Tripp Lite isolation transformers

Sounds like a ***** eric. What's the problem? Have you isolated it to a particular device or two?

Kind of. I it seems to be a couple of combinations of various components, but mainly revolving my HTPC and cable box. I also get a very low level hum from my sub amps, hardly noticable unless the sound is off and my ear is next to the driver.


I have one optical input so I 'solved' the cable box issue by using it. I lifted the ground on the HTPC (temporarly) and all was good.


I have one HDMI (video only) on my plasma so I purchased a passive switch from monoprice. When I connect the DVI-HDMI cable to the switch the hum returns, so I assume the plasma is another issue. I may unplug the plasma later to confirm.

Can you isolate this to whether it's audio cable connections or video cable connections, both...? Try it without lifting the ground on the HTPC. Also, FWIW, have you checked all your outlets ($4 tester at HD) to ensure they all are wired correctly? All devices hooked up to the same circuit or different ones? Got a multimeter? If so, and it's possible, can you measure the resistance between the grounds of closely spaced outlets?

Thanks Chu Gai. I'll pick up a tester and check this weekend.

The triplite isolation transformer will not prevent ground loops because it does not break continuity with safety ground - the catalyst for all ground loops.

Quote:
Originally Posted by ericgl /forum/post/0


I also get a very low level hum from my sub amps, hardly noticable unless the sound is off and my ear is next to the driver.

Click to expand...

this level of noise is normal and is a result of a gain set too high somewhere in the signal chain. e.g. you might try reducing the gain on your sub and increasing the .1 channel gain on your a/v receiver/pre-pro if the former was set much higher than the latter.



Quote:
Originally Posted by sprung2 /forum/post/0


The triplite isolation transformer will not prevent ground loops because it does not break continuity with safety ground -

Click to expand...

Of course your right, it can't and still provide a ground. Thanks.


I just realized there is a possible path between the chassis' of my amps and HTPC, could this be an issue?

With ground loops you just never know sometimes. What sort of path are you talking about?

Both sit on an an aluminum rack, rods spaced maybe an inch apart. I don't know if the components are sitting on their rubbber feet or not, or if the AL is coated.


It won't be a big deal to set the PC on a dielectric to see if this helps.

Well, you've got some work cut out for you eric, that's for sure. If you find that you're just striking out, you just might find that the products at ebtechaudio.com might work for you. For example, if an audio connection is the one causing the hum, their HumEliminator might be worth investigating. You should be able to find their products at most pro audio shops like Guitar Center. Unless things have changed with them, you should have no problem returning the item if you strike out. On another forum, I suggested that product to a person who had a problem with a fridge that would induce noise into a person's system. Inserting it between his amp and pre/pro did the trick. I imagine there are probably other similar devices so you might want to ask the salespeople there.



Quote:
Originally Posted by ericgl /forum/post/0


Of course your right, it can't and still provide a ground. Thanks.


I just realized there is a possible path between the chassis' of my amps and HTPC, could this be an issue?

Click to expand...

Yes, If your amps are grounded (3 prong plugs) then their chassis' are bonded to the ground conductor.


Chu's suggestion is good. But you can go the same route as you did with your cable by using a digital audio switcher