I am having problems recording into my laptop. Here's my setup:
Guitar into Vox Pathfinder 15R Amp line-out into PC audio, via 1/4"-1/8" adapter. Recording with Audacity on laptop.
Unfortunately there's a considerable amount of crackling on the recording. Here's a sample bit, please excuse the horrible playing. Where can I start to look for the crackle in the background? Is it my playing?
First off, put your ear right up to the speaker on your Pathfinder (while you're not playing!) and make sure it's not coming out of there. I doubt it is, but it's worth it to double check.
After that, the most likely explanation (IMHO) is computer power supply noise leaking into the sound card through the ground plane. It's possible that recording on battery power can eliminate this, so try that. The best workaround is to just always record on battery power and fully charge it before recording.
It could also be a ground loop between the Pathfinder and the laptop. If you haven't read about those before, basically the power supplies of the two different devices could have different "0" voltages (called ground). The "0" is in quotes because it's rarely exactly 0, even though it's treated like 0 volts in the circuits. When they don't match perfectly, noise flows through the cable connecting the two devices and gets into your audio. If this is the case, recording on battery should also be a workaround for this problem.
Finally, it could just be a low quality line in. Well, all line ins on computers are low quality, relatively speaking. The only fix for this is to get an external audio interface. If you can swing it, this would be the best solution for all the possible causes of this problem. The best sound quality you can get would be a microphone right up to the speaker of the Pathfinder with the signal going along an XLR cable to an external interface (USB is probably your best option) and then into the computer. You can get all of that (mic, computer, cable, mic stand) for less than USD 300, depending on your exact choices. That would eliminate any possible ground loops, bypass the low quality line in, and even get you some of that speaker sound and background room tone that should add a little life to the sound. Plus you can use the mic to record almost anything else.
I started recording my own songs using your method, and I collected some useful tips.
First, be sure to use the Amp with a wall socket that provide you with a ground connection. Here in Europe would be a Schuko type plug. It happened to me that if I didn't connect my amp to ground, I would get very strange background sounds that change as I touch the guitar in the different metal parts, because I was providing ground through myself.
Second, use a Line In/Mic plug that is as far as possible from an output from your card. I initially used a frontal connection that was close to the output, and I got bleeding sound from output again into the input. I later used a rear Line In connection that solved the issue.
One last tip, be sure to check amp's output levels and/or pc's input levels, it could be some clipping. Also try to use some other recording program, or listen through Windows own 'Listen to this input' option, to discard Audacity's fault.
And as Todd told you, an external interface would be the very best solution, and I extremely recommend it. What I disagree with is that I prefer to record guitars connecting them directly to Audio Interfaces, because you don't need to know miking techniques, and you don't get any external noise. You could even feed that Line Level signal from your amp into the Interface, if you really like your amp's sound.
FYI, I own a Line6 POD Studio UX1 that is not expensive (120$ at Amazon), and I am extremely happy with the perfect audio it records, plus it provides high quality outputs for your speakers/monitors. I even do live gigs with it. I love it.
