Fabfilter Pro-C 3

[musicman691]

FabFilter didn’t screw the pooch here, and bmanic’s understanding is solid. If it’s behaving differently than other “vari-mu” plugins, that’s likely because you’re comparing circuit emulations to an algorithm that’s adapting vari-mu behaviour inside a modern control framework.

This is exactly it! Said with much better and more intelligent wording than I could ever come up with.

FabFilter squeezed an exact and true Vari-Mu system on to conventional controls and it takes some time to learn the ins and outs of that system.

Easy mode is this: just dump hot input levels into the plugin either via the Side Chain level control or the main in/out level knobs. Then threshold and ratio will be at easy to operate nominal settings. If you need to compare between algorithms, use the A/B slots for that.

Thanks for the explanations. It would be great if stuff like this was put into the manual or help file. Elsewise you wouldn't have people wondering what's going on. A simple few lines are all that's needed. How hard would that be to do? I mean FF does some elegant programming but why can't that extend to the documentation?

While we're on this particular little bit it would seem to me that boosting the input level would be better than boosting the sidechain level. If you do the latter wouldn't one have to make changes to the eq nodes level-wise? As to levels I generally don't fuss about dbfs but measure in K12 or K14 when I have the option to do so.

[musicman691]

Thought I'd start a separate message chain here and ask: for all the emulations in C3 I wonder why there's no 1176 in there? At least I can't find it.

[E_Anderson]

While we're on this particular little bit it would seem to me that boosting the input level would be better than boosting the sidechain level. If you do the latter wouldn't one have to make changes to the eq nodes level-wise?

What would prompt messing with the nodes? Increasing the sidechain gain is not entirely dissimilar to increasing input gain and lowering output gain simultaneously, for preservation of any algorithm-specific threshold behavior.

[musicman691]

I don't know - that's why I asked.

[bmanic]

FabFilter didn’t screw the pooch here, and bmanic’s understanding is solid. If it’s behaving differently than other “vari-mu” plugins, that’s likely because you’re comparing circuit emulations to an algorithm that’s adapting vari-mu behaviour inside a modern control framework.

This is exactly it! Said with much better and more intelligent wording than I could ever come up with.

FabFilter squeezed an exact and true Vari-Mu system on to conventional controls and it takes some time to learn the ins and outs of that system.

Easy mode is this: just dump hot input levels into the plugin either via the Side Chain level control or the main in/out level knobs. Then threshold and ratio will be at easy to operate nominal settings. If you need to compare between algorithms, use the A/B slots for that.

Thanks for the explanations. It would be great if stuff like this was put into the manual or help file. Elsewise you wouldn't have people wondering what's going on. A simple few lines are all that's needed. How hard would that be to do? I mean FF does some elegant programming but why can't that extend to the documentation?

You are absolutely 100% correct. It really needs to be in the help file. I'll try to persuade the guys over at FabFilter to perhaps include more in-depth descriptions and usage tips for some of the algorithms. I'll also try to see if the auto-gain can be improved somehow (probably with some kind of more common threshold for it's calculation, like -12dBFS or thereabouts). In general, I'm sure the whole plugin can be improved still quite a bit further. My personal pet peeve is the lack of small arrow buttons for changing the algorithms and the character modes. I'd also love a way to quickly turn on/off the character thing.

Hopefully we'll get some updates on this in the near future once they are all back from NAMM.

Cheers!
bM

[kraster]

[...] note that these two options do not create the same results. Using the main input/output controls yield the same result as if your audio source was coming into the plugin at a higher level. Adjusting the Side Chain Level does something different [...]

[...] the Side Chain Level control does NOT equal the main INPUT + OUTPUT gain controls. If you boost the side chain level with +10dB and setup another identical instance but instead boost the INPUT control with +10dB (and compensate on the output with -10dB) you do not get the same results. They do not null.. not even close!

Would it be possible to get perhaps a qualitative if not a technical description of the difference?

The difference between boosting sidechain vs input on a Vari mu comes down to the fact that there is no discrete gain reduction stage. The tube itself IS the gain control. The input signal is operating directly on the plate current of the tube. By contrast, a VCA compressor applies gain reduction in a separate gain reduction element acting on an already-amplified signal.

So boosting the input in a Vari Mu doesn't just increase gain reduction but also shifts the tube’s bias, alters the knee and time constant behaviour, and adds level dependent harmonics. The best way to look at it is that input is both boosting the input into the tube and the control signal controlling the gain reduction. If you boosted the input signal alone (ie. no sidechain) into the tube get you that classic silky, thick tube character.

In fact one of the most common uses for boxes like the Manley Vari Mu is as colour boxes with no gain reduction.

Boosting the sidechain, on the other hand is only operating on control voltage and more or less leaves the tubes character alone. This increases reduction at the same signal level while largely preserving the tube’s operating point, knee, and harmonics resulting in a more linear, cleaner result.

One way of looking at it is that input signal changes the control AND behaviour/character of the sound whereas sidechain mainly changes only the control.

[NAD]

The difference between boosting sidechain vs input on a Vari mu comes down to the fact that there is no discrete gain reduction stage. The tube itself IS the gain control. The input signal is operating directly on the plate current of the tube. By contrast, a VCA compressor applies gain reduction in a separate gain reduction element acting on an already-amplified signal.

So boosting the input in a Vari Mu doesn't just increase gain reduction but also shifts the tube’s bias, alters the knee and time constant behaviour, and adds level dependent harmonics. The best way to look at it is that input is both boosting the input into the tube and the control signal controlling the gain reduction. If you boosted the input signal alone (ie. no sidechain) into the tube get you that classic silky, thick tube character.

In fact one of the most common uses for boxes like the Manley Vari Mu is as colour boxes with no gain reduction.

Boosting the sidechain, on the other hand is only operating on control voltage and more or less leaves the tubes character alone. This increases reduction at the same signal level while largely preserving the tube’s operating point, knee, and harmonics resulting in a more linear, cleaner result.

One way of looking at it is that input signal changes the control AND behaviour/character of the sound whereas sidechain mainly changes only the control.

That makes perfect sense, thank you!

[Calagan]

@kraster : thanks a lot for the detailed and precise explanation. But how did FabFilter implemented this behavior in Pro-C, where I believe there's no tube saturation coming from raising the input gain in the vari-mu emulation ?
Did they emulated the change associated with going further in the non-linear zone of the tube when raising the input gain, but without the sound of the saturation (that you can add with the additionnal parameter shared by all the models) ?

(I don't own neither have the demo of the Pro-C 3 - I'm interested because I could fail and try/buy it later)

[dastewart]

You are absolutely 100% correct. It really needs to be in the help file. I'll try to persuade the guys over at FabFilter to perhaps include more in-depth descriptions and usage tips for some of the algorithms.

---snip---

Cheers!
bM

This x100! It's the biggest issue I have with the whole Pro-C line. it is a fabulously flexible compressor but with all that flexibility (even more so with Pro C3) then I think most people could really do with a little help about what's under the hood of the algorithms and how the other controls impact them.

Not everybody is a compressor nerd who wants to go on a lengthy voyage of discovery to unpack the mysterious held within!