Question Earth Connection

derekhansen

Active Member
I have a Project T1 Turntable hooked up to a NAD phono preamp pp1and then to a Cambridge Audio Azur Amp.
My problem is that there is nowhere for the earth cable to connect on either the CA amp or NAD pp and there is a definite hum through the speakers when the Aux input is switched on (there is no phono input on this Amp.

Any (sensible) suggestions or recommendations?
 

Ron Hilditch

Well-known Member
Have a hum problem with my Project Xtension 10, even with the earth lead connected either to my Primaire R15 preamp or directly to my Denon PMA-2500NE. Found the problem was the leads going from the turntable to the preamp. Moved the leads away from all the others behind the rack, the hum disappeared.
 

camcroft

Active Member

derekhansen

Active Member
This is taken from the suppliers website it might help.
Just had a read of that. Very helpful but unfortunately there is no convenient earthing point in my listening room. I will investigate whether Electrical regulations would allow introducing an outside cable into a power socket outlet. I have my doubts. Thanks anyway.
 
You could take a 3 pin mains plug, attach a lead to the earth pin and then to your TT.
 

John7

Well-known Member
Here's my thoughts for consideration.....

Your TT and Pre-amp have captive leads (and as far as I can tell) no provision for earthing. Your amp may be earthed but there are several models and you do not specify which you have. From what I can see on the net, they all seem have a 3-pin euro connector and no double insulated logo, so assume they are earthed via the mains lead.

Before going further, check the location of the turntable and pre-amp. Are there any electrical devices close by, such as Wi-fi routers/modems, PC's, power supplies or any electrical equipment with large transformers inside? Turntables are very susceptible to induced voltages, so worth paying attention to this.

I would start testing from here...

1 Unplug the phono leads connected to the aux input on the Azure Amp - Is any hum present?

2 Turn the Azure amp off (or lower the volume), disconnect the TT from the Pre-amp and connect the output of the pre-amp to the Aux input of the Azure. Make sure the pre is powered up, turn the volume up on the Azure - Is there any hum present?

3 Plug the TT directly into the Azure. Yes, I know it has insufficient power to "drive" the amp but any defect causing hum should still be obvious - Any hum present?

What you do next depends on the outcome of these checks.......
 
Last edited:

derekhansen

Active Member
Here's my thoughts for consideration.....

Your TT and Pre-amp have captive leads (and as far as I can tell) no provision for earthing. Your amp may be earthed but there are several models and you do not specify which you have. From what I can see on the net, they all seem have a 3-pin euro connector and no double insulated logo, so assume they are earthed via the mains lead.

Before going further, check the location of the turntable and pre-amp. Are there any electrical devices close by, such as Wi-fi routers/modems, PC's, power supplies or any electrical equipment with large transformers inside? Turntables are very susceptible to induced voltages, so worth paying attention to this.

I would start testing from here...

1 Unplug the phono leads connected to the aux input on the Azure Amp - Is any hum present?

2 Turn the Azure amp off (or lower the volume), disconnect the TT from the Pre-amp and connect the output of the pre-amp to the Aux input of the Azure. Make sure the pre is powered up, turn the volume up on the Azure - Is there any hum present?

3 Plug the TT directly into the Azure. Yes, I know it has insufficient power to "drive" the amp but any defect causing hum should still be obvious - Any hum present?

What you do next depends on the outcome of these checks.......
Thank you John7. I will run through your check list and post the results.
 

Mark.Yudkin

Distinguished Member

derekhansen

Active Member

Mark.Yudkin

Distinguished Member
I tried the recommended NAD fix (essentially fitting the earth cable spade under one of the rear panel screws on the CA amp) It definitely reduced the hum although it’s still detectable when I turn the volume up high.
Some hum at high volumes is normal, especially with TT inputs, and is not caused by earthing issues. You may well be able to reproduce the same hum after disconnecting the TT from the NAD.

If you can't hear any hum at your normal listening distance and volume, there is no need for concern or action.
 

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