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Simple question, gain vs fader(or pot)

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Rich Kaelin
Simple question, gain vs fader(or pot)
on Dec 13, 2012 at 4:42:08 pm

I know audio, but only in support of 25 years of video experience. I am not an audio expert, but I am very well aquatinted with much of the audio world. Something happened the other day which confused me a bit. An A1 came over and lowered the gain on a mixer (sound designs 552, but I assume the same should apply for any mixer). They did this because we were getting a lot of background noise. Then they said it was okay to "pot up" to get good level but not to gain up. I had always considered variable gain as sort of a rough level control and the pot or fader as a fine level control. What I inferred from this is that the gain will also make a mic more sensitive to lower noises, which seems a bit illogical, but may be the case. I was still potting up the inputs in order to output the same level, so I would assume any noise would still be there. How does Gain effect mic sensitivity, and in The future should I use the lowest gain possible to get the desired level? Was this a useful adjustment? It seemed that after I still heard just as much background noise, but they seemed happy. They referred to the original setting as too "warm" a term I have only heard used in recording studios to refer to instrument tone. Could someone clarify the relation between gain, mic sensitivity, and output level. Thanks.

Rich Kaelin
Kaelin Motion Production Services
http://kaelinmotion.com
New York


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Jordan Wolf
Re: Simple question, gain vs fader(or pot)
on Dec 13, 2012 at 8:35:18 pm

"...I had always considered variable gain as sort of a rough level control and the pot or fader as a fine level control."

The gain knob/pot controls how much gain is applied to the incoming signal. It is necessary to boost this level so that it is usable for the mixer's circuitry.

Gain structure is a crucial part of keep the Signal-to-Noise Ratio of a system as low as possible. Every electrical component has some noise that it imparts to the signal passing through it, but a proper S/N ratio setup will keep this to a minimum.

"What I inferred from this is that the gain will also make a mic more sensitive to lower noises, which seems a bit illogical, but may be the case...How does Gain effect mic sensitivity, and in The future should I use the lowest gain possible to get the desired level? Was this a useful adjustment?"

Gain is gain is gain - it doesn't matter where you add it or take it away, if the numbers add up similarly, the end result is the same. Too much analog gain can lead to distortion that, although not usually desirable in our line of work, may be some added harmonics (put more simply: overtones) that "enhance" a signal's timbre/tone.

I work in live sound reinforcement full-time, and proper gain structure is imperative in my setups - I don't want hissing loudspeakers or distorting microphones when one person eats the mic versus the others holding it further away from their mouths.

Depending on your mixer, there may be a different way to "set" your gain level. If you have no way to PFL (listen directly to the head amp) the channel, but there is a "peak" light, I would (1) lower the fader slider or knob/pot and then (2) have the talent speak as loudly into the mic as possible, so that the "peak" light illuminates occasionally. That should get you where you need to be.

Wolf
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Ty Ford
Re: Simple question, gain vs fader(or pot)
on Dec 13, 2012 at 9:56:10 pm

Hello Rich and welcome to the Cow Audio Forum.

"Background Noise" is bad, but to which background was he referring? You are correct that gain is gain.
Each gain stage, trim pot and mic fader, has a center point of operation at which you get the best performance. When you exceed that level, the normal consequence is increased noise.

So having one of the two controls turned WAY UP may bring up system noise, which can loosely be construed as background noise - normally hiss.

" I had always considered variable gain as sort of a rough level control and the pot or fader as a fine level control."

You are entirely correct!

"What I inferred from this is that the gain will also make a mic more sensitive to lower noises, which seems a bit illogical, but may be the case."

You are also correct. This is illogical and does not occur on this planet, e.g. if you're getting a feed from the house that's noisy, turning down the pot to reduce the house noise and expecting it to remain lower while you raise the fader is silly. The damage has been done and you can not unbake that cake.

The general rule of thumb is to do the heavy lifting with the pot but stopping before it llghts the peak or limiter lights so that the fader (at least for the 552, 442, 302) normally rests at 12 o'clock; allowing you to easily turn the fader up and down (within its preferred range) as needed.


Regards,

Ty Ford


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Rich Kaelin
Re: Simple question, gain vs fader(or pot)
on Dec 13, 2012 at 11:01:47 pm

Thanks. The noise being referred to was in the room/building. Creaky chairs, noises from the building at large, people in hall, etc. I was not system hiss (the 522 is incredibly quiet anyway). So lowering the gain on the coarse setting thus causing a need to raise the pot will not eliminate random low noises in the room? I was fairly certain this was the case. Now the reference to "warm" I wonder about. The level was fine, and I had set he gain so the the pot was at about 12 o'clock which is what I always do. I did not hear distortion, after it was turned down I needed to ride pot around 3 or 4 o'clock. Could the original higher gain setting have added tones that warmed up the sound that old not be present by potting up to get the same level out of the mic?

Rich Kaelin
Kaelin Motion Production Services
http://kaelinmotion.com
New York


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Ty Ford
Re: Simple question, gain vs fader(or pot)
on Dec 13, 2012 at 11:14:06 pm

"So lowering the gain on the coarse setting thus causing a need to raise the pot will not eliminate random low noises in the room?"

You are CORRECT SIR! (an Ed McMahon reference)

Please advise the person who told you this to turn in their headphones immediately!

"Could the original higher gain setting have added tones that warmed up the sound that old not be present by potting up to get the same level out of the mic?"

Not on this planet with a 552. You were being given bad audio info.

Regards,

Ty Ford
Cow Audio Forum Leader

PS: If the person in question is in authority, smile and say "Thanks, I really appreciate your help."


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Rich Kaelin
Re: Simple question, gain vs fader(or pot)
on Dec 14, 2012 at 3:05:35 am

THANK YOU, THANK YOU, FRAKIN' thank you! I have been doing this a long time, and have forgotten more than many will ever know. This sounded fishy but I wanted to be sure. I used to work in a recording studio (old school, Studer 24 track and all that jazz) and learned a great deal while there, but never heard anything like this. Unfortunately, there is some semi-authority involved, best not to make wave. But thank you, I thought I was going out of my mind there, forgetting basics. Thank you.

Rich Kaelin
Kaelin Motion Production Services
http://kaelinmotion.com
New York


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Ty Ford
Re: Simple question, gain vs fader(or pot)
on Dec 14, 2012 at 3:57:46 am

Rich,

2" Studers rock!

Here's the deal. You gotta pay it forward now and help somebody else. (You probably already have)
Well, you don't have to, but that's how I ride. :)

Thanks for stopping by and hang here any time.

Regards,

Ty Ford
Cow Audio Forum Leader


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Brian Reynolds
Re: Simple question, gain vs fader(or pot)
on Dec 14, 2012 at 12:44:27 pm

While you are correct assuming there should be little or no difference whether you fader up or pot up there is a difference....

If you go through the schematics of SD mixers (I have a 442) so assuming the same or similar with other models, the limiters are post pot but pre fader...
So for News or ENG link / SNG work where you want a 'Hot' signal to improve the s/n of the link path or the editing process... To do this pot up / fader down and gently hit the limiters and use them as compressors.
Doco style the signal doesn't need to be as hot.

For music production this is not what you want as you are after dynamic range, and hitting the limiters early wont give you that, so you would pot down and fader up in that situation.
Any time you need full dynamics try and avoid using the limiters even though the ones on SD mixers are great.

You can do similar with other mixers eg. Shure FP33 drive the inputs a little harder and hit the limiter but back off the master O/P to get the correct mixer O/P level to suit.... similar thing.

The pot / fader balance these days can be quite critical with lower costing digital consoles and the inbuilt dynamics.

It all comes down to knowing your gear, knowing what the next chains in the signal need and how to change what you do to achieve the best results.


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Ty Ford
Re: Simple question, gain vs fader(or pot)
on Dec 14, 2012 at 2:13:09 pm

Brian, (and Rich)

The idea with SD mixers is not to hit the limiters in the first place, but only to use them for unavoidable emergency overages.

Rich, were you banging the limiters?

Regards,

Ty Ford
Cow Audio Forum Leader


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Rich Kaelin
Re: Simple question, gain vs fader(or pot)
on Dec 14, 2012 at 6:19:32 pm

I was not hitting limiters that I am aware of...but the 522 has an adjustable limiter threshold, and I do not know where they set it. I have been told where to keep my level, between -12 and -6 on our recorders, and that goes into yellow on mixer. It sounded identical to me before and after change. I am not sure if A1 even realizes these mixers have adjustable limiter threshold, or has set all mixers to identical threshold, or if all mixers are still at factory default. This is a multi-unit, multi-crew job, as you may have now gathered. I do know that there were dependencies on other gear, for instance different playback units were showing different levels, despite being digital. When I tried to explain that output may be variable and set differently, I was dismissed out-of-hand. I know one of the units can be adjusted to variable output, but the other was a model I was unfamiliar with. I a not going to make waves, I don't think lessons and advice are received well in this environment. I am a very quick study, and love to learn anything new...but some people become very threatened and aggressive when approached with new info. Sad but true. My view is I'll just be better and more valuable next time. FYI, I know about the limiter threshold on the unit because I downloaded and read manual cover to cover. I don't mind being corrected, as long as the lesson is a valid one. Even after over 25 years in the biz, I still welcome it. Things change all the time, and with all the new standards you can never assume you know anything, let alone everything, anymore.

Rich Kaelin
Kaelin Motion Production Services
http://kaelinmotion.com
New York


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Ty Ford
Re: Simple question, gain vs fader(or pot)
on Dec 14, 2012 at 11:35:29 pm

Rich,

You did good. I once had a shooter tell me my level to his camera (peaks at -6 to -10) was waaaay too hot and that "because this was digital" they should be no higher than -20. Peaks at -20!!! I told him I'd set them there but that he would be seriously under recording. He later told me that the earlier part of the recording was distorted. I sent him a copy of my book and suggested that he listen back to the scene in his camera. (I think he was using an analog audio interface and running line level into mic level inputs.)

So you can find people in power all the time who don't know what's going on and try solutions that may have worked once somewhere, but not in the situation you are in.

You the the right thing.

Regards,

Ty Ford
Cow Audio Forum Leader


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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