how to rip a VCD with 2 audio channels

Some people may have other methods, but this is how I would do it:

Use VCDGear or ISOBuster to extract the MPEG out of the VCD - info here

Then open the MPEG in virtualdub and save the audio out to a WAV file - info here

Then open the WAV in Goldwave or audacity (or any audio editor that shows you separate channels). Then you should be able to remove one channel, and then duplicate the channel you wish to keep to replace it, giving you a double mono / quasi-stereo audio file. Save this out to a new WAV.

Convert the WAV to 224kbps MP2 using besweet or ffmpeggui. Demux the MPEG using TMPGEnc's MPEG tools, then remux the video stream with the new MP2 audio file.

Done

If the channel you want to keep is the left channel, go to Edit > Channel > Left, then go to Edit > Copy, then go to Edit > channel > Right, then go to Edit > Paste at ... > Beginning. This should then replicate the one channel across both channels.