the beauty of opto-electrical compression

PhotoresistorOpposed to VCA, Variable-Mu or FET based approaches, opto-electrical compression takes advantage of using a light-sensitive resistor and a small light emitter (a LED or electroluminescent panel) to obtain a gain reduction voltage in the sidechain path. This technique is well-known to add some smoother gain riding characteristics to the signal because of the specific attack and release response which comes from the inertia and inherent memory effect of the photoresistor element.

Program dependency

Typical classic opto-electrical circuit designs do have a significant and highly program dependent impact on the processed sound and this comes mainly from three factors:

  1. The adaptive release time characteristic which gets faster at higher compression activity and can be fairly long when leaving the compressors duty cycle.
  2. The specific compression transfer curve which features soft-knee characteristics by nature and limits the dynamic range.
  3. The frequency dependency and non-linearities which impacts the actual behaviour of things like the compression transfer curve.
OptoTransferCurves

Experimental frequency dependent "opto" transfer curves

In addition, opto elements do have an inherent lag time in their attack response which is typically not fast enough to catch short transients but adds up to an overall smooth gain riding impression.

Light and shadow

Opto compression really shines on overall adaptive and smooth gain riding purposes such as for vocals and solo instrument performances, whereas faced with rather complex program material it can easily tend to sound rather quirky. This might be the reason why it is typically not used that often on the mix-bus or if so then just with few amounts of gain reduction.

In digital implementations where the opto element effects are modelled in an explicit fashion this kind of weirdness can be avoided and both, frequency dependency and non-linearities can be applied in a way to better support full program material.

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Comments

  1. Please, opto compressor…

    LA2A is cuming..?

  2. smell like teen COMPRESOR………..

  3. Yeah! Give us that Krautplugin! ;-) Make it as easy to use as the Teletronix!
    Still voted for ferric!

  4. I think I know what he’s developing next! :D I can hardly wait! Ferric was my number one.

  5. I’ve been wanting something like this from Bootsy. There is no excellent LA-2A style compressor out there that is high quality and for a great price (or free). The only quality Opto compressor I know for a good price is the IK Multimedia Tracks Opto Compressor single. But I’m hoping this is more LA-2A-ish with some subtle emulation.

  6. Honestly, I bet it’s going to be “better” than an LA-2A :)

  7. Bootsie, maybe you can look onto infamous Lexicon PCM41 opto limiter, so Andy Wallace trick really hits the masses? =)))

  8. AT LAST BOOTSY MAKES A MOVE.

    JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK, JOE MEEK.

    The successor to Sacha’s Phishphones could be near.

    GO BOOTSY.

Trackbacks

  1. [...] entirely new build opto-electric style compression unit. As already written in the article “the beauty of opto-electrical compression“ this type of  circuit designs do have a significant and highly program dependent behaviour [...]

  2. [...] the beauty of opto-electrical compression Share this:Like this:LikeBe the first to like this post. Filed Under: Feature, TechTalk Tagged With: copmressor, downward, expander, gate, parallel, soft-knee, threshold, transfer curve, transient response, upward « public betas for NastyDLA and VCS, BootEQ, Density and Ferric updates available for BootEQmkII, DensitymkII, FerricTDS and NastyVCS » [...]

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