A representative OEM engineering case showing how transformer design, shielding, mounting and system integration can help reduce mechanical vibration and low-frequency hum in audio amplifier equipment.
Item |
Project Details |
Application |
Professional audio amplifier and Hi-Fi equipment |
Transformer Type |
Custom toroidal power transformer |
Main Problem |
Audible chassis vibration and 50/60 Hz hum at low volume |
Engineering Focus |
Flux density, winding construction, shielding, mounting and lead routing |
Customer Requirement |
Quieter operation without changing the existing amplifier enclosure |
Project Result |
Reduced audible hum, improved idle noise performance and stable power output |
The amplifier operated normally at medium and high output levels, but the noise became noticeable when the amplifier was idle or playing music at a low volume.
The project involved two different noise symptoms:
Although both symptoms were related to the power supply section, they required different engineering solutions. Mechanical hum is normally associated with transformer flux density, mains quality, core vibration and mounting. Hum from the loudspeakers may also be influenced by magnetic coupling, capacitive noise, grounding, rectifier current loops and internal wiring layout.
The customer required a transformer solution that could fit the existing chassis while maintaining the required output voltage, rated power and temperature performance.
ECKO reviewed the transformer specification together with the amplifier power supply and mechanical layout.
The engineering review covered:
The review indicated that the noise was not caused by one single factor. Transformer operating flux, vibration transfer, magnetic coupling and high-current wiring all needed to be considered together.
The primary winding and core design were recalculated for the complete input-voltage range.
By optimizing the number of primary turns, core size and copper cross-section, the transformer operated further away from core saturation, especially when the mains voltage was above its nominal value.
This helped reduce the transformer’s sensitivity to mains-voltage variation and lowered the risk of audible core vibration.
The primary and secondary windings were arranged to achieve consistent magnetic balance and stable voltage regulation.
Controlled winding tension, even copper distribution and repeatable insulation layers helped reduce internal movement and improved production consistency.
The high-current secondary leads were also arranged to minimize loop area and unnecessary magnetic coupling inside the amplifier.
An electrostatic shield was added between the primary and secondary windings to help reduce capacitive transfer of mains-borne interference.
For noise-sensitive amplifier layouts, optional magnetic shielding can also be added around the toroidal transformer to further reduce stray magnetic field coupling into preamplifier, input and signal-processing circuits.
The shielding configuration and connection method must be coordinated with the amplifier’s grounding and protective-earth design.
The original rigid mounting structure transferred part of the transformer vibration directly to the metal chassis, which made the hum more noticeable.
ECKO recommended:
This mounting arrangement helped reduce vibration transfer without changing the amplifier chassis.
Even a low-leakage toroidal transformer can introduce noise if it is installed too close to sensitive audio circuits.
The transformer orientation was reviewed during prototype testing. Primary leads, high-current secondary leads and rectifier wiring were kept away from low-level input and preamplifier circuits.
Where possible, paired AC leads were twisted and kept short to reduce radiated magnetic fields.
Toroidal transformers can produce relatively high inrush current during switch-on.
Depending on the amplifier power and filter capacitor capacity, ECKO can coordinate the transformer design with:
This helps protect switches, relays and fuses while maintaining reliable amplifier start-up.
The customized prototype was evaluated under both no-load and rated-load conditions.
The verification process included:
The customer also evaluated transformer orientation, lead routing and mounting inside the actual amplifier enclosure.
After the transformer and mounting design were optimized, the amplifier showed a clear reduction in audible transformer hum and chassis vibration.
Magnetic and capacitive interference around the sensitive audio circuits was also reduced, resulting in a cleaner background when the amplifier was idle or operating at low volume.
The final design maintained the required secondary voltages, power output, insulation performance and acceptable operating temperature.
Approved drawings, winding specifications, material requirements and test limits were documented to support repeatable OEM production.
Toroidal transformers are widely used in professional audio and Hi-Fi equipment because they provide:
However, a toroidal transformer is not automatically silent. Correct flux density, winding design, mounting, shielding, grounding and amplifier layout are all important for achieving low-noise performance.
To develop a customized toroidal transformer for your amplifier, please provide:
If possible, please clarify whether the noise comes directly from the transformer, the amplifier chassis or the loudspeakers. This helps our engineers identify the most appropriate solution.
ECKO provides custom toroidal transformers for professional audio amplifiers, Hi-Fi systems, preamplifiers, studio equipment and other noise-sensitive electronic products.
Our engineering support covers specification review, transformer design, prototype production, testing, drawing approval and recurring OEM supply.
Send us your amplifier power requirements, input and output voltages, available dimensions and noise concerns. Our engineering team will review the application and recommend a suitable transformer solution.
Need to reduce transformer hum or power-supply noise in your amplifier?
Send your transformer drawing, electrical specifications or existing sample to ECKO for a customized engineering review.
ECKO ELECTROTECH CO.,LTD provides high-quality custom transformers and wound components for industrial, medical, and renewable energy applications. 20+ years of expertise, ISO9001, CE, cUL/UL certified. Global delivery with 24-month warranty. Contact us today.
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