----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
>
> You should use a transformer for a few reasons (as was
> already covered) like line surges and safety. It is against
> code to EVER ground a neutral to anything connected to
> something external, so the neutral has to float. You could
> float the entire negative rail from chassis, but then the
> issue becomes spikes from the power line into the PA and
> harmonics from the rectifiers into the power mains. You
> certainly could design a system that would use the power
> mains safely and not break codes, but it would require some
> care.
>
> The real problem is knowing the ESR of the transformer.
> Certainly it isn't as low as it could be because of the fact
> it is a control transformer, but a choke input would help a
> lot. You could get a power factor close to unity rather than
> the very poor power factor of a capacitor supply, so you
> might be OK if the choke is a good one.
>
> 73 Tom
>
Sounds like a good application for a switch-mode supply.
Mike W4EF..............................
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