The crackling might be wrong sample setting.
Dear Friend.
The crackling MIGHT be latency. Just incase the term's new to you, that means the amount of time the signal takes to get from your instrument - guitar or whatever - throuigh the computer to the speakers. You can think of it like a piece of string, believe it or (k)not! If the sound was a single piece of string tied between your guitar and the speakers, you'd have one single, perfect connection - no crackles. If there were lots of little pieces of string between guitar and speakers, t he s ou n d wou l d lo o k some t hi ng li ke th is s en ten ce - all bits'n'gaps. The 'crackles' are the gaps between the sounds.
To check-out whether or not this IS the case, first make sure you've got ASIO selected. ASIO stands for Audio Stream Input Output and is a universal driver specifically designed to have a tiny CPU footprint - in English, that means it doesn't bother the processor much. Which, hopefully, means no gaps, so no crackles. That's the theory, anyway. Check your software's PREFERENCES to see if ASIO's selected. If you choose it and no sound at all comes out, you might need to select your soundcard's driver software - it usually shows up on START/Control Panel - and p*ss about with the settings there until you find out which ones work with Asio! Also, try different sample settings. There'll be a buffer on your sound card's settings somewhere saying 'samples'. On my M-Audio Audiophile 2496, it's in the Hardware Settings tab. Higher isn't necessarily better, it's just which one works best with the software you're using. It's suckit'n'see time, folks! If you find a setting which makes the crackles vanish, you might not need to read any more of this admittedly lengthy post.
Next thing to test, or you could try this first before the ASIO business (if you've already spent a couple hours sorting out ASIO and THEN you read this paragraph, just bung the guitar at me!) is if you get any pops/crackles just playing the guitar directly through the computer. Just - I expect you've done this already, but bear with me - plug guitar into the computer, have the soundcard outputs connected to the amps, make sure the soundcard's sliders are turned up and just play a couple of chords. I don't play an instrument - I'm disabled - but I've tried playing a tape deck through my computer by just doing that and it works with the tape deck, so it should work with the guitar.
If you hear the sounds with no pops/crackles, you're in business. Because you can download a piece of free software - it's legit. free - called Audacity. Now Audacity's HUGE place in the Scheme of Things is it records what it hears. Whatever you can hear, it can hear. So if you can hear your guitar with no pops/crackles, you can click RECORD on Audacity and just play - and Audacity will record it with no pops or crackles (Again, that's the theory, any probs. just ask and I'll see if I can reproduce the conditions and spot an answer!) Now one thing I've never managed to do with Audacity is make it wait to hear a sound, THEN start recording. NCH Wavepad can wait for a sound, that puts it one up on Audacity, but you have to buy it. It's very cheap, so it might be worth buying it for that reason alone - Audacity CAN gove you gaps to edit out if you don't start playing straight away, or if you pause to think of the next chord.
Anyway, the key thing with either of those, or with any other piece of similar software, it's just that in my opinion those two are the best of the bunch, that's not to say there aren't others as good I haven't heard of(!) is that they Record What You Hear. They're not having to make their way through any complicated programs, so there's theoretcially no latency issues, so you should get a clean recording with them. If, by the way, you've got a soundcard from a snotty-nosed company (hallo, M-Audio and the like) who say 'Our soundcards aren't designed to let you record what you hear', it's bull. They've been telling me for years mine won't let you do that - and I've got YARDS of MP3s to prove 'em wrong.
So. You've got your clean guitar take. Now I'd always do that FIRST - here's why. If you've already done the backing track, lining up the guitar so it starts in the right place/places is an absolute, jump-off-a-cliff-type nightmare. You're a couple of seconds out everywhere, guaranteed. You quantize the heck out of it and you're STILL out. I've been there.
Now there might be a better solution than the one in the next paragraph, if there is and someone puts it, or you know a better one, just say and I'll learn - I'm a relative newbie too! But here goes.
Record the guitar onto the computer. Dump the MP3 of the guitar track onto a physical MP3 player - Ipod or MP3 stick or mobile phone or similar - and play the next instrument as you're listening to it. This is where NCH Wavepad REALLY comes into its own, as opposed to Audacity. Audacity will leave a 'tail' of silence at the beginning, NCH Wavepad waits for the first sound before it starts recording. Then you'll have 2 instruments perfectly in time with eachother.
Now bung both wavefiles into Audacity/Wavepad and bounce 'em down as a rough MP3, keeping them saved as separate wave files as well. Now you can listen to the first 2 instruments on your MP3 player and play and record the 3rd in time to what you're hearing. Remember, you can't play the first 2 tracks on the computer because Wavepad/Audacity record EVERYTHING they hear so, because nothing's mixed yet, you'd get a guitar sounding like it's down one end of the street while the other instruments are right on top of you.
Once you've repeated the above steps for ALL the instruments, you can import them into whatever mixing package you use - Reaper's a freebie, but I must admit I'm having SEVERE probs., understanding how it thinks, if you can use it you could help me, or Audacity itself does perfectly good mixing AND you can add plug-ins. And just mix the track.
Now I know the above method works. I'm not saying its the best solution. It's just because it's the one that uses the least possible amount of software, if the cracks'n'pops are due to latency, it should give them the best chance NOT to happen.
Just a last sentence - mono-stereo doesn't matter when you're recording something. When you're mixing, if you have a mono track, you can copy it, pan one hard left, one hard right - hey presto, instant stereo (O.K., it's not stereo just before all the anoraks jump on me, but if it quacks like a duck...)
Say if you have any more problems and I'll try to help, I'm just a newbie too, but I've solved all the problems I've found so far - and there's been a LONG list of them. (Try several years' worth...)
Yours respectfully
ulrichburke