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Does anyone know about turntables??? I need some help

parttime crackhead

parttime crackhead

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Right troops, long story short yer auld da is trying to wire a turntable to a pre-amp then to a ghetto volume control then to a set of powered speakers. Seems simple enough but it's buzzing like fuck as soon as I turn the volume past 0. The turntable ground wire is connected to an NI S4, as I can't see anywhere else to ground it to. It works fine when running through the S4 but I want to play records without needing the laptop on.

Any ideas?
 
Make sure only one piece of equipment is connected to mains Earth. Try with the preamp on battery power. If anything has a 2-pin mains connector, try reversing it (mains transformers radiate 50 Hz if the outermost end of the winding is live aot neutral). Gently squeeze up the outsides of the audio plugs to ensure they make good contact. Even try leaving the ground wire off and relying on the outer shielding braid of the audio cables.

Oh, and any turntable relying on a belt belongs in a skip. Direct drive every time -- and the more poles on the motor, the better (most are 4-pole). Idlers are permissible in vintage kit.
 
Si Ingwe said:
Not a fucking clue, your wiring is beyond complicated & that comes from someone living within a vast electrical spaghetti junction. But it does sound like grounding...
Click to expand...

It's not that complicated, it's just wired to the speakers via a pre-amp & a volume knob.

BecomingJulie said:
Make sure only one piece of equipment is connected to mains Earth. Try with the preamp on battery power. If anything has a 2-pin mains connector, try reversing it (mains transformers radiate 50 Hz if the outermost end of the winding is live aot neutral). Gently squeeze up the outsides of the audio plugs to ensure they make good contact. Even try leaving the ground wire off and relying on the outer shielding braid of the audio cables.

Oh, and any turntable relying on a belt belongs in a skip. Direct drive every time -- and the more poles on the motor, the better (most are 4-pole). Idlers are permissible in vintage kit.
Click to expand...

Thanks, I'll try unplugging the pre-amp. What exactly do you mean by make sure only one piece of equipment is connected to mains earth? I don't think I understand, because the way I see it the speakers, the turntable & the S4 are all connected to mains earth through the plug sockets and I can't really change that.

The turntable ground wire is connected to a ground screw on the back of my S4, I think that may be the problem (although it works fine when playing it through the S4 into Traktor on my laptop) but I can't see where else I can ground it. The desk it sits on is completely wooden.

It's a 1210 btw, it doesn't belong in a skip :)
 
parttime crackhead said:
It's not that complicated, it's just wired to the speakers via a pre-amp & a volume knob.

It's a 1210 btw, it doesn't belong in a skip :)
Click to expand...

Just taking the piss!

If the turntable grounds okay when not grounded to the pre-amp ie to a mixer, then it could well be the ground input that's iffy. Does the horrible sound be familiar to you? I suspect if I heard an ungrounded deck again, I'd recognise that awful sound!

edit- Belt drive, Julie? *shudder* God forbid!
 
If there are multiple connections between mains earth and signal earth, you can form loops. Current flowing around such a loop causes a voltage drop across the resistance (which won't be 0 Ω in practice). This voltage is superimposed on the signal voltage. As a magnetic cartridge is only putting out about millivolts in the first place, you really don't want this.

If there is only one connection between mains earth and signal earth, then there are no loops around which a current can flow.

As long as all the signal earths are joined up, then you will still be protected in the event of a fault. But you should be using an RCD (Residual Current Detector; modern name for what us old-timers used to call an Earth Leakage Circuit Breaker, or ELCB) anyway.

And the Technics SL1210 is direct drive -- though there is no shortage of cheap belt-drive look-alikes. (My own cheap 1210 look-alike even has a belt rim and hook underneath the platter, which must be a common part with a cheaper sister model.)
 
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I need to get my decks out of hiding. I've got a pair of Numark 1625s and dm950 mixer, very basic set up but the decks are direct drive at least. Need to replace the cartridge on one as I managed to snap it off when i was pissed. Think that's why they've been packed away in the cupboard for a couple of years as i never got round to replacing it. Got a pretty big selection of vinyl, mostly old house, garage, hard house and trance, courtesy of my old man running his own dance record shop in the 90s. Id love some 1210s, I was told they stopped making them now though?
 
Is their no earth on the pre-amp? I'd start their TBH. Without a good earth the audio signal has no zero reference and so floats, now the audio signal is sat on top of a whole layer of 'stuff' hence the buzzin...sort of.

Its likely metal cases will be earthed, and it should be safe to link all the earths together, when you say Ghetto volume control what do you mean ?
 
The taking pictures plan got Afromanned last night. I'll do it when I get home tonight.

Allein said:
Is their no earth on the pre-amp? I'd start their TBH. Without a good earth the audio signal has no zero reference and so floats, now the audio signal is sat on top of a whole layer of 'stuff' hence the buzzin...sort of.

Its likely metal cases will be earthed, and it should be safe to link all the earths together, when you say Ghetto volume control what do you mean ?
Click to expand...

There doesn't appear to be a ground connection on the pre-amp. It's the cheapest shittiest little pre-amp I could find tbh.

Ghetto volume control is this -

lc1_02.jpg
 
so thats the pre-amp and you have the output plugged into ?

Nice cable length BTW ;)

I'm assuming the preamp has a plastic shell.

You could try touching the earth wire on the outer of the phone connector on the preamp connection, if that works strip the wire back and form loop to go round the connector.

It could be related to the mains cables so you could try connecting them to alternative sockets but the preamp ground is the most likely cause IMO.
 
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Allein said:
so thats the pre-amp and you have the output plugged into ?

Nice cable length BTW ;)

I'm assuming the preamp has a plastic shell.

You could try touching the earth wire on the outer of the phone connector on the preamp connection, if that works strip the wire back and form loop to go round the connector.

It could be related to the mains cables so you could try connecting them to alternative sockets but the preamp ground is the most likely cause IMO.
Click to expand...

I'll try that, thanks.

That's not the pre-amp. That's simply a volume control, it's meant for a car subwoofer I think. The pre-amp and then the turntable are connected to one side of that. A set of powered speakers are connected to the other side.
 
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