I have a ProChannel Preset I created which has nothing in it but the (turned-off) EQ (since I don't think you can delete that).  I make sure that loads that by default on all channels in my starting template.  No noise problems.  I was getting weird noise intermittently recently, however, from a wifi range extender.

ahriakin@whisperbetweenworlds.com
Long time Sonar (and previous Cakewalk xx) user here, but obviously first post :). I had the exact same issue, eventually also tracked down to the Pro-channel.

Hi Derek. Welcome aboard so to speak. Can you clarify under what circumstances you're seeing the noise spectrum you posted?
 
The Prochannel by itself should not (and does not in my experience) generate any signal. So far this thread has established only that the PC76 U-type Compressor module generates quiescent noise with no input signal. But the spectrum I'm seeing is much different from the one you posted (I can post a screenshot later).
 
I just want to make sure you're really seeing the same issue, and not something else that needs to be investigated separately.
 
If it's just the PC76 that's causing concern, that's easily avoided and shouldn't scare anyone away from using the Prochannel in general.
 
 
 

tlw
That looks like emulated mains hum.

Quite a lot of plugins add fake mains hum because some of the "character" of the original hardware was the intermodulation it added between the audio signal and the electrical noise the circuit created. Waves often even give you the choice between mains hum at 50 or 60 Hz.

When I reviewed the Waves Aphex Aural Exciter I asked why they included noise in it. They said that in critical listening tests, when they blind A/Bed versions with and without noise, several engineers said the version without noise "didn't sound right." However, they had the good sense to make the noise switchable. I prefer it without the noise 

Anderton
I like puzzles, and I like testing things. So here's what I did, starting from a new project.
 

• Created a track with the ProChannel enabled, the PC-76 U-Type compressor set to the default position, and all outputs assigned to the master bus.
• Cloned this track 200 times (and found out Noel wasn't kidding about speed optimization...)

 
(...)

Hi Craig, would you repeat the same experiment with PC4K ?  I had  c. 16 tracks and somehow PC4K switched itself on without my knowledge. I heard strange noise when all echos were off and transport stopped. Quick investigation pointed to PC4K.

Kylotan
If it's not showing in a spectrum analyser and the peak value on the track isn't showing any signal then I wouldn't expect cloning the track to have an effect

 
Well, the key was your saying it was a very low-level signal that you could hear only if you added about 60 dB of gain. If something that's an inherent characteristic of the ProChannel or the PC-76 produces noise, then to eliminate the variable of whatever is adding the 60 dB of gain, it seemed logical to stack a couple hundred ProChannels in parallel. That would be equivalent to amplifying the signal by over 20 dB. Then there was the additional amplification of turning up all the faders, turning up all the input gains, turning up all the compressor outputs, etc. I would think if noise was being generated by the PC-76 or the ProChannel itself, any residual signal would become clearly audible under those circumstances but that's not what I experienced. As to it happening in only one channel, I assume that the code for all ProChannels and PC-76s is identical.
 
Obviously I'm not duplicating your exact setup because I don't know the details...for example, what's adding the 60 dB of gain, whether the transport is running or not, etc. But it seems the above would indicate that any noise is not from the ProChannel or the PC-76 by itself. However, I didn't get a chance to check with headphones although that introduces the variable of the headphone amp in the audio interface, and the audio interface itself will have a noise floor and the potential to pick up interference via the USB line. So to eliminate that variable, it would be best to try and stick solely to the SONAR environment, and try to create a situation where the noise registers at SONAR's output.
 

In the OP it's stated that it occurs only on tracks that have program material or previously had program material. The noise was inaudible sitting at -129db. Adding 80db of gain makes it audible. So it's a noise that becomes audible at -40db. In the OP it's something that happens with no effects. You talk about making it audible by adding an amp sim and a distortion pedal.
 
I think you're chasing ghosts. At -129db you must be getting to the limits of your audio interface and seeing artifacts created by its circuitry. Amp sims and OD pedals are real noisy and I can get hum way below -40db by using a high gain amp model. I can be a detail fanatic and have spent days trouble shooting hardware only to find out that test equipment was inserting more noise than the hardware being tested.
 
I would repeat the tests using different spectrum analysers to see if they agree on the findings. If you still get the problem I'd look into getting an AC line supply that was filtered, cleaned and regulated. This thread has me very curious and I'll be following to see how it resolves.

Razorwit
 a work-around might be to just drop in another module that's not doing anything after the PC76 to see if that helps.
 

Another would be to remove all but the EQ from the PC and set that as track and bus defaults. The OP does not use the PC so I would think this would be the preferred configuration.

scook

Razorwit
 a work-around might be to just drop in another module that's not doing anything after the PC76 to see if that helps.
 

Another would be to remove all but the EQ from the PC and set that as track and bus defaults. The OP does not use the PC so I would think this would be the preferred configuration.

None of this is a problem for me because I'm just going to switch PC off, once I find all the files where the Sonar bug helpfully switched it on for me. I'm just following up because there's another bug or dubious feature here that deserves investigation.

I was so curious that I picked up span to test my system. I can replicate the OP findings more or less. It is the output from the PC76. If you adjust the output gain or mix of the PC76 the signal in span changes. On my system the noise is at -156db when the PC76 is set normally. (0db gain and 50% mix) If I max the gain and set the mix to 100% I can get the signal up to -130db.
 
After doing all this I still don't see it as a problem because I can't hear it and have to go out of my way to see it. Unless I followed the instructions in this thread I wouldn't know about it. I wish the original equipment had specs this good. 

Klaus
I too can replicate what the OP sees.
However, the same happens when you use several other effects:
Waves SSL Channel Strip, API-2500, PuigTec EQP1A and every other plug-in with an "Analog", "Noise" or "Mains/Hum" - switch I tested so far will show a peak value on the track, if these switches are on.
The track goes back to complete silence if these "analog" settings are off.
 
Since the 1176 ProChannel module is modeled after analog hardware, the "noise" is probably part of the signal of the emulation.
 
IMHO not a bug, otherwise a lot of plug-ins would be buggy, too.

The adc can send small non-zero data to the pc due to inherent circuitry noise. But in the test the audio track does not appear to be set up to receive input from the audio interface. I agree that this is probably modeling noise.

FWIW, I believe this was introduced in J.
Here is an image of an audio track PC76 enabled in I.

and the same project on J

 
I don't have a spectrum for it, but I can repro this at -123
 

scook
FWIW, I believe this was introduced in J.
Here is an image of an audio track PC76 enabled in I.

and the same project on J

Steve, you are one amazing forum host. :-)

One last thing. The image above for SONAR Ipswich only looks that way because no audio had passed through the track. After setting the input to something other than NONE and setting it back, the image looks like J. SONAR I acts the same X3e. I suspect this noise is intended. Overloud does this in a couple of other plug-ins too. The only thing that has changed in SONAR J and newer is when the noise shows up.

Kylotan
Thanks for looking into this, everybody - at least it confirms that my computer isn't just being uniquely targeted with cosmic rays or something like that. :)

Well that's a separate issue... as are poltergeists.
 

scook
One last thing. The image above for SONAR Ipswich only looks that way because no audio had passed through the track. After setting the input to something other than NONE and setting it back, the image looks like J. SONAR I acts the same X3e. I suspect this noise is intended. Overloud does this in a couple of other plug-ins too. The only thing that has changed in SONAR J and newer is when the noise shows up.

Damn, you're good.
 
I looked at the help file for the PC-76 to see if it said what that meter screw adjustment did, and the second sentence said "This module is meticulously modelled after one of the most renowned and famous solid-state (F.E.T.) compressors that is used in professional studios and recordings." Based on what I've seen from other manufacturers, that usually includes the noise. As to why it would change with sample rates, well, it IS audio...