ground hum

[barryb5]

So, after electing to add a sub to my setup, I've found I've now some nasty low 60 cycle-like hum when I select 'phono' on my amp. The hum is only present with the sub connected to my amp i.e. if I unplug the sub, the hum disappears. In fact, even with sub powered off (yet still plugged in) and connected to the amp, the phono channel still has hum present.

I've tried different RCA cables between sub and amp but to no avail. I've also tried using different plugs in different areas of room but to no avail also. On all other inputs, e.g. cd/ optical etc, the sub works fine with no hum present.

My TT is a debut carbon for what it's worth.

Many thanks for any insights...

 

[Al ears]

So, after electing to add a sub to my setup, I've found I've now some nasty low 60 cycle-like hum when I select 'phono' on my amp. The hum is only present with the sub connected to my amp i.e. if I unplug the sub, the hum disappears. In fact, even with sub powered off (yet still plugged in) and connected to the amp, the phono channel still has hum present.

I've tried different RCA cables between sub and amp but to no avail. I've also tried using different plugs in different areas of room but to no avail also. On all other inputs, e.g. cd/ optical etc, the sub works fine with no hum present.

My TT is a debut carbon for what it's worth.

Many thanks for any insights...

I'll bet your TT doesn't have an earth lead on the phono cables.

 

[barryb5]

It does unfortuanetly, and connected as it should be - was only too hopeful of such a fix!

Anybody any knowledge of using such a device as a ground loop isolator? Have noted thay have a certain frequency response and impedence and am unsure of how it might degrade signal - likely for the worse...

 

[gasolin]

It does unfortuanetly, and connected as it should be - was only too hopeful of such a fix!

Anybody any knowledge of using such a device as a ground loop isolator? Have noted thay have a certain frequency response and impedence and am unsure of how it might degrade signal - likely for the worse...

Not for turntables

 

[Al ears]

It does unfortuanetly, and connected as it should be - was only too hopeful of such a fix!

Anybody any knowledge of using such a device as a ground loop isolator? Have noted thay have a certain frequency response and impedence and am unsure of how it might degrade signal - likely for the worse...

Ah!, in that case does removing the link make any difference? It's usually the phono input as this is the most sensitive of the lot.

Failing that I can only suggest a different sub or removing it entirely. Get a decent set of speakers that don't require a sub to give you the bass you need.

 

[hybridauth_Google_112658120703314018098]

I had a real headache of a ground loop issue with some active monitor speakers recently... Really frustrating! Is the sub connected to the same power point as your other equipment? My understanding is that if it's connected to a different earth, that can potentially cause this sort of thing.

I ended up using one of these to get rid of the hum entirely...
Behringer HD 400 Hum Destroyer
I cannot detect difference in quality, but it does reduce the level a little. You could connect an isolator (that or something similar) between the sub and the amp, I would have thought?

 

[TrevC]

Just make sure the sub is connected to the mains via the same socket as everything else. That should fix it.