Dear John I was aware of the ability to mix Class I and II construction in a single product, but as I understand it such a product must be treated as if were simply Class I, in that it must have a protective ground connection via its power cord.
I was sure that the AES would not condone removing the safety ground connection where it is needed for safety, and am pleased that you have confirmed that this is the case. All the very best! Keith Armstrong www.cherryclough.com In a message dated 20/03/02 19:19:04 GMT Standard Time, j...@jmwa.demon.co.uk writes: > Subj:Re: Pro-audio and ground lifting > Date:20/03/02 19:19:04 GMT Standard Time > From: j...@jmwa.demon.co.uk (John Woodgate) > Sender: owner-emc-p...@majordomo.ieee.org > Reply-to: <A HREF="mailto:j...@jmwa.demon.co.uk";>j...@jmwa.demon.co.uk</A> > (John Woodgate) > To: emc-p...@majordomo.ieee.org > > I read in !emc-pstc that cherryclo...@aol.com wrote (in <17d.557eff5.29c > a1...@aol.com>) about 'Pro-audio and ground lifting', on Wed, 20 Mar > 2002: > > Class I equipment uses basic insulation plus protective ground bonding > to > > protect against electrical hazards, and must use three-pin mains > connectors > > and three-core mains leads (for single-phase supplies). > > > > The only alternative permitted (in Europe, anyway) for mains-powered > > equipment is Class II - 'double insulation' . This must have no > protective > > ground conductor and must use two-pin mains connectors and two-core > mains > > leads (again, for single phase supplies). > > This is true for consumer products but for professional audio equipment > under IEC/EN60065, an arrangement whereby *parts* of the product meet > Class II requirements while other parts meet Class I requirements has > been accepted by Notified Bodies for some years. These can be shown to > be just as safe as conventional products. > > With regard to your main enquiry, professional audio engineers in the > Audio Engineering Society are severely critical of 'ground lift' > solutions. The correct, and safe, solutions, lie in the signal circuits > that sustain the ground loops. The subject is extensively treated in the > June 1995 issue of the Journal of the Audio Engineering Society. > -- > Regards, John Woodgate, OOO - Own Opinions Only. > http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! >
