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[mixsit]

Quote:

Wayne, Thanks for testing these examples out. As you noted, threshold is not the same as  "rotation point". Rotation point is an arbitrary concept and it exists at unity gain. If you set the dbX 160 threshold at -20dB and the ratio at 2:1, send a 0dB signal to the compressor and add enough makeup gain to acheive an output level of 0dB, you will find that gain is added as you reduce the level below 0dB and gain is reduced as you increase the level. You will notice that the 610 is different than the 160 (dyslexics beware!)

Ok, as you said, with the above setup, on the 160 as I reduce the input, the output goes down 2:1 as expected.
-10= -5
-15= -8
-20= -10
The 610 does essentially the same, but without having to add the 20 dB at the output. (The output looses only a few dB at the transitions into gain reduction.)
So it looks to me that where 'Valley says "Note that the compressor adds gain to signals below the threshold. At threshold (it) adds less gain up to the rotation point (unity gain). As the input exceeds the rotation point (it) begins to attenuate.."
And, "Compression is .. increasing the gain of the processing signal chain in the presence of signals below a given threshold" is incorrect and should be ' ..below a given rotation point and stops adding gain below the threshold? Or in the case of dbx, only if you add it in to make up for it?

Thanks for putting up with me here. I admit to this being a bit frustrating every time I've gotten into this.

Quote:

Morgan puts it this way in the paper: "The rotation point is the locus on a graph of the compressor's transfer function at which the gain control elements exhibits unity gain, and through which all lines derived from data describing the device's output level as a function of input level will pass. A limiter, in the purest sense, adds no gain and has no rotation point."

This part falls in exactlly with Valley'.
Wayne Smith

[steve parker]

zmix,
is the difference between you and ronny that you are considering make-up gain part of the system and he is not?
or are you saying that a compressor with make-up gain knob left alone still increases volume below the threshold?

I'm not trying to bait...
I think i know how a compressor works and ronny or the dc's link is it..
but...i've found before that the reality is subtly different from the obvious in audio.

steve.

[mixsit]

I'm getting this nagging feeling that the reason they made 'rotation and 'threshold separate points is to make the graphs work better.

[steve parker]

Quote:

I'm getting this nagging feeling that the reason they made 'rotation and 'threshold separate points is to make the graphs work better.

but with soft-knee, gain reduction *will* start below the threshold, so (assuming make-up) there would be a single point of unity gain below the threshold.
?

Steve

[tom eaton]

I asked:

"So, let's say you have a threshold of -5dB, ratio of 2:1 and add 10dB of makeup gain. What happens to a signal that enters the compressor at 0dB? Does it get louder or softer? "

And Z replied:

"The level in the above case will exit the compressor 12.5dB hotter than it went in. "


I am baffled by your math!  How does a signal which is being compressed and turned up 10dB get 12.5dB louder?  The correct answer is it will exit the compressor 7.5dB louder.   The signal is over threshold by 5dB, at a 2:1 ratio, resulting in gain reduction of 2.5dB against the makeup gain of 10dB.

I specified the makeup gain specifically to exclude the idea of "auto" make-up gain...

The fact that you ackowledge that a compressor with make up gain can increase the level of a signal above threshold is a change from a previous post in which you stated:

"There is a rotation point at 0dB, below which gain is added and above which gain is reduced."

That statement can ONLY be true when make-up gain is in use AND under circumstances where the compression over-rides the make-up gain.


-t

[Jerry Tubb]

I use the Manley Vari Mu every day for mastering.

Initially I shoot a 1k tone thru it, get a level, balance the L/R, and go to work.

Never even think about the numbers (anymore) you guys are debating.

Just turn the knobs til it sounds good, occasionally look at the gain reduction meters.

Slow attack, medium release, usually unlinked, adjust the input according to the level I want for the song...

6dB of gain through this unit sounds great.

I like the fact that there aren't any numbers on the front panel, forces you to use your ears.

Been using the Vari Mu for almost a decade, guess it's become intuitive... instinct.

A simple "meat & potatoes" approach... usually sounds great..

I'm not encouraging young budding MEs to go Willy Nilly, they should study hard, learn the theory, and find a gig.

Happy Easter Egg.

[dcollins]

Jerry Tubb wrote on Sat, 15 April 2006 22:47

am I missing something?

Tight bottom with low distortion?

DC

[Jerry Tubb]

dcollins wrote on Sun, 16 April 2006 01:40

Tight bottom with low distortion?

Oh, your assessment of the Manley's weaknesses?

Compared to what... the Pendulum?

Guess that all depends on how you use it.

One Man's Trash, Another Man's Treasure...

JT

[zmix]

TER wrote on Sat, 15 April 2006 18:54

I asked: "So, let's say you have a threshold of -5dB, ratio of 2:1 and add 10dB of makeup gain. What happens to a signal that enters the compressor at 0dB? Does it get louder or softer? " And Z replied: "The level in the above case will exit the compressor 12.5dB hotter than it went in. " I am baffled by your math!  How does a signal which is being compressed and turned up 10dB get 12.5dB louder?  The correct answer is it will exit the compressor 7.5dB louder.   The signal is over threshold by 5dB, at a 2:1 ratio, resulting in gain reduction of 2.5dB against the makeup gain of 10dB.

Jesus f*ck! It was a simple typo.. of course 7.5 dB gain is correct... keep your shirt on.

Quote:

I specified the makeup gain specifically to exclude the idea of "auto" make-up gain... The fact that you ackowledge that a compressor with make up gain can increase the level of a signal above threshold is a change from a previous post in which you stated: "There is a rotation point at 0dB, below which gain is added and above which gain is reduced."

Threshold and rotation point are not the same thing... what is your point here??

[AndreasN]

Awww.. C'mon. Reply, please! =)

Is your idea of a rotation point inextricably linked to the auto make up gain of Morgans design, or not? In other words, will the rotation point behave as described without auto-make up gain?



Andreas

[steve parker]

steve wrote (wrongly...):

Quote:

but with soft-knee, gain reduction *will* start below the threshold, so (assuming make-up) there would be a single point of unity gain below the threshold.

as has been pointed out to me privately, the above statement is of course (and obviously) wrong.
Make-up gain could put the point of unity above, on or below the threshold - I was thinking of a particular case and really just meant to say that the point of unity need not be the threshold.

There is enough confusion here without me adding to the mix..  ;-(


Zmix, I'm with Andreas in asking how it all works without make-up gain?

Steve.

[Ronny]

Everything that I've been relating is mirrored in this DBX paper, including:

From DBX:

Threshold
The THRESHOLD knob sets the level where compression will begin. As long as the input signal level is below the Threshold level, the compressor will do nothing to the signal. Once the input signal crosses the Threshold, the compressor will begin compressing at a ratio set by the ratio control.

Exactly what I've said.

Ratio
The RATIO knob controls the amount of compression, which will happen once the input signal crosses the Threshold level, described above. Ratio controls how much the input
signal will be reduced as a ratio of the input signal level. For example, if the compression ratio is set for 6:1, the input signal will have to cross the threshold by 6 dB for the output
level to increase by 1 dB. the maximum setting is typically labeled: 1 (infinity to 1),and is also called Limiting. This means that the output signal won’t increase at all, no matter how far above the threshold the input signal goes.

Exactly what I've been saying.

Attack
The ATTACK knob controls the amount of time before compression starts after the threshold is exceeded by the input signal.The range of this control can go anywhere from very slow (about 1dB/Sec) to very fast (about 400dB/Sec). Long attacks are useful for percussive sounds, where shorter attacks are good for melodic parts like vocals and strings. The Attack control is also useful for keeping the transients on percussive drum or bass sounds. Experiment with different short attack times on snare drums to get more or less of
the “stick” attach.

Release
The RELEASE knob controls the amount of time the compressor takes to stop compressing after the signal crosses below the threshold. the range of this control can be from approximately
4000dB/Sec to 10dB/Sec. Short release times are good for percussive, punchy sounds,where longer release times can make compression less obvious on vocals. Adjusting the release time may be necessary when using extreme compression and “pumping” or
“breathing” is audible, or if lower level signals after peaks are getting lost. See also the section on pumping and breathing explained below.


Output
The OUTPUT knob controls the level of the compressor’s output. The Output control is useful for making up gain, which was reduced by the compression circuit, or matching the
input level of a mixer or recorder. If the Gain Reduction meter shows that the input signal is being attenuated by -6dB, then the Output control generally should be set around +6dB.
This control is disabled if the [BYPASS] button is pressed.


Hard knee/OverEasy

[Pingu]

Im glad i stayed out of this one.

It pays not to have a brain.

[bblackwood]

I feel I have to ask some of the posters on this thread - is the point of this discussion to enlighten/teach/learn or to "win"?

I really hope it's the former, though I fear it's the latter...

[Pingu]

Its funny how a discussion about compression can blow up.

Here of all places.

I don't think i saw BK verify the original question.

May be he feels its self explanatory.