Originally Posted by Blackdevil77
Now there we go! Thanks!
Careful. That is another Forrest Gump type of solution: "life is like a box of chocolate, you never know what you are going to get!"
That optical solution may or may not resolve your problem. Indeed, the Oppo may not the issue but rather the trigger. Yes, I know the hum went away when you unplugged the HDMI cable but does not mean it was the problematic component. Here is the theory.
Consumer audio products by definition are broken. Yes, let me repeat: consumer audio products are fundamentally broken. This is why you get hum randomly and in many instances solutions don't seem to exist. The problem occurs because the ground is used as part of the communication channel. All audio products will cause some amount of leakage into the ground of the product. This is also by design. So you can try all you want with outlets and such but the devices themselves will create voltage differentials by their very nature. Have you ever felt a slight buzzing/shock when you touch the case of an electronic device, especially with the back of your hand? If you so, you are experiencing that leakage from the hot lead to the enclosure of the device. The current is low enough that won't kill you and hence the reason it passes UL certification and such. But it is pretty high with respect to small audio signals. Standard unbalanced audio interconnects unfortunately use that ground as one leg of their signal and hence, will interconnect the two pieces of electronics and different voltages and cause the current to flow and cause the hum.
The HDMI interface among its other ills also has a ground connection. Indeed, the source provides a 5 volt signal to enable plug-and play. So when you connect that HDMI you wind up changing the ground potential of your processor since it is now coupled to the Oppo. That change may actually be then causing a ground loop between the processor and amplifier to be elevated. The optical product will change this situation but not necessarily fix anything. The optical interface has electronics at both ends together with power supplies of their own. That power supply yet again will supply its own ground potential. Maybe you get lucky and that changes things for the better. Maybe not. So my advice is if you are going to try that, make sure to buy it from the local best buy so that you can return it easily. Alternatively, if Arny is so sure this will fix your problem, have him buy it for you and if it doesn't work, make it his problem.
Importantly, all HDMI repeaters like the optical device recommended, have the potential to cause HDMI incompatibilities. The cable is mostly used for the display/projector so likely has had little to no testing between your sources. If you can at all avoid these repeaters, you should. Speaking of display, that may also be causing your ground loop even though it is down stream.
The solutions I would offer would be the following:
1. Just live with it
. Don't put you ear next to the speaker. I know once you are aware of the noise it is hard to get it out of your mind but it is the cheapest and easiest solution. You don't listen to your speakers point blank so it may not be an audible problem.
2. Make sure it is hum. It might be buzz and noise. And if so, it has other causes. Many amps for example will have some residual amount of buzz/noise that become more or less audible depending on your speaker's sensitivity. They will not be dead silent. This noise will often come about when you turn on one of the inputs, i.e. select the Oppo, etc.
3. Try using a balanced transformer between the Integra and your amps. You can buy the cheap Rat Shack unit for a quick test. But if this is the fix, I highly recommend getting the Jensen isolators: http://www.jensen-transformers.com/iso_aud.html
. Remember, in this situation the transformer will be in the loop for all audio so you want it to be absolutely neutral, not kind of, not sort, not "good enough," not "this guy tested it on the Internet using his PC and thought it was good," and not, "let me ignore what the manufacturer says and assume it is much better." Get the right product for the problem and the industry standard is Jensen. What is also great that Jensen will provide free technical consulting. Call them and explain the problem and they will give you far better analysis than anything you have been told in this thread
. Sadly, you need that in this broken audio architecture....