Excuse my ignorance and I'm a little embarrassed to ask that but I have a doubt. In the pro-c2 compressor I have a 30ms attack set but in the pspfet there is only up to 10. Why is this? Are there compressors with another type of time measurement?

 

Different compressors have different setting ranges depending on who makes them, their intentions, if a plugin is modeling hardware or not etc.
FET style compressors usually will have a faster attack characteristic / be used for fast, aggressive compression because of the characteristics of analog FET based hardware.
Though sometimes compressors will not tell you the ms amount of attack and release to encourage you to listen instead of setting nice numbers.
If you want to know more precisely how the knobs affect timing, check the plugins in PluginDoctor.
Note, that the envelope generators for the compression time curves may differ between compressors (that's design based).

I hope this could help.

 

Very good explanation

 

I'd like to add: Unfortunately most plugin designers do not take the values vs effect as serious as they should.
So lets say you have two very basic bread and butter stock compressors and lets say they're both of bigger brands like Avid and Steinberg -
you would't believe how different the same settings in both compressors sound.
And I'm not talking fancy stuff with valves or anything. I'm talking about the most basic threshold/attack/release/hold variants.
In my opionion, as this is not rocket science, entering the same values should lead to very similiar results.
But thats not what it does.

 

On top of all this, these numbers do not represent the actual attack and release times in almost all cases, and they tell nothing about attack and release curves anyways, which are more important for the sound than the time. I'd say these labels would've been better off as percentages.
Don't fret about milliseconds or tying release time to BPM. Train your ear and go with it.

 

Yes, a stock compressor should actually give you the attack and release times that the parameters say, but there are so many other factors that influence the sound of a compressor.

Different compressor plugins can have wildly different attack & release curves. They can either have exponential curves, S-curves, more vintage/analog-esque curves, or (rarely) completely linear curves. Attack & release can also be coupled with each other to different degrees. This is just the differences that the attack & release envelopes between different compressors can have, you also have many different parameters for threshold, ratio, detector circuit, knee, timing, and peak/RMS. Since there are no real standards for how a "perfect stock compressor" should behave, they all sound different.

The most important thing in a stock compressor (IMO is) that it it's fairly versatile, clean and has all of the most important features in compressor: adjustable input/output gain, wet/dry, threshold, ratio, attack & release, knee size, RMS size and preferably some kind of lookahead.

 

As the others already said, for pure digital comps the values should be correct, in practice, they are not exactly the same among themselves and for analogue emulations the dialed in values are more of a suggestion. Neither the times, nor the ratio or the threshold are what they're really doing. In one case I've found a difference of a factor of 30 in the release time!