Project Background
The customer is a professional recording microphone brand. Its new large-diaphragm condenser microphone requires lower noise floor and smoother high-frequency response in the transformer-coupled output stage. The original transformer showed significant roll-off above 10kHz.
Technical Challenges
- Frequency response deviation from 20Hz to 20kHz must be within ±0.5dB;
- The transformer's own noise must be lower than the microphone's self-noise and not become a bottleneck;
- Size is limited; it must fit into a microphone body with a diameter of 46mm;
- Small batches and multiple models require flexible production.
Our Solution
We adopted a 1:1 Permalloy toroidal core with layered interleaved winding and an electrostatic shield:
- Primary/secondary layered interleaved winding reduces leakage inductance by approximately 40%, shifting the high-frequency roll-off point above 40kHz;
- A copper foil electrostatic shield is added and separately led out to suppress common-mode interference;
- The core is annealed and aged to reduce magnetostrictive noise;
- Epoxy potting is used for fixing, providing moisture resistance and vibration damping.
Delivery Results
- Measured frequency response deviation from 20Hz to 20kHz is ±0.4dB, with significantly improved high-frequency extension;
- Equivalent input noise is reduced by approximately 12dB, achieving the customer's target for recording noise floor;
- The first batch of 2000 samples passed acceptance at once, entering stable mass production;
- Subsequently, we provided similar custom models for two other microphones of this brand.