The "ground" problem that can not be ignored in the audio entry

The term "ground" usually refers to a zero-voltage point (GND), but not all sockets are connected to true ground. The primary function of the connector housing is to provide shielding and prevent external interference. Another key element is the grounding pin in the power cord, which is designed to protect against electrical shocks by providing a safe path for fault currents. Therefore, the power ground should always be connected to the chassis for safety.

Many audiophiles focus heavily on signal cables and power lines, understanding their impact on sound quality. However, few realize that the ground wire itself can also influence the clarity and noise level of the audio. Signal cables often have a grounding terminal in addition to the signal path. For example, from a CD player to the preamplifier and then to the power amplifier, the signal travels along this path, with the ground playing a critical role in maintaining signal integrity.

Have you ever considered how a ground wire might take a long, winding route—from the CD player to the power outlet, through the preamp’s power line, and then to the power amplifier? Electricity doesn’t always follow a straight path; it takes whatever route is available. This can lead to potential differences and interference, especially if different parts of the system aren’t properly grounded.

The issue arises when the ground potential of the preamplifier or CD player differs from that of the power amplifier. This mismatch can introduce unwanted noise and degrade the overall sound quality. To solve this, one effective approach is to remove the ground connection from the preamplifier and CD player, leaving only the ground wire of the power amplifier. While this seems simple, the challenge lies in implementing it correctly without compromising safety or performance.

Some people attempt to remove the ground pin from their plugs or use non-grounded cables. Others prefer a less destructive method, such as isolating the grounds using resistors or capacitors. This requires careful consideration of the circuit layout, particularly how the ground and chassis are shielded. Proper grounding involves not just physical connections, but also the arrangement of the circuit’s internal ground paths.

It's important to understand that in any circuit, current must return to its source. Whether it's a solid-state or tube-based system, the ground serves as the return path. When voltage passes through components and into the load, it must return via the ground. This return path is typically tied to the filter capacitor’s common point or the regulator’s reference. Therefore, the ground wire should be at least as thick as the power wire to handle the same current levels.

Keep in mind that with dual power supplies, the total current doubles. For instance, in the power amplifier stage, the speaker ground is a critical path for the current flowing through the speakers. It connects back to the filter capacitor and the power transformer, forming a loop. Sometimes, a bridge output configuration may be used instead.

Some enthusiasts focus on the output of tube amplifiers but overlook the importance of the output transformer’s center tap. Simply using a thick ground wire won’t help if the center tap isn’t properly connected to the output stage. Additionally, the cathode resistor of the power amplifier tube should be placed close to the filter capacitor to ensure a clean ground loop.

Now, let’s talk about the chopping current in the ground. Mains power is typically 50Hz or 60Hz AC, and after rectification, it becomes a pulsating DC with a frequency of 100Hz or 120Hz. This ripple creates a loop between the filter capacitor and the voltage regulator, where both high-frequency voltage and current can cause noise. Any ground connection in this area will pick up this noise, making it a major source of interference. Therefore, it's best to keep the ground connection of the filter capacitor as close as possible to its location and avoid mixing it with other ground wires.

How should you arrange the ground wire? In general, consider the current flow. High-current paths should be routed directly back to the main ground point, following a clear path. Try to limit the number of ground paths and avoid connecting them together unless necessary. A “star connection” method is often used, where each circuit’s ground is connected to a single central point, minimizing interference between different sections.

Finally, let’s discuss the concept of “screen grounding.” The main purpose of screen grounding is to connect the chassis to a single, stable point to reduce electromagnetic interference. Some people use thick copper bars or soldered connections, thinking that a poor connection will create noise. In reality, a 100-ohm resistor and a small capacitor (like 0.1µF) are often better choices. The best place to connect the screen is near the input stage of the entire system, as the closer the screen is to the input’s potential, the more effective it will be in reducing noise.

The ideas presented here are just the basics. There are many more advanced techniques and considerations that aren’t easy to explain in detail. Some people ask me how to connect the ground properly. The truth is, there’s no universal solution. It depends on the system, the layout, and the type of equipment being used. Ultimately, the best way is to experiment and find what works best for your setup. Don’t assume that one grounding method fits all—different designs require different approaches.