Frequently Asked Question

(Both devices) - Experiencing a hum? Please read these safety standards
Last Updated 2 years ago

Safety regulations:

According to BS EN60065 a "touch current" of up to 1mA is permissible for Class 2 (2-Pin) audio equipment.

This level of current is considered safe by legislators and experts worldwide. EN60065 is a so-called harmonised standard and applies in OZ/NZ, the EU and the USA plus many other countries.

This touch current is a result of the need for a so-called "Y-Capacitor" that links the mains and the DC output in power-supplies to ensure EMC regulation compliance. So some "touch current" will always be present in any audio/av system composed entierly out of 2-Pin mains connection appliances that do not get another earth connection (e.g. Aerial, Satelite/Cable TV) and this can also lead to hum issues in such systems.

At iFi we have optimised our power supplies for the lowest amount of touch current that still allows us to pass EMC regulations. As a result our power supply units and attached devices produce a touch current of around 0.1mA typical, that is 10% of the legal limit and actually in compliance with the standards for medical (including cardio related) equipment in practice.

For the case of unplugging the iCan from the source, you have no audio feed nor any connection to ground/earth. Under these conditions some hum is normal. How much depends on gain and how sensitive the headphones are, therefore you'll need to correctly connect the iCan SE to the rest of the system that will have an earth.


All these issues disappear when the laptop is connected also, as it provides a proper earth connection. If a system is composed only out of 2-Pin mains connection appliances and experiences either hum or subjectively disagreeable touch current (even if legal limits are complied with) or both, adding a supplementary earth connection will solve these issues.

A supplementary earth or the iFi iGroundhog:

A supplementary earth connection is not a safety feature and the system will be safe without. The supplementary earth instead drains the "touch current" to earth and establishes a correct ground for the whole system. In practice a supplementary earth connection may be made by running down to the hardware store or the local B&Q and getting some green/yellow wire as well as a British Standard mains plug. Remove the live and neutral pins entirely (so nothing in this plug can ever make a connection with anything except earth) and attach the green/yellow wire to the remaining earth pin. The other end of the green/yellow wire may then be attached in a suitable manner to the equipment. Often fitting a RCA or 3.5mm plug (green/yellow to ground/sleeve/ring) and using this in an unused input is the easiest way.

If you want to avoid this DIY cable, then use the Groundhog - its already built for you!

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