I am a huge fan of the Channel Tools "Increase Width" preset (as suggested above) for the following reason:
Bring up the preset, and on the lower right there are sliders for width of left and right.  You can make it very wide, more narrow, or you can have it slightly lean to one side or the other.
 
I am remixing a bunch of my old analog 4-track stuff, and most of it was "four mono channels", so I am using that preset (varied by track of course) in a ton of these remixes.  Working great here.
 
Best,
Ed
 
PS, for the effect to work at all, the tracks interleave button must be set to stereo not mono.  Make sure it looks like this: >>><<< (not like this: >>>) or you won't "hear" the effect at all.

In addition to panning the original and the clone hard left and right with some small amount of delay, try also detuning the two tracks by a small amount, one up and one down.  This technique may very well be automated in some plugins but I'm unaware which ones.  'Image spreading' I think it's called.

If mono-compatibility is important to you, be wary of the Haas effect techniques (delaying one channel slightly) as it will likely produce unwanted comb filitering when collapsed to mono.
 
There's a stunningly good effect made by MeldaProductions that uses EQ differences only (or optionally also delay processing) called MStereoSpread.  I believe that Waves has a plug that uses a similar technique.  I have MStereoSpread and it's brilliant (I have no first hand experience with the Waves offering).  However, MStereoSpread is intended to make mono signals stereo, which is a bit different than what you've stated you're looking for.

Nugen Audio is on the right track. It's an easy thing to do manually, but the plug makes it much faster. Here's what I do:

1) Clone the track twice as mentioned earlier, giving you three tracks. 
2) Leave one centered and pan the other two hard left and right. 
3) Click the Phase button on one of the panned tracks and pull them back in from hard-left and hard-right until they sound about how you want. 
4) On the panned channels, put a high-pass filter in with a non-drastic slope between, say 300-500Hz.
5) On the centered channel, put an EQ with a gradual sloped Low-Pass of about 200-400 Hz (where you feel is right), so that centralized bass frequencies stay centered. 
6) Feel free to experiment with the EQ filters and panning, until you get what you're looking for. Don't be afraid to bring up the "filtered-out" frequencies on the centered channel if you think the higher frequencies missing there.
7) After doing this, you can play with delays, or echo tools, not to mention the free Flux STTool from Flux Home. 

Best of luck!!

Hi,

Craig Anderton had in one of hs video's an interesting solution for acoustic guitar.
He made two clones of the mono acoustic guitar.
Panned the orgininal in the center.
Panned one clone to the left with a lowpass filter
Panned the other clone to the right with a highpass filter.
This broadens the sound of the acoustic guitar.

This is a very simple technique.

tomixornot

Just came across this

http://www.musicradar.com...e-world-today-277953/3

Have not tried yet..

The plug-in's name is Upstereo (For those who haven't clicked the link).

I downloaded it and checked it out when you posted the link.

Oh my. It's a great VST.

The 'Air' control is excellent.

It seems to do it's best when you place it before a reverb.

It's a 32bit VST, but I've been using it for hours without a hiccup in X2-64bit which is a lot more than I can say for most 32bit VST's I've tried running through Bitbridge.

Bub

tomixornot

Just came across this

http://www.musicradar.com...e-world-today-277953/3

Have not tried yet..

The plug-in's name is Upstereo (For those who haven't clicked the link).

I downloaded it and checked it out when you posted the link.

Oh my. It's a great VST.

The 'Air' control is excellent.

It seems to do it's best when you place it before a reverb.

It's a 32bit VST, but I've been using it for hours without a hiccup in X2-64bit which is a lot more than I can say for most 32bit VST's I've tried running through Bitbridge.

I thought this plugin was designed to widen the stereo image of a stereo signal (like Ozone's Stereo Image). No?
Does it really convert a mono signal into stereo?

Shambler


You could try http://www.voxengo.com/product/stereotouch/

I tried this yesterday. I does a good job and it's free! 
Although it uses delay, I don't hear the undesirable "one side (that you hear first) sounds louder first and then the other side grows louder later" effect of the simple "delaying one channel slightly" technique (I haven't tried it in a mix so I can't tell for sure, though).

Thanks for posting the link.

@Bub: Sorry, I forgot the OP wasn't just looking for mono->stereo conversion. 

Eq the hard left and right tracks to create stereo image placement...say high pass on one side and low pass on the other to match where the high notes and low notes live in the real world  

I am not saying that this would not work to "broaden" the effect, but I am pretty confused about how sound in the real world sorts itself out low to high aligned right to left. The guitar is a mono instrument for all practical purposes, and no one can distinguish the different origination of high vs low strings separated by a couple of inches in an acoustic and not at all in a magnetic guitar. At best one could postulate that in a very asymmetric reflective/absorptive audio space there would be some asymmetry in the frequency mix of reflections coming from different directions. To the extent that this works it is not because it represents an acoustic model of the real world.

Two things I've used to create some nice tones......
     1) ADT (Auto-Double-Tracking) - http://www.kvraudio.com/product/adt_by_vacuumsound
         Does a really nice job of recreating the clone-pan-and-nudge technique but also has a few other settings (wow and flutter) to give the sound a little more life than simply delay.

     and,



     2) The DSP-Fx Chorus' Guitar Quadruple setting (http://www.dspfx.com).  I bought these quite a while ago and they are still quite relevant sound-wise albeit they are DX plugs.  These were included in Sonar (don't remember which version they debuted) with different interfaces.  The sonar version is FX-Chorus.  This plug sounds really great for widening/adding life to both stereo and mono guitar and rhodes tracks.


Best,
guitardood


EDIT: Also, +1 for the Voxengo StereoTouch