Do I need both red and white RCA cables?

[Hypersonic1]

I am about ready to capture some mono (how would I know?) VHS-C tapes. It seems like when I have the red and white plugged in, there is a little bit of a buzzing sound that is noticeable when no tape is playing. Is there an advantage to using both plugs?

I am using an Panasonic AG-1980 passed through a Panasonic DMR-ES15, and captured with a Diamond VC500.

[redwudz]

Depends if the mono audio is on both channels of the tape. You could get hum if the other stereo channel is empty on the tape.

If just on one, I have used a 'Y' connector to split a single channel output to two stereo input channels for capture.
If not, during editing, you may have you may have to add the one good audio track into a audio editor like the freeware Audacity and paste the audio into
both channels for output, then add it back to the video. Otherwise all your sound will be from one side of the room.

It's a lot easier to combine it during capture.

[Hypersonic1]

So there isn't any additional loss by using only one plug assuming the source is mono? I know I can just do a fill left or fill right in Adobe Premiere to have it output to both speakers.

What is the best way to determine if my tape source is mono? Also, should I pass the audio through the ES-15 like the video?

[redwudz]

If you view both channels, one above the other in your audio editor, it would be obvious if they are duplicated or mono.
I processed a couple of boxes of mixed VHS tapes last year, and a few were mono. Those were mostly tapes of old B&W movies.