Not a problem, it’ll be fine. Just remember 1/4" stereo headphone output to 1/4" balanced mono input!
So if you put a normal signal lead (unbal) into the headphone socket all the way, it’ll short out one side of the headphone amp!
It’s alright to put an unbal 1/4 into the soundcards input it’ll just unbalance it.
You can bodge the headphone plug by not putting it all the way in into the socket, so the tip only engages the first indent, thus tapping only one side without shorting the other.
Otherwise you would need to wire a suitable jack using a stereo plug wired for one side of the headphone output to a mono (unbal) jack for the pre input.
Right now I would be using a generic guitar cable to connect the guitar to the amplifier, and a 10 ft Hosa Pro Cable to connect amp and interface. I’m guessing most guitar cables are unbalanced and of course mono, correct?
As far as y cables, I do have one of this which is stereo in, stereo out.
So what would I need for this to work? Right now I’m hearing three guitar cables (one for guitar to amp and two for the interface) and a y cable. Do they make these for combining mono signals, or will the one above work fine for this?
But I wouldn’t bother. Usually just running guitar cable from headphone output to audio interface works well. Yes, it shorts the right channel of you amp’s headphone output, but I haven’t yet met a headphone amp, which can’t handle a short-circuit.
OTOH, why do you want to record signal from headphone out of your amp? Usually big part of the guitar sound is generated by the speaker. That’s why we usually put a microhone in the front of the speaker.
I like to perform without starting up my DAW every time, in fact you don’t even have to log on. Being that the amp is my guitarist friend’s, I don’t think he’ll like that idea…