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What is an Optical Compressor and How Do I use it Dynamics Processors (HW)
Old 23rd March 2007
  #1
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What is an Optical Compressor and How Do I use it

Hey Whats up, I tried searching the forums but could not find too much...

I need a better understanding as to what an Optical compressor is as well as how to use it. Thanks
Old 23rd March 2007
  #2
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luctellier's Avatar
It's a type of audio compressor that uses an electro optical attenuator to control the dynamics of the processed signal. An electro optical attenuator basically consists of a light source whose intensity is proportional to the level of the input signal, and a photoconductive cell whose resistance decreases as the light intensity presented to it increases. This photoconductive cell controls the volume of the amplifier that attenuates the volume of the output signal. Thus when a louder signal is input, the light shines brighter, the photocell's resistance goes down, and the amplifier reduces its gain, producing the effect of audio compression - for each dB that the input signal exceeds the threshold, the output rises by something less than a dB depending upon how the ratio is set and the exact properties of the photo cell circuit being used.
Old 23rd March 2007
  #3
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So What would I use optical compression on and is there a big difference between optical and electro?
Old 23rd March 2007
  #4
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luctellier's Avatar
Source: http://www.sweetwater.com/expert-cen.../d--05/10/2004

Compressor vs. Leveler!
05/10/2004

Q: "Why Would I Use Compressor Instead Of A Leveler And Vice Versa?"


A: There are some famous compressors and levelers out there in the audio world whose names seem to come up all the time when producers and engineers let the 'feline out of the rucksack' when it comes to their secret sonic weapons. Two of the most famous, the 1176 compressor and the LA-2A Leveling Amplifier are both now manufactured by the same company, Universal Audio, which naturally begs the question; What's the difference between a compressor and a leveler (leveling amplifier), and why would I use one or the other?


First, let's determine what distinguishes one from the other, since it's the job of both to 'ride gain.' Or, as gadget-girl would put it: employ a variable gain amplifier to reduce the dynamic range of the program material. (Spare us the techno-babble, gadget-girl) Simply put, in music, 'dynamic range' is the difference between the quietest and loudest volume of an instrument, part or piece of music, and it is the job of a compressor or leveler to compress, or limit the dynamic range so that the soft parts are not too soft, and the loud parts don't pin the meters (distort the music) or make your ears bleed.


First, lets define what limiting is. A limiter is a circuit that allows signals below a set value to pass unaffected, and clips off the peaks of stronger signals that exceed this set value. (Or, as a limiter would put it; "You can only go so loud and no louder, or I will taunt you a second time.") The basic difference between the two is that a leveler functions more like a limiter and is program dependant, whereas the compressor has the ability to change the value at which a signal is passed or compressed (threshold), as well as the speed at which the compressor responds to a signal (attack), the ratio of input signal to output signal, (e.g. A ratio of 4:1 means if 4db in, 1db comes out. Or, think Mad Max: "Two go in, one comes out, two go in, only one comes out... ladies and gentlemen, limiting time is here!"), finally, a compressor allows you to determine the length of time that the compressor acts on the signal. (Release) When a compressor is set with a very high ratio it begins to act like a limiter. A leveler, or leveling amplifier basically has only two controls, as in the case of the LA-2A: Gain, and Peak reduction. As we said earlier, the leveler is program dependant, meaning that it acts on the totality of the music coming through it, both high and low levels, based on an internally set compression slope. What makes the LA-2A unique is that it uses an electro-optical attenuator system that allows instantaneous gain reduction. The opto-compressor is thought to be more musical since it's response is non-linear, just like the music passing through it. (For more background on optical compression characteristics see WFTD - Optical Compressor.) Some people feel that the more linear response of a VCA controlled compressor is not as musical, but in reality, both are effective tools based on the musical context you use them in, which is what we are about to discuss.


An opto-controlled leveler like the LA-2A or the Summit TLA-50 are often used on vocals and instruments like acoustic guitar because of their non-linearity in release times (as mentioned earlier). Most engineers think they are not as effective on percussion as an FET (solid state) compressor like the 1176 would be, since the ability to control attack and release times (also mentioned earlier) allows you to bring out the attack of the drums more effectively. (There are compressors that do have an electro-optical circuit, but they also have attack and release controls that do make them useful for percussion.) Perhaps the most prevalent use of a leveling amplifier is for stereo bus compression or for stereo mains output. The idea is that running your stereo mix through LA-2As or a pair of TLA-50's is the secret sauce that 'glues' a mix together, making it sound like a whole, and not just a collage of different parts. (Mastering secret revealed!)


Keep in mind, that when we compress a signal, it's volume decreases, so usually there is a gain make-up control to bring the level up. With a leveling amplifier, the gain make-up is built in to the circuit, which makes them a little harder to set. That is to say, they require a little more finesse since it's easy to overuse them, but having only two controls makes them easier to use as well. Also, since they are program dependent, there is no set rule for basic settings. Keep practicing; you'll get the hang of it.

Last edited by luctellier; 23rd March 2007 at 04:15 PM.. Reason: URL
Old 23rd March 2007
  #5
Gear Maniac
 

/QUOTE=luctellier
"Keep practicing; you'll get the hang of it."[/QUOTE]

Best advise ever given!
Old 23rd March 2007
  #6
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Thanks Guys!!!!!!
Old 24th March 2007
  #7
Gear Nut
 
1954U1's Avatar
 

And thats why, maybe, our ears thinks analog sound is better.
Nonlinearity = curves.
We love curves.
Old 24th March 2007
  #8
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Curve Dominant's Avatar
Quote:
Originally Posted by 1954U1 View Post
And thats why, maybe, our ears thinks analog sound is better.
Nonlinearity = curves.
We love curves.
Thank you very much!
Old 24th March 2007
  #9
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stagefright13's Avatar
 

Greatest response ever
Old 24th March 2007
  #10
Gear Guru
 
u b k's Avatar
 

except that running your mix thru two la-2a's won't, in all likelihood, sound so great. besides the fact that they don't track in stereo, they're just not good at dense program material. neither are most opto's, imo.

some optos are more versatile than others; the langevin el-op is so damn fast on the uptake and release that it practically nullifies transients, making it lovely on vocals and bass but fairly useless on drums and percussion, and it distorts too much to be of use on acoustic guitars. the la-3a, otoh, kills on just about everything except drums. the la-2a not only rocks on vocals, acoustics, and bass, it also does amazing things to certain kick drums in certain songs.

in short, the answer to your question can't really be appreciated until you've used these things, and understand with your ears what it means for an la-2a to be both faster and slower than an 1176.


gregoire
del
ubk
.
Old 24th March 2007
  #11
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vernier's Avatar
In the circuit is a tiny light, when it comes on the audio signal gets attenuated ..those compressors are totally boring imo. If you have to have one of everything, then maybe an original LA2A, but that unit is nice because of the way it sounds (aside from the part that compresses) ..and a good vari-mu will have that and exciting compression ..so, a good vari-mu is all you need.
Old 24th March 2007
  #12
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bcgood's Avatar
 

Quote:
Originally Posted by u b k View Post
except that running your mix thru two la-2a's won't, in all likelihood, sound so great. besides the fact that they don't track in stereo, they're just not good at dense program material. neither are most opto's, imo.

some optos are more versatile than others; the langevin el-op is so damn fast on the uptake and release that it practically nullifies transients, making it lovely on vocals and bass but fairly useless on drums and percussion, and it distorts too much to be of use on acoustic guitars. the la-3a, otoh, kills on just about everything except drums. the la-2a not only rocks on vocals, acoustics, and bass, it also does amazing things to certain kick drums in certain songs.

in short, the answer to your question can't really be appreciated until you've used these things, and understand with your ears what it means for an la-2a to be both faster and slower than an 1176.


gregoire
del
ubk
.
ubk I've read many of your posts and enjoy your input in this forum. I'm interested to hear something that you have engineered. Do you have any mp3's or cd's out there that I could get my hands on or could you post one on here?

Thanks in advance I'm just curious. I like to read about recording but to me I like to hear what someone has engineered and then learn about what they did after the fact. I'm just interested since I've read so many of your posts but I've never heard anything that you've recorded.

Thanks,

bcgood
Old 24th March 2007
  #13
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Mike Jasper's Avatar
Here's a little sidebar to all of this: I'd always heard that the LA2A and Tube-Tech CL 1B were similar, since they're both tube based, opto-cell compressors. But that sure isn't true at all, as least as far as sound goes. I had the opportunity to try them head-to-head on bass, and was surprised how different they sounded.

Jasper
Old 24th March 2007
  #14
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Curve Dominant's Avatar
Interesting how opto comps are now classified as "Low End" here on Gearslutz.
Old 24th March 2007
  #15
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Mike Jasper's Avatar
Quote:
Originally Posted by Curve Dominant View Post
Interesting how opto comps are now classified as "Low End" here on Gearslutz.
Good point, Eric. I didn't even notice the forum. I just went for the topic.

Jasper
Old 24th March 2007
  #16
Moderator
 
toolskid's Avatar
 

Quote:
Originally Posted by AnAverageJoe View Post
Hey Whats up, I tried searching the forums but could not find too much...

I need a better understanding as to what an Optical compressor is as well as how to use it. Thanks

I think this is one?
Attached Thumbnails
What is an Optical Compressor and How Do I use it-eyelash.jpg  
Old 25th March 2007
  #17
Gear Guru
 
u b k's Avatar
 

Quote:
Originally Posted by bcgood View Post
ubk I've read many of your posts and enjoy your input in this forum. I'm interested to hear something that you have engineered. Do you have any mp3's or cd's out there that I could get my hands on or could you post one on here?

putting the money where the mouth is, everyday!


me, circa 12 months ago:

http://www.everydayclarity.com/ubk/ubk-haunts.mp3


a little hip hop i wrote and produced/mixed, with an artist named Reminisce on vocals.

http://www.everydayclarity.com/ubk/r...ce-avatars.mp3


my top-to-bottom recreation of the beatles for my 66 year old dad to sing on and give to my mom for their 40th anniversary.

http://www.everydayclarity.com/ubk/s...for_martha.mp3


all those mixes were pre-focal twin 6's, when i listen to them on the focals i hear 30 things i'd do differently, but they're still great mixes. can't WAIT to start hammering out the new EP with the focals!


gregoire
del
ubk
.
Old 25th March 2007
  #18
Lives for gear
 
bcgood's Avatar
 

Quote:
Originally Posted by u b k View Post
putting the money where the mouth is, everyday!


me, circa 12 months ago:

http://www.everydayclarity.com/ubk/ubk-haunts.mp3


a little hip hop i wrote and produced/mixed, with an artist named Reminisce on vocals.

http://www.everydayclarity.com/ubk/r...ce-avatars.mp3


my top-to-bottom recreation of the beatles for my 66 year old dad to sing on and give to my mom for their 40th anniversary.

http://www.everydayclarity.com/ubk/s...for_martha.mp3


all those mixes were pre-focal twin 6's, when i listen to them on the focals i hear 30 things i'd do differently, but they're still great mixes. can't WAIT to start hammering out the new EP with the focals!


gregoire
del
ubk
.
Hey thanks for the mp3 post ubk, very cool! I like many elements in both of the recordings. I really like the sound you got for the drums in the Beatles song!

Could you describe how you recorded those drums? I also think you nailed the guitar tone, thanks again.

bcgood
Old 21st October 2011
  #19
Lives for gear
 
hereticskeptic's Avatar
Quote:
Originally Posted by u b k View Post
putting the money where the mouth is, everyday!


me, circa 12 months ago:

http://www.everydayclarity.com/ubk/ubk-haunts.mp3


a little hip hop i wrote and produced/mixed, with an artist named Reminisce on vocals.

http://www.everydayclarity.com/ubk/r...ce-avatars.mp3


my top-to-bottom recreation of the beatles for my 66 year old dad to sing on and give to my mom for their 40th anniversary.

http://www.everydayclarity.com/ubk/s...for_martha.mp3


all those mixes were pre-focal twin 6's, when i listen to them on the focals i hear 30 things i'd do differently, but they're still great mixes. can't WAIT to start hammering out the new EP with the focals!


gregoire
del
ubk
.
I'd love to hear these mixes!
Old 21st October 2011
  #20
Gear Addict
 
Doc No's Avatar
Quote:
Originally Posted by toolskid View Post
I think this is one?

Old 13th August 2013
  #21
Gear Nut
 

...so back to the question. Is one differece with optical or not is you can adjust slope. Where with a slower non optical you cant? I vaguely remember something like that.
I think having an optical compressor is good. They are more responsive I hear...speed of light.Ive got some joemeeks. David Wills has made a dvd for sale on compressors and how to use them.
I think the compressor shouldnt be overused. I believe in player dynamic control but also having a studio strip to smooth everything out and make sure the take is good. I think that is being professional. Time is money.

When **** goes in, **** still comes out. Because you cant polish a turd.
Old 7th May 2016
  #22
Gear Maniac
 
Roloalcien's Avatar
What about the Grace Design m502 compressor?

It has release,attack,threshold and ratio settings

Is it like a combination of a VCA and an optical?
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