Bros. way" or the highway...  actually, you won't get all the way to the highway. Warner Bros. has a long history of not getting right for the real world, only right for Warner's World, and I could tell some stories that would make your head hurt. The Warner Bros. way is the main reason I have only done 2 movies for Warner Bros. in 40 years. I might add that BOTH movies were done with my equipment and were STILL big problems for the production. Fortunately I had the production company on my side (they weren't too thrilled with some other things Warners did) but had I not had them on my side I probably would have been fired.

[Philip Perkins]

I would still bet money that the EX3 attenuates a line level signal down to mic level at the XLR input, and it runs around the camera in exactly the same way a mic level from the receiver would.

Robert

You mean inside the camera.  I mean OUTSIDE the camera--the cables between the RX and the inputs.  I've had trouble with those picking up stray RF.  Yes, I know how to wire XLR cables.

Philip Perkins

[RPSharman]

You mean inside the camera.  I mean OUTSIDE the camera--the cables between the RX and the inputs.  I've had trouble with those picking up stray RF.  Yes, I know how to wire XLR cables.

Philip Perkins

Aha!!  I see.  This is not something I had thought of, noise between the receiver and the camera, since I have not experienced this.  Something to look out for.

Thanks,

Robert

[whatalob]

I'd like to add my own scenario. usually for my work I use an MS boom mic and a couple of lavs(Audio Technica) on My Nagra VI. On the occasion that I need more channels the only option that I have is to use someone elses Sennheiser G2 lavs. I only have 2 line inputs left though, so I changed the input sensitivity to -6db,and leaving the lavs as is, i.e. as if I had used them for a mic input. It seemed to do the trick. but I still wonder: Is this bad gain staging?

[Mattias Larsen]

I am just getting into lectro and I am trying to wrap my head around how to properly gain stage a 411 (and had similair experiance with a SRB). What Pascal talks about ACTUAL OUTPUT LEVEL is probaby where I fail to connect the dots.

 

If I set the tone to +4dbu on the lectro, I was thinking I adjust the gain on line level to hit -18dbfs or so on a mixpre 6.

 

With this calibration, clipping the TX fully seems to correlate to -12 or so dbfs on the mixpre. Instinctively I would turn up the mixpre gain by another 10-12 db to see the metering properly and have a good idea of when the TX is clipping. Am I on the right track, or can anyone see what I am possibly doing wrong to get optimal performance? After this thread, I guess I should bump the lectro up to +5dbu (athough that should not be a big difference)

[Constantin]

Well, I can’t read through this old thread now, but with Lectros it’s always best to set them at their highest value. It differs from rx to rx, but everything that is not the highest will just be padded down. 
apart from that, gain staging the tx is not always easy, you have to find the best compromise and it can vary from scene to scene, actor to actor, and mic to mic. 
There is a good starting point in the manual

[Mattias Larsen]

How do you gain stage the RX correctly? That is probably my issue more than getting the TX in the right ballpark at the moment.

[John Blankenship]

2 minutes ago, Mattias Larsen said:

How do you gain stage the RX correctly? That is probably my issue more than getting the TX in the right ballpark at the moment.

 

Start with reading what Lectro states about setting the transmitter's gain. 

 

Then... listen!  

 

 

[Mattias Larsen]

15 minutes ago, John Blankenship said:

 

Start with reading what Lectro states about setting the transmitter's gain. 

 

Then... listen!  

 

 

I have read the manual part about the led flashing and tickling the limiter for optimum performance. But I am probably missing something important.