220V Amplifier Soft-Start Delay Board

Add a controlled power-on stage to a professionally designed amplifier supply. This finished soft-start board uses an NTC-and-relay sequence to limit startup inrush before normal operation, providing a component for a compatible 220 V AC installation.

✅ Limit the initial startup current - Thermistors form the startup load before the relay bypasses them.

✅ Sequence power-on with a delay - The circuit provides an approximately three-second startup interval.

✅ Include temperature-switch inputs - Reserved connections allow suitable external temperature switches in the designed circuit.

Make Startup Behaviour Part of the Power Design

A transformer-based amplifier supply can draw a large current when first energised. A soft-start stage addresses that initial event, separating the power-on sequence from normal running rather than changing the audio signal path.

The board is a mains-voltage installation component for a qualified electrician, not a plug-in consumer accessory. Fit it within a correctly rated, enclosed design; external temperature switches are optional and are not included.

Technical details

• Type: finished AC soft-start board
• Working voltage: 220 V AC
• Listed delay: approximately three seconds
• Listed startup limiting current: approximately 3.5 A
• Size: approximately 85 × 70 × 28 mm
• Temperature switches: separate components

Include a documented soft-start stage in a professionally designed compatible amplifier supply.