Custom Low Noise AC/DC Power Supply for Professional Audio Equipment

XGW Digital Technology is a China-based custom AC/DC power supply manufacturer specializing in industrial and application-specific power solutions. This case covers a low-noise multi-output SMPS built for a 500-series analog audio chassis, where power rail cleanliness is part of the signal path.

Customer Background

A professional audio equipment manufacturer came to XGW for a custom power supply inside a 500-series analog audio chassis. The unit mixes sensitive microphone preamplifier circuits with precision analog stages, so the power section is not a back-of-board afterthought — it sits directly in the signal chain. Any residual switching noise rides on top of the audio and shows up at the output.

Design Challenge

The brief left little room for compromise. The main challenges included:

• Multiple positive and negative voltage outputs — the chassis needed symmetric rails alongside the main supply.
• Ultra-low ripple requirement — microphone preamplifier front ends pick up even small rail deviations, so output noise had to stay well below the audible floor.
• Low EMI interference — the supply could not pollute adjacent analog stages or fail radiated-emission limits.
• Continuous operation of all power rails — every rail had to hold regulation under load swings, not just at nominal.
• Universal AC input compatibility — one SKU had to run on mains anywhere the product ships.

XGW Solution

XGW proposed a customized AC/DC power supply architecture matched to the chassis, not a modified catalog brick:

• Universal 90-264VAC input — single global input range, no regional variant.
• Multi-output DC rails — the design carried the required positive and negative rails on one regulated platform.
• Optimized switching frequency above the audible range — pushing the fundamental out of the audio band kept the switching tone away from where the ear (and measurement) is most sensitive.
• EMI filtering design — input and output filtering plus layout discipline brought conducted and radiated noise down.
• Low ripple output filtering — post-regulation and LC filtering on the sensitive rails trimmed residual ripple.
• Customized PCB and transformer design — shielding and winding geometry were tuned for the analog environment rather than cost-per-watt alone.

Application

The resulting supply serves audio hardware where rail cleanliness is audible. Typical uses:

• Professional audio equipment
• Studio recording systems
• Microphone preamplifiers
• Broadcast audio equipment
• Analog signal processing equipment

FAQ

Power Supply · Custom AC/DCAudio · Low NoiseMulti-Output SMPS