The old forum had posts describing how to do that, but there’s no search function there any more 
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The workaround, I THINK, had something to do with a Mix 6-2 plug in … ??? Or a Voxengo plug??? …
Not sure why I can’t just take my stereo signals and make them mono by using the stereo dual panners panned centrally, but that wasn’t a good idea, as I remember people said back then. Would that be because the panning laws weren’t set up for that?
Thanks -
Yes, either via a 3rd-party plugin, but, as you have already written, via the included Mix6To2 (in the “Surround” VST subfolder). I can’t remember if there’s a supplied “mono” preset, but just set all its L and R faders to -6 db.
Couldn’t you just export back to Cubase with a mono export? Or, if I remember correctly, I think I got mono by putting a stereo part on a mono track.
I’ll look into it, vic france. But the name being 6-2 … it didn’t make me think of making it do “2-1”!
BTW - is that dual stereo panner idea I mentioned above an OK way to do it?
Thanks -
Yes (the default Pan Law should be o.k.) but it isn’t as quick as saving your default template with the Mix6To2 plugin inserted, loaded with the appropriate setting, but simply switched off (i.e. the plugin switch is your instant “Mono” button 
)
Cool! And thanks for the workflow efficiency reminder!
alexis, one way to search the old forums is Google…
site:cubase.net no mono button (or any other keywords!)
Yes, thanks for the tip there Scab Pickens!
Doing just that lead me to a gearslutz forum where someone said just take the left most 4 controls on Mix6to2, drop them to -6dB each, and voila, there it is. I tried that, and it does seem to work!
Though I’m not exactly sure what is being done here …
This Mix6to2 plug-in just seems like black magic to me, somehow … it seems to work in collapsing my stereo to mono, but I have no earthly idea how … a little help please!
Thanks! 
The Mix6To2 plugin doesn’t have independent panning for each incoming channel. Instead, each incoming channel has separate level faders, feeding the left and right of the Mix6To2’s stereo output, respectively (or, in the case of a 5.1 surround channel, there’d be 6 faders per channel). So that amounts to a “balance” control, really.
If, in the stereo version, you just had the Left fader up (at 0db) on the “L” section, and just the Right fader up (at 0db) on the “R” section, then the incoming stereo would just pass through unchanged.
So, for obtaining mono from the incoming stereo, the Left input from the channel is routed, in equal proportions, to both faders of the section of the Mix6To2 marked “L”, and the Right input from the channel is routed to both faders of the section marked “R”. The two faders of the L section, and the two faders of the R section are all turned down to -6db, to satisfy the perceived pan law.
Alexis, I want to respectfully encourage you to think about getting Cubase 6. No I don’t work for Steinberg, but I was on SX3 for a while, and I did not care for Cubase 4 when it came out. However Cubase 5 (which I am still on) made so many improvements, not to mention the mono and dim buttons in the “Control Room” to create different mixes for people tracking with headphones. Yamaha stepped in and gave Cubase improved bread and butter effects, work flow, that Cubase 5 and 6, are much better programs. I did not jump to 6 yet, since I am still enjoying 5 and the improvements that it offers over SX3.
I’m with you on this one, Glen - just saving pennies for the day. I pre-ordered that Streamworks C6 video (should be out by today) so I can study up before I actually receive C6. I do have to say, having gone through what seems like the wars in SX3 (all that stuff it took to get to the final stable version), I’m a little hesitant to go off into a new set up, but not nearly as hesitant as I am excited!
Thanks -
I use DFX Monomaker ( http://destroyfx.smartelectronix.com/extras/ )
It is freeware.