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compression: a tin can or automatic volume control? Dynamics Plugins
Old 19th September 2011
  #31
Gear Head
 

Quote:
Originally Posted by unitymusic View Post
I understand the distinction you are making. But to get the peak of the signal back to where it was you would have to add to the noise floor, decreasing the dynamic range of the signal to noise ratio, which is why I still think it is misleading to say compression is the same thing as a fader ride. Unless I'm just being stupid and missing something obvious. Are you saying the noise floor would not be raised?
Sorry, I should have been a little more clear. I was mainly trying to address your statement "That would not be attenuating the whole signal."

Fundamentally speaking, nothing is raised in the process of compression. The only way something is raised is if makeup gain is applied. Of course, makeup gain is commonly used--many applications of compression have the primary goal of increasing the perceived volume of the track--but it shouldn't be assumed when talking about compression in general.
Old 19th September 2011
  #32
Lives for gear
Maybe it helps to be more careful with terminology. Gain is the ratio by which a signal is changed. Typically positively in an amplification stage. 0.1v in results in 1v out. Attenuation is merely a reduction in signal amplitude. e.g. that 0.1v signal being reduced to 0.05v. It doesn't change the gain, only the relative level.

Compressors are basically proportional attenuators. The greater the compression ratio set, the more the signal is proportionally attenuated. In effect changing the apparent gain ratio for signals when the threshold is exceeded and the compressor invoked.

The "gain" above threshold is set by the compressor ratio. That degree of attenuation that happens proportional to the signals level. The gain isn't dynamic even though many compressors indicate "gain reduction". What they are indicating is the degree above threshold the signal is going and thus the proportional attenuation in signal level for the compression ratio chosen.

Arrghh. This is hard to explain without getting more confusing.
Old 19th September 2011
  #33
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Quote:
Originally Posted by mightypants View Post
Sorry, I should have been a little more clear. I was mainly trying to address your statement "That would not be attenuating the whole signal."

Fundamentally speaking, nothing is raised in the process of compression. The only way something is raised is if makeup gain is applied. Of course, makeup gain is commonly used--many applications of compression have the primary goal of increasing the perceived volume of the track--but it shouldn't be assumed when talking about compression in general.
I do understand that something is only raised when makeup gain is applied, but all compressors have makeup gain, so even if you don't apply it I would think it would be fair to include it as a possibility. At least more fair than saying compression is the same as a fader ride by default. Anyway, I don't want to get into semantics, thanks for the clarifications, I think I get it.
Old 19th September 2011
  #34
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Aisle 6's Avatar
Quote:
Originally Posted by unitymusic View Post
I thought that was why it was considered a dynamics processor, and also assumed that is why some people like Bruce would opt to use fader rides instead of a compressor. Not because they are the same exact thing, but because you can accomplish the "gain control" without affecting the dynamic range.
Even if you use fader rides to reduced louder parts and fader rides to increase softer parts, the dynamic range has definitely been reduced. Exactly like a compressor.
Old 20th September 2011
  #35
Registered User
Quote:
Originally Posted by Aeolian View Post
Maybe it helps to be more careful with terminology. Gain is the ratio by which a signal is changed. Typically positively in an amplification stage. 0.1v in results in 1v out. Attenuation is merely a reduction in signal amplitude. e.g. that 0.1v signal being reduced to 0.05v. It doesn't change the gain, only the relative level.

Compressors are basically proportional attenuators. The greater the compression ratio set, the more the signal is proportionally attenuated. In effect changing the apparent gain ratio for signals when the threshold is exceeded and the compressor invoked.

The "gain" above threshold is set by the compressor ratio. That degree of attenuation that happens proportional to the signals level. The gain isn't dynamic even though many compressors indicate "gain reduction". What they are indicating is the degree above threshold the signal is going and thus the proportional attenuation in signal level for the compression ratio chosen.

Arrghh. This is hard to explain without getting more confusing.
I think you are overthinking this.

Gain, Level, Volume - just synonyms for the same thing.

Technically, the device might be an attenuator rather than a gain stage, but we can talk about 'negative gain' to describe this accurately.

A fader has a zero point - above that, it's increasing gain, below that it's decreasing gain. End result is an increase or decrease in level, hence volume.

A compressor is an automatic gain control - period. The differences we can argue about are speed, timing and amount. This can all be summed up by describing the compression envelope, and obviously there are worlds to be explored, but it all comes to: Automatic, Gain, Control.
Old 20th September 2011
  #36
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Quote:
Originally Posted by Kiwi View Post
I think you are overthinking this.

Gain, Level, Volume - just synonyms for the same thing.

A fader has a zero point - above that, it's increasing gain, below that it's decreasing gain. End result is an increase or decrease in level, hence volume. .
This is what I was trying to separate. A fader is not a gain control. It does nothing to affect the gain of the stage following it. It only changes the amplitude necessary at the input in order to achieve a given amplitude at the output.

Gain is a ratio. An amplification stage with a higher gain will increase the amplitude of a given input to a higher level. This has nothing to do with any various "volume controls" in the chain. It also has nothing to do with the ultimate output level. You can have a power amplifier with 25dB of gain that has the current capability to drive 1000 watts into a speaker, while another amp with 30dB of gain may run out of gas at 250W into the same speaker load.

So what a compressor is doing when tripped into action, is changing (depending on the compression ratio setting) the gain ratio. Requiring proportionally more input for a given output.

While tripped, the gain gets reduced, not just the volume level. Sounds that were twice as loud come out only half again as loud. And everything beneath them gets the same proportional treatment. Some background part that may have punched it up a bit will be proportionally reduced. The further down in the mix it is, the less effect the reduction in gain will have. Everything gets closer together until the input drops below the threshold and the compressor releases. The quiet parts don't get louder, it's just that their ability to get louder gets reduced by a lesser degree than the loud parts.

Pulling a fader only turns down the level of everything together.

I think I may have contradicted my earlier posts. But this has made me think through what is happening and increased my understanding of these gadgets.
Old 20th September 2011
  #37
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Quote:
Originally Posted by Capproach
Bingo. Thanks, PRobb. That is completely making sense now. Thanks to everyone for weighing in. Forgive me for creating such a stupid thread. ...
Phooey. This is good exorcize- both in the teaching and learning. Look at all the good stuff that got stirred up in the process.

Quote:
Originally Posted by travisbrown View Post
Yes, no, sort of.
Attack = Sometimes explained as how long the signal is allowed to go over before the compressor kicks in, but this is technically wrong. The attack time is the amount of time it takes from the time the compressor kicks in to the time it reaches its intended gain reduction.

..snip
... Don't think of compressor setting as slow or fast; think of them as long and short. It's easier to visualize the shape of the sound this way.
I guess I hadn't thought about this specifically for a while, but what you say regarding attack not being a 'delay factor makes sense.
Attack settings can be shown in time or db, but presumably (except in some cases?) can be seen as slope –steep or gradual (linear or not I suppose) along the horizontal time line.
Superimposing that against a given waveform shape gives an indication of how that attack slope might ignore, cross through or clamp down on a portion or more of a signal.
Does that sound about right?
Then it would seem (help me here) that the steepness of the slope (time vs level) is actually a mix of ratio and attack?
Old 20th September 2011
  #38
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Quote:
Originally Posted by Aeolian View Post
...Sounds that were twice as loud come out only half again as loud. And everything beneath them gets the same proportional treatment. Some background part that may have punched it up a bit will be proportionally reduced. The further down in the mix it is, the less effect the reduction in gain will have. Everything gets closer together until the input drops below the threshold and the compressor releases. The quiet parts don't get louder, it's just that their ability to get louder gets reduced by a lesser degree than the loud parts.
Pulling a fader only turns down the level of everything together.

I think I may have contradicted my earlier posts. But this has made me think through what is happening and increased my understanding of these gadgets.
I may be misunderstanding you here, but it seems you've contradicted the fact that during the compressor's action (below the threshold) all of the sounds high or low in the mix move in level as one- no inter-proportional relation changes there. Only in relation to other parts of the signal on the time line.
?
And again and still- just like grabbing a gain control.
Old 20th September 2011
  #39
Registered User
A good "exorcize" indeed ... begone, foul demons from hell!

A good "exercize" is to experiment with a compressor over a drum loop - even a single hit snare looping.

Note that the Attack basically is a period of time where the compressor does not respond (or responds so slowly it isn't audible). During this period of time, the transient peaks go straight through (assuming the compression had already 'Released' from the previous hit).

So people hoping that using a compressor will stop digital clipping are misguided - it is never about that. It actually make it worse, because invariably people add Make Up Gain to compensate for the fact that a compressor "compreses" ... so those peaky transient spikes get boosted by Make Up Gain ... think about that.

This is why - if in doubt - don't track with a compressor. Some limiters are fast enough - different story.
Old 20th September 2011
  #40
Gear Guru
Threshold- below this level nothing happens. Once the signal goes above this level, something happens.
Ratio is the first thing to look at. A ratio of 4:1 means for every 4dB over threshold of input, there will be 1 dB over threshold of output. So if the threshold is 6 and the input hits 10, that's 4 over. So the output wants to be 5 (1 over). So the gain has to be reduced 5. How fast the fader gets yanked down is the attack time.
Now the input goes back under threshold, so the fader (which is now at -5) has to go back to 0 (no change). How fast it gets pushed up is the release time.
Attack and release times are generally calibrated in milliseconds.

That's a bit simplified, but that's the basics.
Old 20th September 2011
  #41
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travisbrown's Avatar
Quote:
Originally Posted by Wayne View Post
Phooey. This is good exorcize- both in the teaching and learning. Look at all the good stuff that got stirred up in the process.



I guess I hadn't thought about this specifically for a while, but what you say regarding attack not being a 'delay factor makes sense.
Attack settings can be shown in time or db, but presumably (except in some cases?) can be seen as slope –steep or gradual (linear or not I suppose) along the horizontal time line.

Superimposing that against a given waveform shape gives an indication of how that attack slope might ignore, cross through or clamp down on a portion or more of a signal.
Does that sound about right?
Yup. The steeper the slope, the faster the attack/release.

Though it wouldn't ignore or cross through; it conforms (i.e. reshapes) the signal.

Old 20th September 2011
  #42
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Quote:
Originally Posted by Kiwi View Post
A good "exorcize" indeed ... begone, foul demons from hell!..
Hah! thank you. It knew it didn't look right
Old 20th September 2011
  #43
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Quote:
Originally Posted by travisbrown View Post
Yup. The steeper the slope, the faster the attack/release.

Though it wouldn't ignore or cross through; it conforms (i.e. reshapes) the signal. ..
Cross through' as in if a signal's front end or transient is rising within the attack time's ramp down in level.
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