Deepdark
Well-known member
maybe you mixed your analog ground with shield ground, or have a little ground loop somewhere
Really strange hum issue! (Please help)
- Thread starter ForthMonkey
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Audio1Man
Well-known member
HUM in Analog circuitry is usually found in two forms.
1. Sine wave, low harmonics. This is typical Magnetic or Electric field pickup.
2. Line related high harmonics. This is typical current related non sine (rectified saw tooth type wave forms) that get into the Analog signal chain.
Type 1 usually can be reduced by bigger spacing or a shield.
Type 2 can be removed by proper layout and correct grounding. The Charging currents must only charge the terminals of the big storage capacitors. The discharge currents must come from the terminals of the big storage capacitors. This current path then does not share any charging currents except the capacitor terminals.
See my attached drawing. Keep lead close to each other or twist them. Make sure that the common ground of the PS only has one place that is connected to the MAIN SIGNAL GROUND.
Good hunting
Duke
1. Sine wave, low harmonics. This is typical Magnetic or Electric field pickup.
2. Line related high harmonics. This is typical current related non sine (rectified saw tooth type wave forms) that get into the Analog signal chain.
Type 1 usually can be reduced by bigger spacing or a shield.
Type 2 can be removed by proper layout and correct grounding. The Charging currents must only charge the terminals of the big storage capacitors. The discharge currents must come from the terminals of the big storage capacitors. This current path then does not share any charging currents except the capacitor terminals.
See my attached drawing. Keep lead close to each other or twist them. Make sure that the common ground of the PS only has one place that is connected to the MAIN SIGNAL GROUND.
Good hunting
Duke
ForthMonkey
Well-known member
Deepdark said:
My audio board's ground and psu board is same.And it's connected to chassis.It's the way of get rid of humming without turn on gear.
Audio1Man said:HUM in Analog circuitry is usually found in two forms.
1. Sine wave, low harmonics. This is typical Magnetic or Electric field pickup.
2. Line related high harmonics. This is typical current related non sine (rectified saw tooth type wave forms) that get into the Analog signal chain.
Type 1 usually can be reduced by bigger spacing or a shield.
Type 2 can be removed by proper layout and correct grounding. The Charging currents must only charge the terminals of the big storage capacitors. The discharge currents must come from the terminals of the big storage capacitors. This current path then does not share any charging currents except the capacitor terminals.
See my attached drawing. Keep lead close to each other or twist them. Make sure that the common ground of the PS only has one place that is connected to the MAIN SIGNAL GROUND.
Good hunting
Duke
My hum is absolutely first one.I tried everything to get rid of but no luck.I put it on away from power trafo but no luck again.Tried bigger caps,no luck again and again.But my regulators have problem i guess.Cause i burnt one of LM317,soldered new one and hum gone away.Really pure sound but signal distorted.Then i desoldered regulator and soldered again,and got normal signal level with hum again.Can't understand...
I will check out your document.Thanks!
