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Help! Amp humming!

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Niklas S

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Jan 13, 2024
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UPDATE:
I found a way to make it work with a 9 ft extender cable instead of the 15 ft one. And the 9 ft cable I got was thicker and better quality. The hum is about 90% gone now. It’s still present if I turn up the volume too loud, but I can’t distinguish it at all with music playing and it is SO much better. I will stick with that for now.
Thank you all SO MUCH for your help!! I have spent so much time trying to find a solution, and I couldn’t have done it without your help.
Thank you!
God bless!
 

ban25

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UPDATE:
I found a way to make it work with a 9 ft extender cable instead of the 15 ft one. And the 9 ft cable I got was thicker and better quality. The hum is about 90% gone now. It’s still present if I turn up the volume too loud, but I can’t distinguish it at all with music playing and it is SO much better. I will stick with that for now.
Thank you all SO MUCH for your help!! I have spent so much time trying to find a solution, and I couldn’t have done it without your help.
Thank you!
God bless!
Do you have a ground wire connected between the ground lug on the turntable and the one on the pre-amp?
 

GXAlan

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The hum is about 90% gone now. It’s still present if I turn up the volume too loud, but I can’t distinguish it at all with music playing and it is SO much better. I will stick with that for now.

If the better shielding helped, try adding a ferrite choke!
 
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Niklas S

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Do you have a ground wire connected between the ground lug on the turntable and the one on the pre-amp?
The thing is, there isn’t really a spot on the turntable for a ground wire. So the radio guy in town just wired it on the left and right phono it seems. But it doesn’t seem to do any difference for me when I attach it to the amp, so maybe he did it wrong or something.
 

sergeauckland

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The thing is, there isn’t really a spot on the turntable for a ground wire. So the radio guy in town just wired it on the left and right phono it seems. But it doesn’t seem to do any difference for me when I attach it to the amp, so maybe he did it wrong or something.
Not all turntables have a separate ground wire. Those that do, use the ground wire to ground the pickup arm metalwork when that is separate from the turntable's own safety ground. Of course if the turntable is double insulated, then it won't have a safety earth, but the arm metalwork, which is part of the cartridge leads screening does need to be earthed to the amplifier. This can be done through the phono leads. Rega, for example, does this with their RB250/300arms which don't have a separate ground lead. If your 'radio guy' earthed the arm through both Left and Right phonos, he's created a hum loop right there, he should have done it only through one, not both. However, as the two are presumably close together, the loop will be small so not too serious, but does indicate a lack of knowledge.

A 9ft extender is still excessive, will affect the frequency response of the cartridge, and will still pick up more hum than ideal, but if it works for you, OK

S.
 
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Niklas S

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Not all turntables have a separate ground wire. Those that do, use the ground wire to ground the pickup arm metalwork when that is separate from the turntable's own safety ground. Of course if the turntable is double insulated, then it won't have a safety earth, but the arm metalwork, which is part of the cartridge leads screening does need to be earthed to the amplifier. This can be done through the phono leads. Rega, for example, does this with their RB250/300arms which don't have a separate ground lead. If your 'radio guy' earthed the arm through both Left and Right phonos, he's created a hum loop right there, he should have done it only through one, not both. However, as the two are presumably close together, the loop will be small so not too serious, but does indicate a lack of knowledge.

A 9ft extender is still excessive, will affect the frequency response of the cartridge, and will still pick up more hum than ideal, but if it works for you, OK

S.
I think he said he earthed it though the phono cable or something. But then he also made a seperate ground cable. Sounds weird? I’ll try to take a picture of the inside of the turntable where the ground cable is connected.
When the turntable is on and I touch the phono cable plug, the hum lessens a lot. This could indicate a ground problem right?
 
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