2. amps-preamps
  3. 189007-102228

Audible High Pitched Hum... Advice Needed

I have an odd issue that I can’t quite wrap my head around. As the title suggests, I’ve been fighting a high pitched hum in my system and I believe that I’ve found the source but I’m looking for some solutions. I have a complicated system so let me start with a description.

I have a combined 2 channel and home theater setup. Starting with the two channel sources, I have a Mofi ultradeck turntable feeding a Parasound Jc3 jr phono pre and I have a Lumin T2 streamer/dac all feeding a Simaudio I-5 integrated amp and a pair of Kef LS50s. This amp also has a HTB input that I feed from an Emotiva XMC-1 to power my speakers for home theater. I have my TV which is a LG C3 connected to my XMC-1 via HDMI ARC for home theater. Everything is connected to a Furman Elite 15pfi power conditioner on a single duplex. I have the turntable, phono pre, and the streamer grounded together via their respective grounding posts. I have no options to ground the I-5 or the XMC-1. I’ve got things connected single-ended at this point but I have tried balanced out from each the phonopre and the streamer to a TVC passive volume control that I have to convert the signal and I still have the same hum behavior described below.

Okay now thats out of the way, this hum is constant no-matter the volume and is only present when the TV, Emotiva, and I-5 are powered on in my home theater setup with the I-5 input set to HTB. I’ve isolated the hum to the input from both my phono pre and my streamer. If either of those two pieces of equipment are plugged into power and the I-5, I get the hum. It doesn’t matter if those units are powered on or not, the hum is still present. However if I leave everything plugged in and I disconnect the power cords for the phono pre and the streamer - hum disappears. Or - if I change the I-5 input from the HTB to any other input - hum disappears. The hum also travels through both channels even if only a single RCA cable is plugged in. This leads me to think that I’ve got some type of ground issue through the XMC-1 that is exciting something in the unit. The hum doesn’t sound like a ground loop to my ears although I’ve only listened to one online.

Another piece of evidence that leads me to think its ground related is I have my PC plugged into the TV directly for gaming. I get really horrible coil whine from my graphics card leaking through the system but only with the phono pre and streamer connected. If I disconnect those - you guessed it - hum gone. I hear some really strange sounds when I simply touch the HDMI cable from the PC to the contacts in the TV that pass through the system even without the cable being completely plugged in. I was thinking that maybe some DC from the computer power supply could be the culprit.

All that being said - my cabling is pretty tight behind everything but I’ve done my best to move signal cables away from power cables. The hum does not change if I shift my signal cables around. All of my interconnects are high quality from DH labs or Bluejeans. I’ve done some research into DC offset but I don’t think I have that issue as the sound is 100% coming from my speakers.

Any thoughts would be greatly appreciated! I’ve done my best to describe everything I can think of but I’m happy to share any additional details. I can live with unplugging things to eliminate the hum when I’m watching TV or a movie but it really defeats the purpose of having a combined system.

ajnackman
ellajeanelle's avatar
ellajeanelle
386 posts
 

Why don’t you add an AC switch between your power source and the component/s that are causing the issue when not in use?

Those noise issues can be difficult to solve and a process of elimination is the only sure way to pinpoint it. Not the ideal solution but have you tried an inexpensive inline filter? These worked for me when I had a similar issue with a secondary system years ago. The buzz was of the type you described.  I was actually surprised they worked so well considering the cheap price.  If they don't work for you just send them back. Use them on the input side. I bought a few from Amazon.

MEIRIYFA Car Stereo Audio Filter Suppressor, Car Amplifier Noise Filter Isolation 2RCA Male to Female for Car Power Amplifier, Studio Recording Equipment

 

ajnackman OP
60 posts
 

What about a product like this? This is just going to add up as it will double my interconnects. I wonder if introducing this between the XMC-1 and my I-5 will solve the issue. I suppose I can always start with 1 and see how it goes.

 

https://www.markertek.com/product/il-stereo-19/sescom-il-stereo-19-pro-audio-hum-eliminator-2-channel-rca-hifi-style-stereo-isolator-transformer-coupler?gad_source=1&gclid=Cj0KCQjwwMqvBhCtARIsAIXsZpY6JsUWaeLGJ80YbAEqhtm1V3b-iiaN8O9z1LKseD2fyeXrNtD_dcgaAhXvEALw_wcB

 

Here's another more expensive option - not sure of the difference.

 

https://www.fullcompass.com/prod/036365-jensen-transformers-ci-2rr-stereo-2-channel-audio-input-isolator?gad_source=1&gclid=Cj0KCQjwwMqvBhCtARIsAIXsZpaACb3K2voGDtniND9HPr_w18_TfFSMtcyNPJMhLVeoPcEuTRLgJjUaAmoKEALw_wcB

ellajeanelle's avatar
ellajeanelle
386 posts
 

I don't see why that would not work.  Seems like better quality and probably does the same thing but I'd see if Amazon has one just because of the easy returns in case it doesn't solve your problem.

erik_squires
16,130 posts
 

So you are aware, HDMI is notoriously noisy and prone to causing ground loops, ESPECIALLY from PC's.  PC's are just prone to ground loops in general but HDMI seems to also be bad.

Any coaxial cables coming into the HT can also be suspect.  The test in all cases is to turn on all devices but disconnect the suspected cause of the humm. When it vanishes you have found the problem.  It's of course not usually just 1 item sometimes it's two.  That is, sometimes it's 2 different devices which cause the humm.

The ideal and relatively inexpensive solution, whether your problem is HDMI or coaxial is a ground loop isolator.  In the case of a laptop, another test is of course pulling the power adaptor out of the wall, but that's not often very useful except as a proof of concept. 

More to discover