Subwoofer hum when HDMI video out is connected - Onkyo TX-NR1009

OldiesButGoodie

Standard Member
I have a significant hum coming from the subs in my system (I have two Emp Tek 1010is, but it happens with any sub I connect, I have several others). The hum starts whenever the HDMI cable going out to my TV or projector are connected (and either display is on). Any suggestions or ideas? I have tried pretty much everything, but I am open to all ideas (I have not tried replacing the receiver - that would be a pain I woud want to avoid if I can).

Thanks in advance for your help!

OBG
 

goujam

Well-known Member
I have a significant hum coming from the subs in my system (I have two Emp Tek 1010is, but it happens with any sub I connect, I have several others). The hum starts whenever the HDMI cable going out to my TV or projector are connected (and either display is on). Any suggestions or ideas? I have tried pretty much everything, but I am open to all ideas (I have not tried replacing the receiver - that would be a pain I woud want to avoid if I can).

Thanks in advance for your help!

OBG

Sounds like a grounding problem are all the devices plugged into thr same socket. So share the same extension ?
 

OldiesButGoodie

Standard Member
I have many components (and Bob Carver tube monoblocks :clap:) so they are running on two separate dedicated 20A circuits, each circuit on a different phase, each fed to serate Monster power centers. I do not think it is a grounding issue at this point given everything I have done to test and prevent that (tried lifiting the ground systematically, etc.). Here's one other pice of info I discovered yesterday after I wrote the post:

The cable video is coming from a Motorola QIP7100 1 box (Verizon FIOS). If I go into the settings for audio and set the volume to "variable" and then go to "box volume" and set it 0, the hums virtually disappears (of course, I also get no sound transmitted to the AVR receiver over HDMI). One idea that I would like to explore is forcing the Motorola box to use HDMI for video and then get the audio from optical. Not sure if the Onkyo receiver will allow that, but I will try anyway.

Hum can drive you insane!:censored:
 

goujam

Well-known Member
I have many components (and Bob Carver tube monoblocks :clap:) so they are running on two separate dedicated 20A circuits, each circuit on a different phase, each fed to serate Monster power centers. I do not think it is a grounding issue at this point given everything I have done to test and prevent that (tried lifiting the ground systematically, etc.). Here's one other pice of info I discovered yesterday after I wrote the post:

The cable video is coming from a Motorola QIP7100 1 box (Verizon FIOS). If I go into the settings for audio and set the volume to "variable" and then go to "box volume" and set it 0, the hums virtually disappears (of course, I also get no sound transmitted to the AVR receiver over HDMI). One idea that I would like to explore is forcing the Motorola box to use HDMI for video and then get the audio from optical. Not sure if the Onkyo receiver will allow that, but I will try anyway.

Hum can drive you insane!:censored:

Yeah your onkyo will allow you to assign a optical input to a HDMI video
 

OldiesButGoodie

Standard Member
I have a new tip to ad that worked to some degree in my HT. They are mentioned elsewhere in the web. The hum seemed to be most connected with m cable box - specifically the coax feed. I used to 75-300 ohm transformers connected back to back to isolate the cable line ground from my system (so go 75 to 300 and 300 back to 75 ohm). Make sure the transformers are not autotransformers - take a continuity checker (VOM) to the store and make sure the 75 ohm side is not connected to the 300 ohm side in any way (this saved me at Radio Shack - a web-recommended part number had been changed to an autotransformer and would not work). Spent 7 bucks - works.

I sill have some leftover hum but at this point I suspect it is a faulty Onkyo sub and pre-outs. Will have to buy a separate receiver to test.

Thanks!
 

Mark.Yudkin

Distinguished Member
If using a pair of baluns back-to-front helps, (i.e. if it's cable and not!!! satellite), you can completely eliminate the hum by using a bespoke cable coax ground loop filter, such as this or this, as appropriate to your cable plug type. Also, you can eliminate the Onkyo and subs as being totally innocent in every respect.
 

Mark.Yudkin

Distinguished Member

OldiesButGoodie

Standard Member
I just ordered a Jensen Sub1RR filter as well. Seems like they are the top dogs in this category, and it is stupid to have thousands of dollars in speakers, amps etc. hobbled by a cheap filter. Will report on how each of these tweaks helps or doesn't.

OBG
 

Mark.Yudkin

Distinguished Member
I just ordered a Jensen Sub1RR filter as well. Seems like they are the top dogs in this category, and it is stupid to have thousands of dollars in speakers, amps etc. hobbled by a cheap filter. Will report on how each of these tweaks helps or doesn't.

OBG
You should not need a SUB-1RR if you solve the cable TV feed. All filters have some effect, the better the transformer, the less deterimental it is. Jensen publishes their figures, which is one of the reasons for their excellent reputation, but not using an unnecessary filter is still the best solution.
 

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