I feel a slight tingle when I touch my amplifier's metal body. What's going on?

Stop and take this seriously. That tingle is leakage current reaching the chassis, and it means the protective earth that should be carrying it away is not doing its job. This is a safety issue first and an audio one a distant second.

The usual cause in Indian homes is a socket whose earth pin was never actually connected, or was connected once and has since corroded or been disturbed during renovation. The equipment is doing what equipment does: a small amount of leakage current from the power supply flows to the metal body, and with a working earth it drains harmlessly. Without one, you become the path when you touch it. A tingle today; under different conditions, wet hands or a bare floor, it can be considerably more.

What to do. Get an electrician to verify the earth with a proper tester, an earth loop or socket tester, not a neon screwdriver. The screwdriver tells you a wire is live; it tells you nothing useful about whether the earth is present and low resistance. If the socket fails, the fix is on the house wiring side and it is the electrician's job.

What not to do. Do NOT "solve" it with a two-pin adapter or by snapping off the earth pin. That removes your protection entirely: the tingle may vanish because the chassis is now floating, but so does the only path that would trip a breaker if a real fault developed. The tingle is a warning light. Taping over a warning light is not a repair.

A useful side effect: once earthing is fixed, any background hum in the system usually disappears too. Leaky earth and hum travel together, and I have lost count of the hum complaints that turned out to be an earth pin connected to nothing.

If the earth tests fine and the tingle persists, the equipment's own power supply needs authorised service, as per brand and distributor policy. Do not open it yourself.

Fix this before the next movie, not after. Everything else in this troubleshooting section can wait a week; this cannot.