Brainworks Stereo Maker Plugin works best for me

http://en.wikipedia.org/wiki/Duophonic
 
I believe I have the tools to do this ^^

Konrad, there are 3 ways you can do this. Probably more but I'll give you all 3.
 
1. Put a delay on the track. Use a Sonitus if you want. Set the left side as low as possible on the delay time.
 
Set the right side to say, 30 ms for starters.
Set the feedback in both spots to 0
Crossfeed to 0
Mix in both spots to 100 all the way up
 
Don't worry about anything else in the plug for now. You CAN mess with the other things, but what you have above will give you a stereo imaging type sound that will be controllable. If you want the sound to be a bit more loose set that 30 ms to a bigger number. A smaller number will tighten it up.
 
2. Channel tools will do this too but you don't have the same options you would with the Sonitus delay. Choose the "increased width" preset in channel tools.
 
3. Clone the track so you have 2 of the same track.
 
Pan one hard left, the other hard right.
Hi-lite the right panned track. 
Go to process, then slide and choose ticks.
Choose a number. The ticks are sort of like millisecs. You'll notice that after 10 ticks, the file will get looser. So pick like 15 or 20.
 
What we did here is the same as what we did with the delay in choice 1. However, the difference here is, you now have eq control for both of these tracks. The slight eq adjustment you'd make here on both tracks will give you even more control as they will not only be delayed, but eq'd a bit different from each other.
 
Hope that helps!
 
Barry: Would you believe I still use those Qsound plugs to this day? I bought the disc years ago and got to be friends with someone at the company named Kennedy. He hooked me up with updates of the software and it works in Sonar X3 as a DX plug. There were 3 different plugs in that package. 2 of them work, (Qsys and QXpander) the 3rd will not. But it's ok, the one that doesn't work wasn't one I used anyway so I just disabled it in my plug menu. :) If you still have your disc and can install, you can definitely use them. I'm using Win 7 x64 and they installed fine but I had to use compatibility mode to get them to install. They are installed on 2 machines with the same OS...so you can make them work. :)
 
-Danny

I believe Vintage Channel had a  preset for that. Is it still with X3, I don't know.

Thanks, Danny.  I hope my result will sound better than the old Capitol fake stereo.   I just listened to a "Duophonic" version of The Beatles' "I Feel Fine" and it sounds horrible: the mono version is 10x better.
 
Apparently, duophonic was delay, hi-pass on one side and low-pass on the other, plus some stereo reverb.  I had incorrectly thought there was some comb-filtering involved, but I guess it was simpler than that.
 
I am still interested in some fake stereo for a particular song on my upcoming album Kellis Park.  The song in question is sort of a neo-hippie thing.
 
Take care.

No problem Konrad....you should be able to nail the sound you're looking for using those methods I told you about. And...if you really want to make it cool, you can use the tape sim plug in Sonar X3 on the bus and then try this thing: http://izotope.com/products/audio/vinyl/index.asp 
 
It's free and I've used it several times for making things sound a bit more vinyl. I know you're probably not looking for anything like that, but it's still a cool plug to add to the arsenal. :) Good luck with everything man...would love to hear the track after you're done with it. :)
 
-Danny 

Waves PS-22 does exactly that and has some other tweaks to boot (such as only stereoizing above a certain frequency). 


Just wait till the gold bundle is on sale at around $400, then buy it from PluginDiscounts.com for a lot less than that. Interestingly, Logic includes a plugin of this nature but without the extra features.

I love vinyl. One of my fav plugs

Duplicate

You can draw a signwave EQ adjustment on the left channel and invert it on the right channel. If you hold control you can double the length of the snap setting so you can get waves that fluctuate every 2 measures. Set your temp slow so the measures last longer.
 
This will give you subtle and slowly altering eq changes. Follow Craig Anderton's guitar stereo-izer method for widening a guitar track. Use EQ Automation to alternate channels for the eq differences over time.