Protection Modules

Soft Start Module

The common use of toroidal transformers in audio equipment has solved a great many problems but created others.  One problem is that the use of smaller magnetic cores in toroidal transformers has resulted in what is known as high ‘inrush’ current at power up.

One answer is to upgrade the fuse rating of the equipment.  In doing so, the fuse fitted becomes less likely to blow under fault conditions and by the time it does so, more damage has taken place.

The SSM1 addresses these problems completely automatically:

At power-up, the mains supply is connected to the equipment by a heavy duty relay and via a bank of ballast resistors.  After a specified time, this bank of ballast resistors is removed from circuit by another high current relay – the mains supply is now connected for full operation. All this happens automatically with no intervention from the operator and with no need for any other power supply than the incoming mains itself.

Each aspect of the circuit has been well proven for reliable operation with RF suppression at each critical point to ensure silent operation.  Incorporated on the circuit board are points to which an auxiliary trip such as a thermal overload device may be simply attached to provide extra protection for the equipment.

The SSM1 needs only the addition of a low-current mains switch to complete the installation and the added advantage of needing only the manufacturer’s specified fuse, fitted on the module, completes one of our most popular designs.


Please Note:  The SSM1 is intended to protect the mains supply fuse against surge current excesses and is not for protection of any connected loudspeakers.  For this purpose, a dedicated loudspeaker protection circuit will be required.

SSM2 Soft Start Module - smaller footprint

Based on the time-tested SSM1 unit, this new module is now available in a much reduced size.

Whereas the SSM1 could not be easily accommodated in some applications such as the Naim range of power amplifiers.

This new compact unit may be installed into some models of this range of amplifiers with all the properties associated with less inrush current at power-up, such as less thermal impact on the transformers and circuits of the amplifier and a reduction in blown fuses or mains tripping. This can lead to a longer service life for any amplifiers equipped with this device.

Maximum load at 240V AC is 1KVA – 1000VA.

Installing this unit necessitates working with the high voltage circuits within any equipment and it is crucial that the work is carried out by suitably competent and qualified technicians.

Comes as customary with our CD of circuits and data to gain the best from this product.