How to monitor a mono signal in both headphones?

when recording into left/line-in

There is probably a simple answer to this, but its eluding me.

I lay down acoustic guitar tracks in mono, miked up via a preamp and into my soundcard line in, whilst monitoring everything through my headphones. Obviously as my guitar is going into the left channel on the soundcard, I can only hear it in the left headphone. I would much rather be able hear it in both headphones (but still recording in mono)

Other than getting a mixer and feeding the input to both channels is there any way to do this?

I don’t know what soundcard you have, but with mine (Audiophile), there is a pan control in the software mixing panel that came with the soundcard. Hope this helps.

You need a mono cable with a mono plug on the end that comes from the preamp and a stereo plug on the end that goes to the soundcard; the + part of the cable should be soldered to both + on the stereo plug.