Hi All,
Long time reader, first time poster...
I seem to be encoutering a hum induced by a parasitic current flowing from my pre-amp (Onkyo AVR - Class II with no safety ground connection) to my power-amp (Ghent 125ASX2 module in a box - chassis is safety grounded). When I use a standard RCA interconnect, I always get what sounds like a ground hum. With no input to the power-amp, the speakers are perfectly silent.
So facing this, I was wondering about a couple "home-made" solutions without having to purchase what I perceive to be very expensive isolation transformers...
Option 1:
Could the problem be solved by tapping the reference wire of the interconnect and wiring it directly to Safety Ground? Would this allow a direct path to earth for the parasitic current? I am assuming that since the power amp already has the chassis earthed to Safety Ground that this would equalize potential on both ends, or am I completely mistaken?
The plan is to leave the Signal wire untouched and only tap the "ground" wire.
Option 2:
Would running a wire from the grounding screw in the back of the pre-amp straight into Safety Earth result in the same equalizing of potential? And does this grounding wire have to be installed under the washer or above it?
I apologize if these questions have already been asked before, but my initial search has not turned up anything. I have read the posted article on Grounding and interconnects, but with my limited knowledge means I am not sure how it would apply in my situation.
Many thanks.
Long time reader, first time poster...
I seem to be encoutering a hum induced by a parasitic current flowing from my pre-amp (Onkyo AVR - Class II with no safety ground connection) to my power-amp (Ghent 125ASX2 module in a box - chassis is safety grounded). When I use a standard RCA interconnect, I always get what sounds like a ground hum. With no input to the power-amp, the speakers are perfectly silent.
So facing this, I was wondering about a couple "home-made" solutions without having to purchase what I perceive to be very expensive isolation transformers...
Option 1:
Could the problem be solved by tapping the reference wire of the interconnect and wiring it directly to Safety Ground? Would this allow a direct path to earth for the parasitic current? I am assuming that since the power amp already has the chassis earthed to Safety Ground that this would equalize potential on both ends, or am I completely mistaken?
The plan is to leave the Signal wire untouched and only tap the "ground" wire.
Option 2:
Would running a wire from the grounding screw in the back of the pre-amp straight into Safety Earth result in the same equalizing of potential? And does this grounding wire have to be installed under the washer or above it?
I apologize if these questions have already been asked before, but my initial search has not turned up anything. I have read the posted article on Grounding and interconnects, but with my limited knowledge means I am not sure how it would apply in my situation.
Many thanks.
Does your equipment hum when you connect one channel with only ONE interconnect?
i.e. does the hum start when you connect the second interconnect?
i.e. does the hum start when you connect the second interconnect?
Well, at this point, I have 3 pre-outs in use from the receiver. Stereo front pair to an earthed stereo pre-amp (HT bypass) and a power amp for Centre channel.
With only the stereo interconnects attached, there is a small hum which I have been mitigating with a -10dB attenuator. This seems to work quite well - the hum is barely noticeable beyond a foot or so away.
The centre channel is a new development that I have only just tried to add on. This time, the hum is very much louder than previously. It is very clearly audible at my listening position about 10 feet away.
I am quite baffled by this since the pre-amp and all power amps in use are all connected to the same power strip which should all be at or about the same potential shouldn't it?
With only the stereo interconnects attached, there is a small hum which I have been mitigating with a -10dB attenuator. This seems to work quite well - the hum is barely noticeable beyond a foot or so away.
The centre channel is a new development that I have only just tried to add on. This time, the hum is very much louder than previously. It is very clearly audible at my listening position about 10 feet away.
I am quite baffled by this since the pre-amp and all power amps in use are all connected to the same power strip which should all be at or about the same potential shouldn't it?
you almost certainly have a loop in your grounding and screens.
Back to my question in post 2.
Measure the hum at the power amp output when you have one interconnect attached and then with two interconnects attached.
Adding a centre channel transformer that is isolated from the stereo amplifier should not change the hum on the stereo amplifier.
Check that by measuring the hum when you connect the third interconnect.
Back to my question in post 2.
Measure the hum at the power amp output when you have one interconnect attached and then with two interconnects attached.
Adding a centre channel transformer that is isolated from the stereo amplifier should not change the hum on the stereo amplifier.
Check that by measuring the hum when you connect the third interconnect.
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