On Tuesday, 23 October 2018 11:07:59 UTC+1, Bill wrote:
In message ,
tabbypurr writes

Record deck metalwork needs to be connected to amp case, not earth. Amp
can be earthed or not. Hum means any of: ground wire not connected to
amp case bad connection somewhere on the screened leads or deck not
often, use of a lead that isn't screened

The reason I'm asking is that my last 3 turntables were not like this.
A Connoisseur thing with a long external belt drive had 2 core mains to
the little motor and separately earthed-to-the-amp pickup arm.
The Thorens TD124 had earthed to the mains metalwork, but the pickup was
mounted on the wooden side panel and earthed to the amp.
Similarly a Technics SP15 was just mounted on a wooden plate, with the
pickup separately earthed to the amp.

The Systemtek deck in question apparently cost over £900 when bought new
in the days when pounds were notes and worth something. I would hope it
had some thought put into safety, earthing and so on, hence the
question.

The vast majority of separate decks work/worked as I described. Yes there were variants, eg chassis inernally connected to one of the audio screens was also fairly popular, usually on lower cost decks. That does mean they are not always compliant with current legal safety requirements for workplaces, but safe if the user connects the earth wire to an earthed amp. Double insulated decks - many are, some aren't - are compliant regardless of whether the amp is earthed or the chassis lead connected.

If someone paid £900 it was more for the art aspect of the deck than its sound quality. It didn't cost anything like 900 to get top audio quality.. No doubt the marketing blurb said otherwise.

There was also the high ticket Linn sondek that only did one speed! Hifi products were too often a victory of marketing over fact.


NT