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Musician questions

Former Community Member
Former Community Member

Hi there, 2 questions using my Seaward Apollo 500:

1- my radio connection between guitar and amplifier has a separate PSU, so is class 3? Should I simply PAT this as class 2?

2- my bass combo amp is a pretty new Ashdown Studio 15 which does not have any class marking (apart from RoHS CE) so has to be class 1? But this device fails earth continuity and I don't believe it is manufactured to earth the exposed metal parts. Can I ignore this test? If so, for what reason?

Thank you.

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    it is normal practice to earth the audio sockets' metal outer parts to prevent danger under fault conditions.  Screened audio leads connect from mains powered appliances like combo amplifiers to things like metal microphone stands or instruments. If the screen is earthed then it should prevent mains appearing on touchable metal parts due to a fault, shocking musicians. 

    I doubt that the earthing of the audio side was done with electrical safety in mind - the conductors would often be too small to reliably survive an earth fault current and Zs too unpredictable to reliably trigger ADS (especially in the pre-RCD days).

    Connecting the audio side to mains PE actually has a disadvantage in that it can 'import' a fault potential from the mains side.

    I believe the earthing was primarily to reduce interference on the sensitive audio circuit - in the screened cables and connectors in effect created a small Faraday cage around the circuit.

        - Andy.

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  • 0

    it is normal practice to earth the audio sockets' metal outer parts to prevent danger under fault conditions.  Screened audio leads connect from mains powered appliances like combo amplifiers to things like metal microphone stands or instruments. If the screen is earthed then it should prevent mains appearing on touchable metal parts due to a fault, shocking musicians. 

    I doubt that the earthing of the audio side was done with electrical safety in mind - the conductors would often be too small to reliably survive an earth fault current and Zs too unpredictable to reliably trigger ADS (especially in the pre-RCD days).

    Connecting the audio side to mains PE actually has a disadvantage in that it can 'import' a fault potential from the mains side.

    I believe the earthing was primarily to reduce interference on the sensitive audio circuit - in the screened cables and connectors in effect created a small Faraday cage around the circuit.

        - Andy.

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