Amp noise comes from a few specific places, and you fix them in order of impact. Most "my amp is noisy" problems are too much gain, single-coil hum, or a grounding/cable issue — not a broken amp.
Turn gain down first. Every point of gain multiplies hiss. If the noise only appears at high gain, that is the cause — back it off and use a boost pedal for tightness instead of cranking the amp.
Add a noise gate. A noise gate (e.g. ISP Decimator, Boss NS-2) placed after your drive pedals silences the hiss between notes without killing sustain. Essential for high-gain and metal.
Fix single-coil hum. Single-coils hum by design (60-cycle hum). Rotate so your body shields the pickups, move away from screens and dimmers, or use noiseless/humbucker-sized pickups. Humbuckers cancel this hum entirely.
Check grounding & power. A loud hum that changes when you touch the strings is a grounding problem — try a different outlet, avoid daisy-chained power, and make sure the amp and pedals share a clean ground.
Swap the cable. A cheap or failing instrument cable adds buzz and crackle. Use a good shielded cable and keep it away from power supplies.
💡 Order matters: gain down → gate → shielding → power/ground → cable. Fix the biggest cause first and you often never reach the small ones.