I have the CA-2A in the PC on a vocal track. With the CA-2A threshold and gain set to their defaults, the vocal is hitting the CA-2A too hard for my taste. I turn the level of the vocal track down but, it doesn't seem to affect how hard it's hitting the CA-2A. I even turned the level of the track completely off and it still doesn't affect the CA-2A.  I'm confused. Is the PC pre fader? Is there a signal flow diagram for Platinum somewhere? Am I just missing something here?

The PC can be either pre or post. To change, right click on the top of any PC module & select pre or post.
If your signal to the CA-2A is too high, lower the track gain.
  Happy Musicing!  

Here's a Cakewalk Blog article that might help...
http://blog.cakewalk.com/know-your-signal-flow/

--
Scott R. Garrigus - http://www.garrigus.com
* Cakewalk SONAR Video Tutorials: https://www.youtube.com/u...gus?sub_confirmation=1
* Author of the Cakewalk Sonar and Sony Sound Forge Power book series: http://garrigus.com/?PowerBooks
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* Publisher of the NewTechReview consumer tech newsletter: http://www.newtechreview.com/

The photo Pwal posted has always been the drawing board for me
In pro channel's default state its order is:
Input / Gain / PC / FX bin.
 
In your case, I believe you can use the Gain knob to achieve desired results.
The CA 2A has an input knob which can prevent the signal from overloading/slamming the compressor too hard.
The gain will also produce a similar response.

chuckebaby - where is the input knob? The gain knob is for make up gain. I suppose I could put the Tube plugin before the CA-2A and reduce the level coming into it that way.

Anonymungus!
The PC can be either pre or post. To change, right click on the top of any PC module & select pre or post.

I think this is actually wrong. The pre or post selection of the prochannel refers to it's position relative to the FX Bin, not the fader.

The track Input Gain is your answer. That is pre Pro Channel and will lower the signal going into it.

rodreb
I suppose I could put the Tube plugin before the CA-2A and reduce the level coming into it that way.

 
No need to, Use the tracks Gain knob within Sonar. This lowers the out going track signal (not the fader).
To be honest, I rarely if ever use gain knob in sonar unless I have a plug in that has no input which in the case of the CA2A I use the Gain knob to adjust the incoming signal that gets processed.
 
Some plug ins (older ones) don't have input controls, this is a perfect solution (using the tracks gain knob in Sonar)
 
I can totally understand where you are coming from as in our hey day, we ran a lot of post gain staging where the fader would increase signal of the plug in (effect). The way Sonar defaults, raising a fader doesn't increase the amount of signal that goes to the FX, it is kept a constant, Using the Tracks gain knob increases signal to the FX.
 
A bit bizarre but when I use Sonar I don't see an analog desk, I see someone trying to copy an analog console but instead created a digital audio console... LOL.

RSMCGUITAR
The pre or post selection of the prochannel refers to it's position relative to the FX Bin, not the fader.

I believe you are correct my friend.
 
Pro channel in default PRE:
Input - Gain - ProCh - FX
 
Pro channel in POST:
Input - Gain - FX - ProCh
 
As can be seen in PWAL's signal flow chart, Pre and Post Sends are the only thing a fader can manipulate.