Turntable Hum, could it be no grounding wire?

[Geoman076]

My nephew has a newer model (Sony) inexpensive turntable. I recently got him a vintage receiver (thanks Clay!) in near mint condition, but when I hooked it up, I got that loud speaker hum that I used to get sometimes with my Bangor Olufson when I didn't have the ground wire hooked up (I think that's what caused it). I think it is funny that my nephews TT doesn't have a grounding wire.

So , the problem is that whenever we try to hook up his TT to a receiver, there is a loud hum from the speakers. His TT has no ground wire like most TTs have. The radio works perfectly. Right now he has to plug his TT into the Aux plugs, which works OK. Do I have to somehow ground his TT?? What could be causing this and what's the solution?? Thanks for your suggestions.

George

[Sckott]

Some turntables are already grounded. My P3 Rega is like that.

But why are you plugging in that TT into AUX? Ya need to use the PHONO pre stage that might be on the receiver???

Unless the TT has a ceramic cart you HAVE to use an RIAA curve pre amp. Most vintage receivers have that.

The infamous "Phono" input.

But you DID say recent table. I wonder if the table already has a pre built in??

[Dave]

Or it could be a MM/MC issue if the pre has both inputs.

[Geoman076]

It only makes the hum when it is plugged into the phono inputs, that's why it's plugged in to the Aux.

[Dave]

Originally posted by Geoman076
It only makes the hum when it is plugged into the phono inputs, that's why it's plugged in to the Aux.
Where's the TT plugged in George? I'm thinking of a ground loop possibility.

[Sckott]

What model is this TT?? Some recent tables that sell for cheap have a pre built in sometimes.

Dave could be correct. Ground loop or a poor cart connection. Mystery gets wider!

[duff138]

Originally posted by Sckott
What model is this TT?? Some recent tables that sell for cheap have a pre built in sometimes.

Dave could be correct. Ground loop or a poor cart connection. Mystery gets wider!


definitely. check to see if the TT has a built in phono amp. It must because otherwise it would not work in the AUX.

[Geoman076]

The turntable is a Sony PSLX250H.

[Sckott]

Yahoo Sez:

Features
Fully-automatic operation
33-1/3 and 45 rpm speeds
Belt drive system
Static balance tonearm
Convenient, front mounted controls
Supplied moving magnet phono cartridge
Bonded diamond stylus
Supplied dust cover
Fully Automatic Operation Turntable
Built- In Phono Pre-Amp

So, the sucker DOES belong in the AUX.

Try taking a very small piece of wire and ground the left negative to the chassis of the receiver. Do it while it's on and idle and see what happens.

[Geoman076]

Thanks for the info Sckott. No wonder why they are starting to make receivers that do not have a phono stage.

[Sckott]

I thought you got that deck for the sake of having a real MM Phono stage:confused: Well, anyway, it's a decent table to start out. Take a good look and make sure it's not JUST the AUX that hums and that the cart, if it has visible wiring, that it's secure.

That little Sony doesn't have a ground wire. For it's own reason (Pre is inside) there IS no reason for a ground. Let us know.

[GabeG]

It sounds like the problem is solved by using the Aux input. You were overloading the receiver's Phono input because of the turntable's built in pre-amp.

However, you might want to disable the turntable's electronics and try letting the reciever do the job since it's likely it will have better electronics.

I'm not familiar with that table (and don't have time to check Sony's website), but I'm positive there is a switch somewhere on the turntalble to bypass its electronics. If its not on the back or underneath, try removing the platter.

[greg_t]

There is a switch under the platter on the 250 that you can use to turn the built in pre-amp on or off. You don't actually have to remove the platter, just turn it until you see the switch. It is at the back of the turntable under the platter.