Switch to Optical HDMI due to HTPC interference

neo_2009

Well-known Member
My only source is an HTPC that is located in a different room, and connected to the AVR (NAD T758V3, in a 5.2.4 configuration) by a 3M Monoprice HDMI premium cable. To provide power to the remaining 2 Atmos speakers, i'm using a class D HPA D500.

Prior to using the HTPC, i was using a Zidoo X8S, and everything was smooth, no pops, no interference.
As soon as i switched to the HTPC, i began having a strong interference between the HPA D500 and the HTPC, to the point i had to remove it from the system, and downgrading to a 5.2.2 configuration.

I have all speaker cables, power cables, etc, as isolated as possible in separated gutters.
I also tried using ferrite ring's in the HDMI cable, interconnects, all to no avail.

I'm 100% sure that the problem is indeed the HTPC, and more specifically the HDMI cable that connects the HTPC to the AV, given that if i remove the HTPC, the interference disappears.

I'm tempted to try a 3M optical HDMI cable, as they should be imune (??) to interferences, and may be able to resolve this problem!

Any ideas if this might work, and any suggestion for an HDMI optical cable?
 

Jamie

Distinguished Member
It's worth moving your HTPC to the same room and powering it from the same outlet. A common cause of noise like this is a ground loop from having equipment connected on separate sockets.
 

neo_2009

Well-known Member
Thank you for the advice, but it's already being powered by the same outlet.
I run an extension and all power cables are powered by the same outlet.
 

Otto Pylot

Active Member
How long is your run? And what exactly do you mean by interference? A hum, pq issues?
 

neo_2009

Well-known Member
It's a very loud Hum, that starts as soon as i turn the HPA D500 on.

No changes in PQ.

Please note that there was no Hum with the exact same configuration, but with the Zidoo and without the HTPC.
 

Otto Pylot

Active Member
Ah. That does sound like a grounding issue as mentioned above. FWIW, I have all of the components to both of my HTS's connected to UPS's. So, you didn't say how long your cable run is and what you are trying to push.
 

neo_2009

Well-known Member
The AVR and the HPA are in the cinema room, while the HTPC is in as adjacent division.

This adjacent division has the HTPC, a subwoofer amplifier and a NAS.

Through the wall, there are 3 holes, the first one for a 3M power outlet extension (the outlet is in the cinema room), to provide power for the above gear; the second one for the subwoofer speaker cables and an RCA to XLR Y cable, to connect the AV to the subwoofer amplifier, and the third for the 3M HDMI cable.
 

neo_2009

Well-known Member
Given that only when the HTPC is connected by HDMI the Hum appears, it seems to indicate that the noise is being transported by the HDMI cable, and somehow picked up by the amplifier.

If i disconnect the HDMI cable, the hum disappears.
 

Otto Pylot

Active Member
What is the HDMI cable length? That makes a difference as to what kind of cable may work and if you are pushing HDMI 2.0 4k HDR or HDMI 2.1 for gaming. Hybrid fiber cables work very well but they have a fiber core surrounded by copper wiring (used for communication like ARC, EDID, HDCP). It sounds to me like you need to either fix or replace the HTPC and your existing HDMI cable is fine. Is the cable a certified, Premium High Speed HDMI with the QR label or is it just a generic HDMI cable. It could be that a better made passive cable may work (better insulation/grounding) but I kind of doubt it.
 

Otto Pylot

Active Member
Its a 3m Monoprice Certified Premium HDMI 28 AWG cable:
Amazon product
If the cable truly is a certified, Premium High Speed HDMI cable (exact wording) it will come with a QR label of authenticity on the packaging. The product description says it is certified by an ATC but it is offered in lengths up to 30' and certification is typically up to 25'. And I don't see the QR label in the product description. There are a few 30' ATC certified cables but are not easily found. Keep in mind that the QR label is key.

Monoprice is a reseller. They do not mfr their own cables, nor do they have the resources to validate every cable mfrs claims. They depend on the supplier for accurate, true information.

Keep in mind that certified PHS HDMI cables are a bit stiff because they are passive cables. That being said, make sure that your cable connection does not have any sharp, 90º bends, and that there is no strain on the HDMI ports.
 

Joe Fernand

Distinguished Member
AVForums Sponsor
You could try a Fibre HDMI cable (not Hybrid Fibre with this issue) to try and electrically isolate the HTPC from the AVR - though you have to wonder why the HTPC is so noisy.

Is the HTPC properly grounded?

Joe
 

neo_2009

Well-known Member
I think the plug is grounded, and it uses a Seasonic Focus Gold.
I will try to dig a bit more on that end.

Regarding the Fibre HDMI cable, do you have any suggestion?
Thank you!
 

Joe Fernand

Distinguished Member
AVForums Sponsor
The New 10m and 20m cables from HDFury are proving to be very easy to integrate with systems where other cables have caused problems.


Joe
 

neo_2009

Well-known Member
The cable seems reasonably priced for a high quality 10M cable.

But 10M is away too much, i just need 3M.

Is 10m the minimum length?
 

Joe Fernand

Distinguished Member
AVForums Sponsor
It makes no real difference in terms of cost if you go 3m or 10m - the cost is in the electronics and the assembly.

It is a very thin and flexible cable you can easily hide it away.

Joe
 

Otto Pylot

Active Member
@neo_2009 I would pursue the suggestions by @Joe Fernand. If you can, it might be a good idea to test out the fiber only cable if you go that router before you install it. It really does sound like the HTPC and grounding.
 

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