In a HiFi audio system, the power supply is far more than a voltage source.
From an engineering perspective, power delivery forms the foundation for noise performance, reference stability, and timing accuracy, directly affecting analog stages, digital logic, and clock systems.
🔌 1. What Power Supply Noise Really Is
A real-world power supply output is not ideal DC, but a combination of:
- ⚡ DC voltage level
- 🌊 Low-frequency ripple (50 / 60 Hz)
- 📡 High-frequency noise (switching noise / EMI)
- ⏱ Load-induced transient current disturbances
In HiFi systems, the impact is determined not by total noise alone, but by:
- Noise spectrum distribution
- Coupling paths into the circuit
- Whether noise enters critical references (ground, clock, voltage reference)
🔄 2. Core Engineering Issues of Switching Power Supplies (SMPS)
Typical SMPS characteristics include:
- High-frequency PWM operation (tens of kHz to MHz)
- Very fast current edges (high di/dt)
- Wideband, dense harmonic noise content
These lead to several engineering-level concerns 👇
1️⃣ High-Frequency Noise Is Difficult to Fully Isolate
Even when an SMPS meets electrical compliance standards:
- High-frequency noise can still couple through
- PCB power planes
- Ground return paths
- Cables and connectors
- These frequencies fall precisely within the most sensitive regions of DACs, clocks, and voltage references
👉 Many issues are not about specification limits, but unpredictability.
2️⃣ Ground Reference Modulation 🌐
In mixed-signal and high-speed digital systems:
- Ground is not an ideal zero-potential node
- currents create voltage drops across ground planes
- This results in:
- Digital threshold variation
- Unstable analog reference points
- Increased common-mode noise
In audio systems, ground itself is part of the signal path.
3️⃣ Power Noise → Phase Noise → Jitter ⏰
This is one of the most critical—but often overlooked—mechanisms:
- Clock oscillators are highly sensitive to supply noise
- Power noise is converted into phase noise within the oscillator loop
- Phase noise appears as jitter in the time domain
👉 For DACs, jitter is not a bit error, but a loss of sampling-time accuracy.
🔋 3. Engineering Advantages of Linear Power Supplies (LPS)
The benefits of linear power supplies are rooted in their operating principles:
✔️ 1️⃣ No High-Frequency Switching Noise Source
- Operate at 50 / 60 Hz
- Do not generate PWM harmonics
- Noise spectrum is narrower, more predictable, and easier to manage
✔️ 2️⃣ Cleaner Power and Ground References
- 🧭 Lower wideband noise floor
- 🔗 More stable ground return paths
- 🎯 More favorable conditions for voltage references and clock oscillators
Even when downstream PSRR is limited, circuits operate closer to their optimal conditions.
✔️ 3️⃣ More Linear Transient Current Behavior
- 🧱 Large reservoir capacitors
- 📈 Lower and smoother output impedance
- ⚖️ Improved operating-point stability
This is particularly important for analog output stages and clock modules.
💻 4. Why Digital Audio Devices Also Benefit
From an engineering standpoint:
- ❌ Digital does not mean noise-immune
- ❌ Digital audio is not ideal logic
Key reasons include:
- Logic thresholds are defined by analog voltages
- Clock systems are fundamentally analog oscillators
- Power noise directly degrades timing margins
As a result, the following devices are highly sensitive to power quality:
- 🎵 DACs
- ⏱ Master clocks
- 🔌 USB / SPDIF interfaces
- 🌐 Audio-oriented network devices
🎧 5. Engineering Explanation of Audible Differences
Commonly reported improvements include:
- Lower perceived noise floor 🌑
- Improved focus and coherence 🎯
- More stable imaging and localization 🧩
From an engineering perspective, these correlate with:
- Reduced system noise coupling
- Improved jitter spectrum (especially close-in phase noise)
- Increased stability of power and timing references
🛠 6. LHY Audio's Technical Position
LHY Audio linear power supply designs based on the following engineering considerations:
- In HiFi systems, noise spectrum matters more than efficiency
- Stable, low-noise power improves overall system consistency
- Power supplies should minimize their “participation” in sonic outcomes
Linear power supplies are treated as infrastructure, not tone-shaping tools.
📌 7. Additional Note
LHY Audio offers multiple linear power supply models to support audio devices with different voltage and power requirements.
Selection should be based on the device’s official electrical specifications and actual load conditions.
👉 How to Choose the Right Linear Power Supply for Your Audio Device
✅ Conclusion
From an engineering perspective, the core value of a linear power supply lies in reducing system uncertainty.
Cleaner and more stable power allows audio equipment to operate closer to its original design intent.
