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Advice Needed: Can't kill the buzz, but the buzz is killing me.

wwenze

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I agree with McFly’s assessment. MUST ground AVR chassis! The importance of solid ground connections for audio components is extremely vital.

1) This is up to the designer as well as the government examiner to decide
2) Grounding a Class II appliance when it should not be grounded can transform it from a safe chassis to a dangerous chassis: In the event there is a fault on the secondary side and the chassis is connect to the secondary, earthing the chassis will connect the secondary side to earth and hence negating the safety benefit of an isolation transformer and allows a closed loop to form on the secondary side without tripping the ELCB/RCD
 

Pecrobet

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1) This is up to the designer as well as the government examiner to decide
2) Grounding a Class II appliance when it should not be grounded can transform it from a safe chassis to a dangerous chassis: In the event there is a fault on the secondary side and the chassis is connect to the secondary, earthing the chassis will connect the secondary side to earth and hence negating the safety benefit of an isolation transformer and allows a closed loop to form on the secondary side without tripping the ELCB/RCD
 

Speedskater

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a]Modifying the plastic case of a Class II (square within a square safety symbol) appliance (or hi-fi component) to run a 'ground' wire to an internal chassis is very dangerous.
b] But a Class II appliance with an exposed metal chassis can be 'grounded'.
c] Never 'ground' to a stake in the garden.
d] Always 'ground' to the Safety Ground/Protective Earth circuit powering the audio equipment.
e] The 'ground' path is to the Neutral in the main breaker box.
f] The 'ground' path has almost nothing to do with Planet Earth. (actually other connections to Planet Earth [like cable TV] are often part of the problem.
 

sam_adams

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2) Grounding a Class II appliance when it should not be grounded can transform it from a safe chassis to a dangerous chassis

When a double-insulated audio device—two-wire AC mains connection with no EGC—is connected using audio interconnects to a device with a 'normal' three-wire AC mains with EGC conductor that connects to a grounded outlet, the internal signal ground of the ungrounded device is connected via the shield of the interconnects to the signal ground of the EGC grounded device. At some internal point in the grounded device there will (should) be a single point of connection for that device's signal ground and the chassis or earth ground. Therefore, connecting an 'ungrounded' device to a 'grounded' device establishes a connection to the EGC in the grounded device—and that's where all the fun starts.

I'll let Bill Whitlock spell it out in better detail:

Bill Whitlock - Interconnection of Balanced and Unbalanced Equipment - Jensen AN-003

Bill Whitlock - Hum And Buzz In Unbalanced Interconnect Systems - Jensen AN-004

Bill Whitlock - Hum Buzz and Ground Loops - New Insights Into An Old Problem AES Toronto 2010

Bill Whitlock - An Overview of Audio System Grounding and Interfacing - Indy-AES-2012

Bill Whitlock - Understanding, Finding, And Eliminating Ground Loops - CEDIA Class EST016

Bill Whitlock - The Myth and Mystery of Analog Signal Interfaces - AES Detroit -2021
 

terryforsythe

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I had a similar issue. The culprit turned out to be my XFinity/Comcast cable. A power strip/surge suppressor with TV cable input/output solved the problem. Actually I tried two. One worked to solve the issue and one did not. The one that worked is made by Monster Power.
 

wwenze

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When a double-insulated audio device—two-wire AC mains connection with no EGC—is connected using audio interconnects to a device with a 'normal' three-wire AC mains with EGC conductor that connects to a grounded outlet, the internal signal ground of the ungrounded device is connected via the shield of the interconnects to the signal ground of the EGC grounded device. At some internal point in the grounded device there will (should) be a single point of connection for that device's signal ground and the chassis or earth ground. Therefore, connecting an 'ungrounded' device to a 'grounded' device establishes a connection to the EGC in the grounded device—and that's where all the fun starts.

I'll let Bill Whitlock spell it out in better detail:

Bill Whitlock - Interconnection of Balanced and Unbalanced Equipment - Jensen AN-003

Bill Whitlock - Hum And Buzz In Unbalanced Interconnect Systems - Jensen AN-004

Bill Whitlock - Hum Buzz and Ground Loops - New Insights Into An Old Problem AES Toronto 2010

Bill Whitlock - An Overview of Audio System Grounding and Interfacing - Indy-AES-2012

Bill Whitlock - Understanding, Finding, And Eliminating Ground Loops - CEDIA Class EST016

Bill Whitlock - The Myth and Mystery of Analog Signal Interfaces - AES Detroit -2021

Don't worry, in a correctly-designed appliance be it class I or II, the secondary ground will never be directly connected to earth for the same reason mentioned in previous post. Secondary ground must be decoupled from earth to reap the benefits of an isolation transformer. Connection of secondary ground to earth is done through a low-value class Y capacitor (for coupling RF) and a high value >1M resistor for coupling DC i.e. static. This is also the reason why whether an equipment has an earth pin or not has nothing to do with whether you will get the half-AC-voltage "electricity leak" and noise, despite this myth being repeated often even on the more technical forums.
 
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