D
DarthFaders
New member
Like in 'opto compressor'? Just curious...
TexRoadkill
Audio Bum
There are VCA and Opto compressors. The opto's use some type of light activated circuit and generally have a more vintage sound that allows the transients to pass through uncompressed.
C
chessrock
Banned
Opto's are slower than mole-asses in January.
darrin_h2000
Banned
I assume that use of an led and a light sensing device is used.
G
Griffinator
New member
darrin_h2000 said:
Exactly. Generally it's a "black box" with an LED and a light sensor - completely sealed off from the rest of the system to prevent any mis-triggering of that light sensor.
They're pretty slow - but in a multiband, they're definitely the preferred method over VCA - transient info remaining unmolested is crucial in a multiband compressor (which is why I'm going opto in the 6-band I'm designing right now)
S
sjjohnston
New member
Opto means
"Official Pronounced Too Old."
(As seen on a patch recently worn by Paul McCartney).
"Official Pronounced Too Old."
(As seen on a patch recently worn by Paul McCartney).
C
chessrock
Banned
Griffinator said:
That's good news for the transients. I've heard there was a big scandall with Catholic Audio Engineers and young, impressionable audio signal transients being molested.
Yea, I know. That was bad.
N
Newest User
New member
ok, so is there an optical converter onboard? There must be right 
Peace,
Dennis
Peace,
Dennis
L
littledog
New member
I'm not a tech guy, by any means. Just your run of the mill musician... so if I'm a little off here maybe a heavy hitter like Knightfly or JohnBoy will straighten us all out.
But my understanding is that the opto compressor contains (as Griffinator said) a light bulb that shines more brightly as the signal gets louder. A photoelectric cell reacts to how brightly the light is shining. A brighter light (louder signal) generates more current in the photoelectric cell. It's the current from the cell that controls the amount of compression.
What gives it a different sound than straight VCA compression, is the non-linear way in which the light-photocell combination works as material gets louder. It is this non-linearity which some people find more natural sounding, and why they are desireable.
There are many excellent opto-compressors on the market today, some of them quite pricey!
OK tech guys - please correct any errors or misconceptions!
But my understanding is that the opto compressor contains (as Griffinator said) a light bulb that shines more brightly as the signal gets louder. A photoelectric cell reacts to how brightly the light is shining. A brighter light (louder signal) generates more current in the photoelectric cell. It's the current from the cell that controls the amount of compression.
What gives it a different sound than straight VCA compression, is the non-linear way in which the light-photocell combination works as material gets louder. It is this non-linearity which some people find more natural sounding, and why they are desireable.
There are many excellent opto-compressors on the market today, some of them quite pricey!
OK tech guys - please correct any errors or misconceptions!
J
Joe E
New member
The nice thing about Opto compressors
is that you don't hear them pump or breath. (no jokes please) They sound very natural, and never squashed.
You can compress a signal on a LA2a at a high ratio and the sound just gets fatter.
I recently purchase a new ART Pro VLA that works on this principle and it really sound smooth and warm. Bass guitar and vocals sound great! Not bad on acoustics as well. I beleive the LA2a, LA3, LA4 and 1176 all worked on this same design. THe difference being only the way they were built. Meaning first was point to point wiring, then printed circuit board and so on.
Most top engineers have these in thier "tool box". I guess that doesn't mean anything, except your favorite records you listen to, were at least partially recorded through a opto compressor.
is that you don't hear them pump or breath. (no jokes please) They sound very natural, and never squashed.
You can compress a signal on a LA2a at a high ratio and the sound just gets fatter.
I recently purchase a new ART Pro VLA that works on this principle and it really sound smooth and warm. Bass guitar and vocals sound great! Not bad on acoustics as well. I beleive the LA2a, LA3, LA4 and 1176 all worked on this same design. THe difference being only the way they were built. Meaning first was point to point wiring, then printed circuit board and so on.
Most top engineers have these in thier "tool box". I guess that doesn't mean anything, except your favorite records you listen to, were at least partially recorded through a opto compressor.
C
chessrock
Banned
littledog said:
This is very interesting, and not the first time I've heard this touched on. Can someone explain what is meant by this non-linearity? Do you mean that it reacts differently to the different frequencies? I'm confused. Thanks.
TexRoadkill
Audio Bum
On a graph non linear would be a curve and linear would be a straight line. A non linear volume raise would not go from quiet to maximum at the same rate over time but would start rising slowly then speed up towards the end or vice versa.
C
chessrock
Banned
Very cool. So in other words, it would almost be like the way a human might work a fader, as opposed to the way a computer might work it?
G
Griffinator
New member
chessrock said:
Bingo!
C
chessrock
Banned
Wow. This opens like a whole new world for me . . . In a real geeky sort of way, this pretty much made my week. Thank you for sharing that. This is why I come to this board. I love you guys (in a non-gay sort of way if you catch my drift).
That's exactly the sound of the compressor. And I can see it now and understand why it sounds that way. Yes! Man, do I need to get a life.
In a real geeky sort of way, this pretty much made my week. Thank you for sharing that. This is why I come to this board. I love you guys (in a non-gay sort of way if you catch my drift). That's exactly the sound of the compressor. And I can see it now and understand why it sounds that way. Yes! Man, do I need to get a life.
L
littledog
New member
I just found a really outstanding article about how the four basic different types (opto, variable-mu, FET, and VCA) of compressors work in the February 2001 Electronic Musician, by Michael Cooper. This reinforces a lot of what we already said:
To sum up the section on optos:
There is a sidechain consisting of an LED shining on a light-dependent resistor. As the volume gets louder the light gets brighter, creating a corresponding increase in compression of the audio signal. Because the LDR has an inherent "memory effect", it releases slower when the light is brighter or has been shining for a while. That means heavier or continuous compression result in slower release times. Also, the elements have a natural lag time in their attack response, and a soft knee. This gives them a natural sound, but makes them not appropriate for capturing fast transients.
Vintage opto units usually had only two controls: gain reduction and gain. Turning up the gain-reduction results in lowering the threshold giving more compression. The gain control is make-up gain.
Good examples of opto compressers include the LA2A, Anthony DeMaria Labs, Joe Meek C2 and SC2.2, and the Millenia Media TCL2.
Contrary to a previous post on this thread, the 1176LN works on the FET (Field Effect Transistor) principle (not opto), which allows much faster attack and release times, but can be more prone to artifacts (pumping) and distortion if not set correctly.
To sum up the section on optos:
There is a sidechain consisting of an LED shining on a light-dependent resistor. As the volume gets louder the light gets brighter, creating a corresponding increase in compression of the audio signal. Because the LDR has an inherent "memory effect", it releases slower when the light is brighter or has been shining for a while. That means heavier or continuous compression result in slower release times. Also, the elements have a natural lag time in their attack response, and a soft knee. This gives them a natural sound, but makes them not appropriate for capturing fast transients.
Vintage opto units usually had only two controls: gain reduction and gain. Turning up the gain-reduction results in lowering the threshold giving more compression. The gain control is make-up gain.
Good examples of opto compressers include the LA2A, Anthony DeMaria Labs, Joe Meek C2 and SC2.2, and the Millenia Media TCL2.
Contrary to a previous post on this thread, the 1176LN works on the FET (Field Effect Transistor) principle (not opto), which allows much faster attack and release times, but can be more prone to artifacts (pumping) and distortion if not set correctly.
