Turntable

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

NT

My old vinyl-era Goodmans Receiver has a terminal just for this purpose.

and forgetting the lyrics.

Right, normally, the deck itself will have a separate earth wire. Connect this from the spade on the turntable to normally a terminal on the amp and all will be good.

I use an old SL5 turntable with an Ortofon cart, Its called Concorde, but they seem to still do it in their vinyl reclamation range, no doubt suitably higher priced by now... grin. The SL 5 is a parallel tracker and works very well. Its a Technics. Steer away from the cheaper SL3 its belt driven and they disintegrate. Older direct drive turntables are king after all these years I find. If you are going to digitise stuff, then do play the discs wet in a solution of water and washing up liquid and make sure any grit and general muck is off them. I use a knowin record cleaning bath myself for this. I do not know if its still made but its basically a vertical bath with brushes that are in the solution and a centre spindle allowing manual rotation and cleaning. Brian

That does sound bizarre when a half decent usb sound card could probably do the same and offer many more choices of medium storage! Brian

In message , snipped-for-privacy@gmail.com writes

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.

A 3m extension lead because the supplied lead doesn't reach the amp is another cause. (I shortened it to 30cm to fix it.)

In message , Brian Gaff writes

During our phone discussion, we did establish that he has what amounts to a usb soundcard, but I backed off when he started asking about getting accurate automatic track markers. His intermediate DAT method does this, but my experience of trying to set this up to be automatic and accurate in a PC editor has not been reassuring.

The vast majority of separate decks work/worked as I described. Yes there w ere variants, eg chassis inernally connected to one of the audio screens wa s 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 in sulated 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 i ts 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 pr oducts were too often a victory of marketing over fact.

NT

My TD150 has a two core mains lead. It gives you the choice of grounding the chassis and pickup via a separate earth lead to the pre-amp ground terminal, or either (or none at all) But I've got an SME arm on it. Think I grounded both the chassis and it, before I fitted a disk pre-amp to it. But all you need to do is try them all for the least hum.

ITYM Systemdek with a Rega arm? They usually used a Rega RB250 arm (green blob on a black counterweight). IIRC the arm was earthed to the chassis via the body - there is no trailing wire - and that in turn can be connected to an earth screw at the back of the turntable.

I'd just work through by deduction starting with only the turntable connected to the amplifier - connect a wire from the turntable earth to the amp chassis's earth screw, a known earth if the amp isn't earthed, and no connection.

In message , RJH writes

Thanks, Rob. I have talked to him again and agreed that he will put it all on hold until I can get out to visit and do some proper fault finding. AIUI, the amp has been put away for quite a time and the Systemdek for over a year, so it all needs to be looked at first from a safety perspective before looking for the hum. The hum appears when he plugs the phonos from the turntable into the amp - nothing else connected, so, from your description, there may be an actual fault.

It was used in a different room with a different amp when it was previously working.

It will certainly hum if there is no ground connection to the chassis. It's usual to have the cart grounds going direct to the amp, and not connected to anything else.

The usual cause of hum on a classic record deck is a ground loop somewhere or a completely missing signal earth. Connecting all of the earths together is a fairly common mistake. The one to keep the chassis becoming live should be separate to the sensitive signal earth shield.

I tried mine recently and confess that I had forgotten just how tetchy they were about earthing, stray magnetic fields and acoustic feedback.

Yes. But there are usually only a few options with a decent turntable. And you won't break things by experimenting - just keep the volume set low when doing so.

Well remember a 'separates' system a pal bought new many years ago - IIRC Pioneer. Every part had a three core mains lead. Phono leads supplied too. No matter what you connected to the amp, it hummed due to a ground loop. I'd guess it was designed for two core earth leads, and converted for UK etc sales.

There is also the possibility if the pickup is magnetic that it's picking up hum from the field from a nearby transformer or motor.