I video'd footage with a mono mike so I only have one channel. The other has a bad hiss which I got rid of by using "Pan" slider. When I render I want that one channel to be audible on both speakers. If I choose "combine" then the hiss gets added. How do I render 1 channel to both channels albeit mono?
Don't use Combine - just use the channel you want, Left or Right.
I have done this AND have copied say the LEFT channel to a track below and used the PAN on each channel to make for some spread. That works.
But ideally if the HISS isn't too bad one can get some remedial results using Sony's Noise Redux.
But, here, just use the channel you want. Don't bother with panning-OUT the channel that you don't want - just select the channels you do want. Or have I missed something?
R Click that event and select Channels. Then select Right or Left only as desired.
Now that's fine for just an event however if you want to do it for a track then you need to apply an FX to the track or buss. Problem is Vegas doesn't come with such an FX so go get the free Stereo Tools from Kelly industries: