[Serge Auckland[_2_]]

"Eeyore" wrote in message
...


Serge Auckland wrote:

"Eeyore" wrote
Serge Auckland wrote:

To paraphrase I think, John Linsley Hood, you can always cut down on
safety margins if you have complete control over circumstances.

There is NOTHING unsafe about Class II equipment. In fact it has to be
intrinsicly SAFER than earthed kit.


In your case, anyone making an equipment change at some stage in the
future could set up a hum-loop.

COULD ? Why WOULD they.

You're inventing fictional problems again.


Not so much a case of inventing fictitional problems, just good
engineering
practice. Whenever I implement any solution to a problem, I try and think
of
what could possibly go wrong in the future and try to plan for it.

All very well but if you introduce a hum loop you can add transformers
THEN !
They're simply not NEEDED here !


If you're sure there won't be any future changes, and you're only trying
to
avoid hum
loops, then your solution is probably fine.

It will be.


That, by the way, is what I
meant in paraphrasing J L-H. I wasn't suggesting your solution is unsafe,
just that if you solve a problem in the minimum way possible, you
sacrifice
the flexibility of a better solution.

Interesting that your AV equipment is all ungrounded. Mine isn't. Some
items
are ungrounded - DTTV box, DVD player, DVD recorder, but the main TV is
grounded, my CD player, pre-amp, and active 'speakers are all grounded.
Turntables are all grounded. It's a mixture, so your solution isn't
generally applicable.

A turntable does not need to be physically GROUNDED. Just connect its
chassis to
the chassis of the amplifier with the cartridge preamp.

I haven't seen a TV with a ground conductor since just about forever btw.

Graham



In my case, two of my turntables (EMT 948 and AEG TRS9000) have built-in
electronics (both audio and control) and require a ground at least for
safety. There is a separate ground-lift facility to float the audio ground
from safety ground, and/or to connect the audio ground to Technical Ground,
separate again from safety ground. The outputs are transformer balanced,
fully floating. My other two turntables are conventionally grounded through
the pre-amp, which in my case has a ground.

As to the TV, it is a Sony Plasma, and definitely has a safety ground
connected to the rear metalwork.

Your earlier comment about laptop power supplies is spot-on. I've recently
had a lot of trouble curing a hum from my laptop which was only apparent
when connecting to my unbalanced hi-fi, but was completely absent when using
a balanced connection. (The sound card is a Digigram VXPocket, which has
balanced ins and outs). I finally solved the problem by finding a power
supply that didn't cause the hum, presumably because this one has a
different arrangement of capacitors. It also has only a 2 wire input whereas
the original supply had a three-wire mains input.

S.


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