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Re: Ground Loop Hum
Posted: Wed Feb 14, 2018 10:42 pm
by Cyndale
Fran wrote: ↑Wed Feb 14, 2018 10:12 pm
Can you try moving your cables (interconnects) around a bit and see if the intensity of hum changes? Also try disconnecting the components one by one in your system to see if one is contributing hum? I've seen SPDIF connections doing this for example.
I disconnected all interconnects and changed them round, no difference.
I did notice hum increase or decrease if I wiggled either of the power amp cables.
Re: Ground Loop Hum
Posted: Wed Feb 14, 2018 10:44 pm
by Fran
You definitely want the amps safety grounded - connected to mains earth in other words. Especially with valve amps in particular.
Its worth putting in half an hour to reposition the amps, cables etc to see if some re-routing could kill the hum for you. I take it these are commercial valve amps, or are they DIY ones?
Re: Ground Loop Hum
Posted: Wed Feb 14, 2018 10:57 pm
by Ivor
Fran wrote: ↑Wed Feb 14, 2018 10:44 pm
Its worth putting in half an hour to reposition the amps, cables etc to see if some re-routing could kill the hum for you.
This clicks with me. I had a horrible hum and it was because my phono stage was too near the valve power amp. Not near in any obvious sense but still
too near. Moved bits about... problem solved.
Re: Ground Loop Hum
Posted: Wed Feb 14, 2018 11:12 pm
by Cyndale
Fran wrote: ↑Wed Feb 14, 2018 10:44 pm
You definitely want the amps safety grounded - connected to mains earth in other words. Especially with valve amps in particular.
Its worth putting in half an hour to reposition the amps, cables etc to see if some re-routing could kill the hum for you. I take it these are commercial valve amps, or are they DIY ones?
Croft valve amps, have had them for centuries, ha!
Re: Ground Loop Hum
Posted: Wed Feb 14, 2018 11:16 pm
by nige2000
aghh.... doesn't everybody love ground
Re: Ground Loop Hum
Posted: Thu Feb 15, 2018 1:42 pm
by Derek
Somewhere to keep your feet.
Re: Ground Loop Hum
Posted: Sat Feb 17, 2018 12:50 am
by Cyndale
Hhhmmm! So that's the best anybody can do!
Re: Ground Loop Hum
Posted: Sat Feb 17, 2018 11:18 am
by nige2000
if you cant resolve it externally,
its probably time to look inside to see what way it was earth grounded and if it can be improved apon
if its crudely connected chassis earth to signal ground an alternative is likely to easily solve it
Re: Ground Loop Hum
Posted: Sat Feb 17, 2018 11:40 am
by Cyndale
Just wondering... I have the amps on a 3-tier Target stand. Power amp on top, preamp in middle, power amp at bottom.
Could the metal stand be having an influence?
Re: Ground Loop Hum
Posted: Sat Feb 17, 2018 2:33 pm
by Fran
Is the preamp active or passive?
Are you confident opening up the bottom of the amp where there are lethal DC voltages - not like AC these are much more dangerous?