MidiMagic
2K Club - QQ Super Nova
- Joined
- Jul 5, 2010
- Messages
- 2,172
Oh the hums I have encountered as a service tech. Here are some things to think of:
1. Ungrounded turntable chassis.
2. Too many connections to ground to the same component - a ground loop.
3. Too many ground connections between components - a ground loop.
4. Hum field picked up by the magnetic cartridge (a wall wart transformer or that VARIAC). The hum level might change when you move the arm.
5. Phono to preamp leads are too long. Move the preamp next to the phono.
6. Is rumble being mistaken for hum? If the hum quits when you lift the stylus, it's rumble.
7. Is there some item (e.g. an electric clock (motor), fan, or fish tank pump) that is vibrating the table the turntable is on?
8. The hum was intermittent - it happened only when the house furnace blower was running. It vibrated the floor and the table the turntable was on.
9. This setup had balanced line cables between preamp and powered speakers. But a cell phone charger was next to a balancing transformer.
My favorite hum poser was one where the owner and I were trying everything to get rid of hum in the right channel. Then, after 3 hours of testing, I noticed the hum was still there when the amp was turned off. Someone in the next apartment had hung an electric clock (motor driven) on the other side of the wall.
1. Ungrounded turntable chassis.
2. Too many connections to ground to the same component - a ground loop.
3. Too many ground connections between components - a ground loop.
4. Hum field picked up by the magnetic cartridge (a wall wart transformer or that VARIAC). The hum level might change when you move the arm.
5. Phono to preamp leads are too long. Move the preamp next to the phono.
6. Is rumble being mistaken for hum? If the hum quits when you lift the stylus, it's rumble.
7. Is there some item (e.g. an electric clock (motor), fan, or fish tank pump) that is vibrating the table the turntable is on?
8. The hum was intermittent - it happened only when the house furnace blower was running. It vibrated the floor and the table the turntable was on.
9. This setup had balanced line cables between preamp and powered speakers. But a cell phone charger was next to a balancing transformer.
My favorite hum poser was one where the owner and I were trying everything to get rid of hum in the right channel. Then, after 3 hours of testing, I noticed the hum was still there when the amp was turned off. Someone in the next apartment had hung an electric clock (motor driven) on the other side of the wall.
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