Sensitivity vs Gain

KINOKS

KINOKS

Well-known member
I've been wanting to ask about this for quite some time now... On my Roland R-26 there is a setting called sensitivity. It's a setting that is applied to each input separately. It produces higher volume the higher the setting, but it doesn't seem to raise the noise flour like gain does.
Could somebody please explain what this is?:)

thx
 
The channel input control (call it "sensitivity" or any number of other names) actually controls the GAIN of the microphone input preamp stage. Its primary purpose is to "normalize" sources of various incoming levels so that they are easier to mix together (or to record within the optimal zone). At the same time you are normalizing the input level, you are optimizing the signal-to-noise ratio of that input stage.

All other level (and pan) controls are potentiometers, or user-adjustable voltage-dividers. They allow you to select the proportion of the signal that you let through (to "mix" various sources together, for example). They do NOT affect the gain of the audio stage.

Note that the word '"sensitivity" is also used to indicate the "efficiency" of a microphone or a speaker (or headphones, etc.) The more "sensitive" a microphone is, the less sound pressure level it takes to put out some standard signal voltage (like 1 millivolt). And at the other end of the audio chain, a speaker with higher sensivity puts out more sound-pressure-level for a given power input (such as 1mW).
 
From the R26 user manual, page 44, just for kicks:

How input sensitivity and input level are related

Input sensitivity adjusts the loudness of the input signal being received as the recording source. Input level is an additional fine adjustment applied to the signal after it's been adjusted by input sensitivity, in order to optimize it for recording.

* Adjust the input sensitivity in the following situations

- The kevel meters don't move sufficiently even when the knob is in the maximum position.
- The PEAK indicator lights even when the knob is in the minimum position.
Click to expand...

Interesting that "gain" is not used in Roland's terminology anywhere in the manual.
 
Thx guys.

Richard Crowley said:
Note that the word '"sensitivity" is also used to indicate the "efficiency" of a microphone or a speaker (or headphones, etc.) The more "sensitive" a microphone is, the less sound pressure level it takes to put out some standard signal voltage (like 1 millivolt). And at the other end of the audio chain, a speaker with higher sensivity puts out more sound-pressure-level for a given power input (such as 1mW).
Click to expand...

Okey, so this is why it doesn't really raise the noise floor. And the "gain" knob adjusts the voltage of the signal right? Much like ISO or gain on a camera does?
Is it possible that the sensitivity can be set to high for a certain microphone? For instance on the Octava MK012 if the sensitivity is to high the microphone picks up rumbling noise immediately. It picks up everything, so much so that there is no chance of using it on a boom pole! I first thought the mic was a goner but then figured out the sensitivity was set to high for the mic.
So sensitivity means that the mic is more prone at capturing small noises (smaller sound pressure waves) and stuff that it wouldn't pick up otherwise, right? This would then also mean that sensitivity isn't such a simple setting as gain is.
 
@KINOKS, no, I'm afraid I have not communicated properly. The sensitivity of a microphone or a speaker is "baked in" when the mic/speaker is designed. There is nothing externally you can do to change the sensitivity of a mic or speaker.

You can change the gain of the mic input stage to compensate for low microphone sensitivity (as the Oktava MK012). This is exactly why I think that the gain control on the mic preamp should NOT be named "sensitivity". That is a misnomer and causes the kind of confusion we are seeing here.

Now, the more gain you apply in the mic preamp the more noise you will get along with the mic signal. But all mic preamps are not created equal. Some are much quieter than others. For example, premium equipment like Sound Devices is in the top of the spectrum of great mic preamp performance. OTOH, there are brands with reputations for mediocre-performing mic preamps that are inherently noisy and will not perform well with low-sensitivity mics like Oktava MK012.
 
You probably communicated properly but my "audio" knowledge is lacking and therefore I didn't understand. I do however understand that you can't change the mics signal to noise ration.
So I still don't understand the difference between the "sensitivity" setting and the gain knob:) As in the case of MK012 if you turn up the gain knob there are no issues with the microphone but if you turn up the sensitivity the mic gets unusable.
If I understand you correctly both things are gain but they amplify the signal at different stages? One amplifies the preamp inside the mic and the other inside the recorder? Khm...I didn't know that mics had preamps in them:)
 
I guess I can't really have this discussion about a "sensitivity control" because that is a myth. Whatever knob that is does NOT control "sensitivity". Sensitivity, in the traditional definition of the word cannot be changed. We can only compensate for various microphone sensitivity by adjusting the gain of the mic preamp. Continuing to call that gain adjustment by the name "sensitivity" will continue to cause confusion.

So the very question "the difference between sensitivity setting and gain control" is incomprehensible to me. Or perhaps I can answer the question by saying that a "sensitivity control" is a myth like a unicorn. On equipment in the Real World there are controls for adjusting the gain of a mic preamp, and then there are "volume" or "level" or "mix" or "pan" controls that adjust the audio level further along the chain.

Now, if you want to drop the term "sensitivity control" and use the more proper term "gain adjustment" or "gain control", then I can understand what we are talking about.

Repeating, I believe the confusion here is the use of the term "sensitivity control". If you eliminate that from your vocabulary, audio will probably be easier to understand.
 
The Roland R-26 manual says:

How input sensitivity and input level are related
Input sensitivity adjusts the loudness of the input signal being received as therecording source. Input level is an additional fine adjustment applied to the signalafter it’s been adjusted by input sensitivity, in order to optimize it for recording.
Click to expand...

The gain of the input stage of the recorder audio chain can be adjusted using the mis-named "sensitivity" adjustment. This must be optimized for whatever signal level you are trying to record. Whether it is a very low-sensitivity microphone used too far away, or whether it is a very "hot" +22dB line level signal from some piece of pro gear.

"Optimized" means pretty much the same thing at EACH AND EVERY point along the audio chain. Your job is to set each adjustment along the chain to keep your audio signal in the "Goldilocks Zone" (Not too HOT, and not to COLD). "Hot" means that the loud peaks of the audio are getting clipped because digital audio has a very precisely defined upper limit. If you go the slightest bit over that level (0dB FS = Full Scale) then your audio signal will have the peaks clipped off flat. And the audio will sound distorted, perhaps only mildly, but possibly beyond repair and beyond ineligibility. And conversely, "cold" means that the signal is too low and is wallowing around "down in the mud" of the noise of the various parts of the system (including acoustically through the air).

The first stage of the audio chain (typically the mic preamp) is the MOST CRITICAL point in the entire chain. If you get it wrong there, no amount of fiddling with the settings downstream will be able to "fix" the problems. So, setting the input gain (which Roland mis-names "Sensitivity") is your first order of business. Once you have that set properly, then you can use the front-panel knobs to adjust the recording levels. But, as the Roland manual says, if the signals are too high even at low settings of the record level controls, then you have the gain ("sensitivity") set too high. And conversely, if the signals are too low, even at high setings of the record level controls, then the gain ("sensitivity") is set too low.

Your perception that "gain raises the noise floor but sensitivity does't) is incorrect. That perception appears to be based on a too-low setting of the "sensitivity" control. Reality is rather more complex than that. This is the whole concept of "gain staging". There is probably a YouTube tutorial video on the subject somewhere.
 
Yeah, I probably didn't notice the noise floor being raised - you sir are probably correct - but the gain knob definetelly raises it more than "sensitivity" does. I never really attended much attention to it (I'm not the one using the recorder mostly) but I do however use it time to time for simple shoots.
Okey the sensitivity is actually input gain but what is "gain" then? Do keep in mind that "sensitivity" (I feel stupid say sensitivity now but this is what Roland wrote so I'll keep saying that as not to confuse) is a menu option. It is not a quick access operation that can be accessed by knobs or buttons and I think it can't be set while recording. The main thing is the big gain knob on the front of the recorder.
So what is the gain knob?

Is this gain knob maybe, just maybe, digital and the "sensitivity" is the true analogue ie. normal gain? This would explain why "sensitivity" actually effects the mic performance (the Oktava example I gave before) and the gain knob doesn't and why the gain knob has a higher effect on the noise floor. If this is true than this is sh*t, as the real control is hidden from easy access and the one you really want to use in post and not while shooting is in the front!
 
I assume that when you say "gain knob" you mean the two big physical knobs on the top panel labled "Input 1" and "Input 2"?

No it is DEFINITELY NOT the case that the gain knob raises the noise floor more than "sensitivity" does. If that is what you are hearing, then it is almost certainly the case that the input gain (which Roland calls "sensitivity") is adjusted TOO LOW.

Remember that first stage gain affects EVERYTHING downstream. Downstream adjustments DO NOT affect the signal-to-noise ratio, they only reveal more or less of what was established back at the first stage.

"Gain" is simply a multiplication factor. A gain of zero means that nothing gets through. It is turned all the way off. Just as any number multiplied by zero = zero. A gain of 1 means that the same level comes out as what came in. Any number multiplied by 1 = the same number.

A "gain" of something less than 1 is called "attenuation". That is what the "Input 1" and "input 2" knobs do. They are user-controlled variable resistor voltage-dividers that take some fractional portion of the total available signal.

When you start multiplying the signal by numbers > 1 then you are increasing, or boosting, or multiplying the signal. It would not be uncommon to see a microphone input stage have gains up to 1000 (40 dB)
 
Richard Crowley said:
I assume that when you say "gain knob" you mean the two big physical knobs on the top panel labled "Input 1" and "Input 2"?
Click to expand...

Yes.

Richard Crowley said:
No it is DEFINITELY NOT the case that the gain knob raises the noise floor more than "sensitivity" does. If that is what you are hearing, then it is almost certainly the case that the input gain (which Roland calls "sensitivity") is adjusted TOO LOW.
Click to expand...

So by that logic it would be illogical (in most circumstances) to use anything but the highest "sensitivity" setting? And you're saying that my reasoning about "digital" was right: the gain knobs don't do anything to the signal electrically-wise, they can only boost (gain) what is already in the signal. This is a digital post process inside the recorder. Which makes sense regarding the noise. If the actual gain is set to low then adjusting the gain digitally will just raise the noise floor equally together with other parts of the signal, ie. it wont change the signal to noise ratio - as it wont change the mics sensitivity only bost what was already captured. LOL now I see the reasoning behind naming the input gain sensitivity. Especially considering that Roland is more a consumer part of the company (right? Edirol is pro?) it would make sense for them to name it like that.
 
KINOKS said:
This is a digital post process inside the recorder. Which makes sense regarding the noise. If the actual gain is set to low then adjusting the gain digitally will just raise the noise floor equally together with other parts of the signal, ie. it wont change the signal to noise ratio - as it wont change the mics sensitivity only bost what was already captured. LOL now I see the reasoning behind naming the input gain sensitivity. Especially considering that Roland is more a consumer part of the company (right? Edirol is pro?) it would make sense for them to name it like that.
Click to expand...

This actually only makes sense if half of the knob value is attenuation and the other half is "digital" gain. So for values under 50 it's attenuating the signal and for values over 50 it's boosting it. I think this correlates with my experience of using it. As noise starts creeping in when pushed over 50% (this is the middle of the knobs "path").
Does this make sense?
 
KINOKS said:
So by that logic it would be illogical (in most circumstances) to use anything but the highest "sensitivity" setting?
Click to expand...
No, absolutely not. If there were only one logical setting, they wouldn't bother making it a user-control! The whole point of the first stage (mic preamp) gain adjustment is to accommodate a wide range of signal input levels. You might have anything from nearly line-level (nearly 1 volt) down to a very faint signal measured in millivolts. And that input gain ("sensitivity") adjustment is what "normalizes" it to the standard signal levels used inside the device (the Roland recorder in this case).

And you're saying that my reasoning about "digital" was right: the gain knobs don't do anything to the signal electrically-wise, they can only boost (gain) what is already in the signal.
Click to expand...
Sorry, No, No, and No.
It is almost impossible that the input-stage gain control ("sensitivity" in Roland-speak) is digital. It almost certainly uses an internal control voltage to vary the gain of the ANALOG input stage. It is almost impossible to do that in a digital stage because the Real Analog World has a MUCH MUCH WIDER dynamic range than any digital audio circuit.
The front-panel "Input 1/2" knobs most certainly do something electrically-wise. Repeating ALL THOSE OTHER CONTROLS ARE ATTENUATORS, and that includes the "Input 1/2" knobs on the front-panel. They never "boost" the signal, they only attenuate. They allow you to select some portion of the signal to properly set the recording level.

This is a digital post process inside the recorder. Which makes sense regarding the noise. If the actual gain is set to low then adjusting the gain digitally will just raise the noise floor equally together with other parts of the signal, ie. it wont change the signal to noise ratio - as it wont change the mics sensitivity only bost what was already captured. LOL now I see the reasoning behind naming the input gain sensitivity. Especially considering that Roland is more a consumer part of the company (right? Edirol is pro?) it would make sense for them to name it like that.
Click to expand...

I'm glad it makes sense to you, because it makes no sense at all to me. Nobody else (even low-price consumer brands) use the term "sensitivity" for input gain that I have ever seen. And perhaps you can see why. Because there would be hundreds of other users out there just as confused as you are.

Repeating for the last time: It is the gain setting ("sensitivity" in Roland-speak) of that first stage (mic preamp) that establishes the dynamic range of the incoming signal and positions it properly above the noise floor of the recorder, and below the clipping ceiling of the recorder. The front panel "Input 1/2" knobs provide an operational, real-time adjustment of the Record Level to perform fine control over the recording level.

I would bet that ALL of this circuit function, the input gain ("sensitivity") control, AND the record-level controls ("Input 1/2") are done in the ANALOG DOMAIN before it ever reaches ANY kind of digital circuit. The reason for this is because that gain/"sensitivity" and record-level/"Input 1/2" adjustment must happen FIRST to get the analog signal within the range that the analog to digital converter can handle.
 
KINOKS said:
Yes.



So by that logic it would be illogical (in most circumstances) to use anything but the highest "sensitivity" setting? And you're saying that my reasoning about "digital" was right: the gain knobs don't do anything to the signal electrically-wise, they can only boost (gain) what is already in the signal. This is a digital post process inside the recorder. Which makes sense regarding the noise. If the actual gain is set to low then adjusting the gain digitally will just raise the noise floor equally together with other parts of the signal, ie. it wont change the signal to noise ratio - as it wont change the mics sensitivity only bost what was already captured. LOL now I see the reasoning behind naming the input gain sensitivity. Especially considering that Roland is more a consumer part of the company (right? Edirol is pro?) it would make sense for them to name it like that.
Click to expand...

Since I'm just a bystander in this, don't have this recording device... I was of course confused by the use of the term 'sensitivity' control... but from Crowley's description it seems it is analog gain for the input amplifier.

To use round numbers... if the noise floor is 1 volt and the signal is 5 volts above that noise floor, one has an SNR of 5... setting a 2x gain, will move the noise floor up to 2 volts, the signal up to 10 volts, but the SNR is the same, namely 10/2 = 5...

The object lesson here is to change the SNR, one has to change the sensitivity of the device, or change the position of the mic, to have a stronger signal, relative to the noise floor of the mic + amp.

Analog filtering may allow for some 'noise' to be reduced before digitizing, relative to the desired signal, and in the digital domain there may be DSP processing to get 'better' wanted signal over unwanted signal...

Personally I think it is weasel wording to call something 'sensitivity' that is in fact 'gain'.
 
Richard Crowley said:
Sorry, No, No, and No.
It is almost impossible that the input-stage gain control ("sensitivity" in Roland-speak) is digital. It almost certainly uses an internal control voltage to vary the gain of the ANALOG input stage. It is almost impossible to do that in a digital stage because the Real Analog World has a MUCH MUCH WIDER dynamic range than any digital audio circuit.
The front-panel "Input 1/2" knobs most certainly do something electrically-wise. Repeating ALL THOSE OTHER CONTROLS ARE ATTENUATORS, and that includes the "Input 1/2" knobs on the front-panel. They never "boost" the signal, they only attenuate. They allow you to select some portion of the signal to properly set the recording level.

Repeating for the last time: It is the gain setting ("sensitivity" in Roland-speak) of that first stage (mic preamp) that establishes the dynamic range of the incoming signal and positions it properly above the noise floor of the recorder, and below the clipping ceiling of the recorder. The front panel "Input 1/2" knobs provide an operational, real-time adjustment of the Record Level to perform fine control over the recording level.

I would bet that ALL of this circuit function, the input gain ("sensitivity") control, AND the record-level controls ("Input 1/2") are done in the ANALOG DOMAIN before it ever reaches ANY kind of digital circuit. The reason for this is because that gain/"sensitivity" and record-level/"Input 1/2" adjustment must happen FIRST to get the analog signal within the range that the analog to digital converter can handle.
Click to expand...

Sorry, you miss understood. I meant that the gain knobs, the big round knobs at the front of the recorder are digital gain. I understand that sensitivity setting is analog.
And later I said that it only makes sense for the knobs to be digital if it's attenuating the signal when the knob is set below the value of 50 and boosting when set above 50. Kindly check my last 2 posts again about what I meant:)

In any case thanks for having the patience and for explaining all of this!
 
No, it is virtually impossible that the front-panel controls are operating in the digital domain. You must adjust the level of the audio in the analog domain to fit within the (rather narrow) window of the analog to digital converter.

And while perhaps of some academic interest, it wouldn't matter how ANY of the controls worked (analog or digital), the requirement remains to do proper GAIN STAGING at EVERY step in the chain.
 
Why not? For example Edirol 44 has digital knobs at the front. One of the 2 knobs is I think digital.
If the front knobs arent digital then what is the difference between the menu setting "sensitivity" and the input 1 and input 2 knobs? I'm thoroughly confused now!:) It would have made sense if the input knobs were attenuation/digital gain, but if not, than what? Another analog gain that further adjusts the voltage of the signal? If this is so, than why have 2 gain setting - one in the menu and one on the knobs?

Edit: I see that Edirol 44 also has gain named under "Sens" ie. sensitivity.
 
Actually Richard I can see that the "sensitivity" (I'm with you on the stupidity of the miss naming) would certainly be analog. But it's entirely possible that the level is a digital function. It is on some devices. The first is where you are optimising the signal for the converters the second is balancing to the record section. They could both be analog but I can see the argument for either.

Kinoks,

The signal coming to the recorder is what it is. The recorder is not going to change what you mic is putting out.

The first stage (usually called mic gain or trim or... anything but sensitivity) will usually have a more noticeable effect on level. It needs to be able to handle everything from very low level dynamic mics to very hot condensers so it usually has a BIG range. The second level setting is usually set up so that someplace around 75% it is doing nothing and letting the signal out of the preamp pass through untouched. Below that position it is attenuating the signal and above that position it is amplifying the signal. Some where beyond the 75% position you generally start hearing a lot of noise. How much and when it becomes a problem is VERY brand/ model specific. Some high end gear there is hardly any added noise and on some consumer gear the top 15% or so is basically useless.

In an analog world the first stage adjusts the preamp gain and the second adjusts the signal after it leaves the preamp. Exactly how far after depends on the device. This could be in the digital domain. The logic for that would be you are optimising the signal into the A/D converter so you are getting the best performance out of the converter all the time. Plus if there is any digital processing on the device like EQ you are going to want that done before the level adjust. So it could make sense for that to be digital OR it could be analog after the digital, but then you would need to re digitize to record and that would be dumb.

The logic for it being all analog would put it between the pre and the A/D converter. All processing would need to be analog before the level control.
THe down side would be that as you feed the converter les and less signal it has less info to work on and effectively lowers your bit rate.

Which approach makes the most sense depends on the signal flow and costs. If the level control is really just a fine trim then it probably is analog before the converter. If it's in a processing chain that is digital it is probably digital. If you can fade the signal all the way out with the level control I would lean toward digital but? THe cost factor is that it is a LOT cheaper to make high quality digital signal processing these days than analog ones. So in budget devices these days it's a lot more common to see digital replace classically analog stages.

In the long run it doesn't make a lot of difference. As a user it's probably easier to assume everything is analog till it is digitized to the recording. If it's designed properly you should not be able to tell the difference. But if it's bugging you call up Roland and ask.
 
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