Could it be dirty power interference, or fluorescent lighting? Have you tested this in multiple locations? Unshielded guitar pickups? Have you tried swapping out your guitar cable and guitar? Do you get the noise with any set of headphones? One test I might try is recording a loop and playing that back through the headphones. You could pipe in pre-recorded content as well. Does that crackle? Might help you narrow down the source of the issue.
Does this happen on Factory presets? Could be something in your signal chain.
Also, do you have your QC plugged into something else that has a grounded plug, such as a powered monitor? We know the QC’s power supply is ungrounded and could potentially allow noise or hum into the signal.
Depends on your use case. If you need to dial in tones and want a good representation of what’s getting piped out to FOH, you’ll want the best reference monitor headphones your budget can afford. I picked up the Shure SRH1440’s a while back (open back, lots of headroom, pretty accurate freq response) and they’re great for dialing stuff in.
If you’re just rehearsing or jamming, can’t go wrong with some cheap IEMs. I think Shure also makes IEMs that are around $100 US. Armature drivers have enough resistance to handle the signal without overdriving. Freq response isn’t always super accurate with IEMs because they’re designed for a different purpose, so your mileage may vary, but these are my two solutions.
80 ohm Beyerdynamic DT770 here. Great for anything. Be cautious of the 220 ohm options… they may have a bit more detail, but you need a decent amount of power to push them correctly. I have both 220 and 80 of the DT770, and the 80 has turned out to be the one I grab anymore.
No clipping unless I cause clipping in the signal chain somewhere. They’re powerful and clear. Bottom end is punchy and they go reasonably deep. Comfortable. They’re popular for at least some level of studio use, so they’re focus is geared more towards even. I tried them because a sound engineer buddy told me I should, and I’m happy with the price/value/sound.