flatfinger said:
could you give us a take on the opto-compressor, and what the advantages are? I think that they are noted to have the behavior of having a longer release it the above thresehold transient was stronger. The VCA is the most linear and more like what you described above , right?
My understanding is that that depends entirely upon the design of the opto curcuit. Older light-bulb-based opto compressors like the original LA2A were known for slow release characheristics like I described in my original post. Newer opto circuits that use integrated LED/photoresistor packages can act much faster and more linearly like a VCA.
What complicates that even more is that many newer LED opto compressors are purposely designed with various schemes (every manufacturer has a different idea, it seems) meant to mimic bulb-opto characteristics or otherwise add other coloration to make the release characteristics less or more VCA- or opto- or tube-like, depending upon the desire of the manufacturer.
For these reasons I'd hesitate on making a blanket statement about opto release characteristics.
You might want to take a look at
this article for a little more detail on the subject of opto compression.
flatfinger said:
P.S. still looking for your db standardization chart for this side of the pond!!
Yeah, I meant to have it done by now, along with another new feature on the website, but frankly a lot of recent family health issues have been sucking up more of my free time than I had planned. That chart is about 2/3rds of the way done, and it is still coming. Just give me a chance to slog through some more important life matters first
.
gabereding said:
Then the gain reduction would be going from 3db to 18.5db. That is not exactly acceptable, even if over the release period the gain reduction progressed linearly from 18.5db to 0.
I don't know. That seems to be the way it would work were that the case.
Which is why proper release time settings to avoid a breathing effect is important.
Doing it by a set amount of DB makes even less sense to me. The strength of the transient, not the gain reuction ratio, would determine the amount of post-threshold compression. It would require using a linear gain control circuit seperate from the compressor circuit. In other words, once dropping below the threshold, no longer use a ratio, but use a set amount of attenuation. Not to mention a way to automatically switch between them when that threshold point is reached.
Remember gain reduction control in a compressor is done by applying an input-to-output ratio, not my setting a number of dBs. When the threshold is crossed for longer than the attack time, the compressor kicks in at a set reduction ratio. Period. That reduction ratio is appied throughout. The amount of dB reduction is not a fixed value, but rather dependant upon the input voltage of the waveform itself. That remains as true past the initial trigger transient as it does at the trigger itself.
Remember, waveforms are complex entities and not simple periodic waves. Even while the wave is riding above the threshold, there are lower volume "bumps" on the louder stuff that are compressed as well, even though the bumps themselves are smaller tan the threshold setting. If I have a snare track that has some hi hat bleed on it, it'll be the snare hit that triggers the compressor, but the hat sound will get compressed also, even though the hat bleed itself is of lower volume than the threshold setting.
Once the threshold has been breached, it's like pulling a trigger and holding it open until you release. The threshold is just a trigger. But once the trigger is uplled, everything is shot buy the same amount. But the same amount means by the same ratio, not by a set number of decibels. At least that's how I understand it.
G.
