Low level HUM, driving me CRAZY!

[salsdali]

What's the last place you left the keys?

So, what changed? Was there a time when you didn't have the hum?

If so, backtrack, what's the first thing you did after that and noticed the hum?

 

[HomerJAU]

It sounds like the hum is gone, or greatly reduced using RCA cables. I’m not sure there's any audible difference between using XLRs and RCAs. Mark could sell his XLRs I guess.

 

[gene_stl]

https://www.audiosciencereview.com/...understanding-grounding-in-audio-video.21360/

https://solahevidutysales.com/cvs_hardwired_series_power_conditioner.htm
https://solahevidutysales.com/pdf/powerconditioners/cvs.pdf
Sola quite literally wrote the book on power conditioning. Everything sold by the audio industry are toys and junk.
Tripp Lite also makes good ones.

https://www.tripplite.com/products/power-conditioners~23
In the past I have had a large 800 watt Sola Topaz power conditioner as well as an 1800 watt Tripp lite. The Tripp Lite was killed in a lightning strike which it successfully stopped. (Not garaunteed). I do have some FSR switch gear currently that has very good MOV and capacitive "protection" but no transformers.
The reason I don't recommend the stuff I have seen at audio stores and catalogs is that they are more likely to reduce transient response than to help any imagined problem whispered in someones ear by the audio store salesman. If you live out in the country at the end of very long above ground power lines that are struck by lightning frequently you should hang your entire house on an extra isolation transformer.

There are here and there needs and uses for such things but 99% of the ones you see in audio installations are a complete waste of money. Please note that I have used them and learned how to use and specify them correctly since the 1970s. There are a very few pieces of scientific equipment that actually benefit from them. (Such as Scanning Electron Microscopes , and Laser Scanning Optical microscopes and elderly spectrophotometers) They were used with photographic enlargers back in the day but that was mostly overkill too.

Modern Surge protectors can lower voltage spikes but do nothing whatsoever when the voltage sags. Ferroresonant transformers can boost the voltage when it sags and the transformer also isolates from the nasty AC line. I have seen audio gear that claims to do this but the transformer was way to small. Both the above mentioned units were very large and heavy. In spite of articles to the contrary and a vigorous snake oil business selling line conditioners at most locations in the USA there is no need to "solve" a problem that really doesn't exist. In the majority of cases they are snake oil.

https://www.realhd-audio.com/?p=6223
https://www.realhd-audio.com/?p=5659
https://www.audiosciencereview.com/forum/index.php?threads/parlor-trick-exposed.389/
http://archimago.blogspot.com/2014/02/

 

[MarkerB]

Nobody has suggested ground loop isolators? So cheap compared to many of the suggestions here, and they always solve my hum and noise problems. I'm serious here; I've wired professional recording studios.

Ground loops are created from the simplest of gear hookups, most commonly because the power safety ground is run through your power distribution, while the signal ground is run through your line cabling. That's two ground paths.

The one exception to a ground loop problem in your case, mentioned earlier, is a small chance it's a power supply capacitor in your power amp. This could be why you'd hear hum regardless of volume setting. It's easy to check, because if you disconnect all signal sources to the power amp, the hum would remain. Still... it's not as likely the problem.

Ground loop issues are special. Inline filtering will not fix them, because a filter won't change the ground paths. Changing cables will not fix them, unless you're cutting grounds on the cables (but don't unless you really know what you're doing). A power conditioner with or without a transformer will not fix ground loops, because they also do not change the ground paths.

You can buy audio ground loop isolators for cheap on Amazon (don't trust most of the negative reviews; most people don't know how they work). Install several of them on various parts of your signal path. When you've eliminated the hum, start removing them until you find the one or two culprits. After you've found the problem point(s) in your signal path, you might want to invest in higher-end ground loop isolators. There's a passive transformer inside, so they do reduce gain, and can affect frequency response and headroom. Most people wouldn't be able to hear the difference.

Instead of lifting the signal grounds, a dangerous person could also try lifting all the power grounds with many of those 2-to-3 power adapters we've all used since we were kids. Obviously you wouldn't hook up the little tab that's supposed to connect to the outlet screw. The problem with lifting power grounds is you'll be in violation of safety codes, and will be increasing the risk a of shock.

 

[quicksrt]

You did try listening through headphones or earbuds right? Speakers off or disconnected, headphones with music, and music paused?

 

[sbrom]

Tough, frustrating problem! I‘d suggest looking for mechanical/acoustic sources, as you continue your search for an electronic culprit. Especially since the hum level does not change with volume setting.

I have a Blu-ray player that coupled mechanically with its cabinet to create a loud hum. Drove me crazy!

Does any of your equipment have fans or moving parts?

I’ve also heard hum from my furnace, refrigerator, household exhaust fans, etc..... none dependent on volume, just as in your case.

You did say the room is dead quiet when all equipment is off, which would seem to eliminate some of these possibilities.

If possible check the hum frequency using a spectrum analyzer. Verify it is a 60Hz harmonic and not some unrelated frequency. Analyzer apps available for iOS and Android devices. It may be difficult to pick out the offending signal, might require averaging or too much sophistication for a phone-based app.

 

[MidiMagic]

Oh, have I had fun with hum over the years:

- Note that ground loop is usually a 60Hz problem unless there is an unwanted 120Hz hum field radiating from something.

- Usually 120Hz is a symptom of a failing power supply.

- One hum drove me nuts for three hours until I noticed the hum was there with all of the equipment turned off. Someone had hung an old synchronous-motor clock on the other side of the wall behind one speaker.

- In a balanced-line system. the direct box (a transformer used to convert an unbalanced instrument to balanced for the mixer) was placed next to the wall-wart power supply that powers the instrument. The two transformers happily coupled. Hmmmmm. So keep ground-loop preventing transformers away from power transformers.

- Lighting devices and dimmers can produce unwanted 120Hz fields. So can ceiling fans, fluorescent lights, discharge lighting, and some energy saving lights.

- Don't forget your computer and monitor. Those can be unwanted sources of all kinds of noises.

- Can you measure the hum frequency on the audio lines (my multimeter has a Hz position)? If not, look for a mechanical source for the hum.

- Turn stuff off one device at a time. Note which ones make the hum disappear.

- Disconnect cables one at a time. Note which ones make the hum disappear.

- There is an energy saving device that reduces your electric bill by changing the waveform that goes through the meter. These can cause unwanted noises.

 

[jlladuke]

This may/ may not be helpful, but wanted to share my experience. I know you said it wasn't DirecTV, but this isn't related to the box itself. Had similar very annoying issue several years ago with the DirecTV device shown below. It was causing a hum for all channels, and I believe it was happening for all sources. I'd check to see if your DirecTV installation includes one of these devices. I believe it's a wifi repeater/ extender used to connect the DirecTV mini genies to the main one. When I removed that, all hum went away, and DirecTV still functioned properly in all rooms in the house.

 

[Sonik Wiz]

@gvl_guy went through a similar maddening situation with noise & hum. Turned out it was his WiFi router. He turned it off & off went the noise. I think he just relocated the router & all was good.

 

[marpow]

Thanks for all your help. I thought I was alone with this but seems like everyone has experienced noise in there rigs. In the end I am satisfied with the switch from XLR's to RCA's. I cannot give you a reason as to why they work differently in my case, I would of thought going from RCA's to XLR's would have made more sense? I would love to know the answer.

I have to let go for awhile and see what if any sound difference there is. I definately like it so far but there is a lot of different music to listen to.

Yesterday I disconnected EVERYTHING AGAIN put back one at a time, switched cables one at a time.
Without boring you with every detailed thing I did (trust me I did it all) I could only come up with the RCA's as the answer, thank God someone suggested that as I wouldn't have tried that on my own.

NOW my second problem:
This does not bother me as much but is still a pain. I have a dedicated PC Fanless that is power/ethernet connected, USB out to my external 6 channel DAC, RCA's out to 7.1 section in of my pre/pro, no problems so far. JRiver is my player. Beeen this way for years.
I have recently been able to rip and play Atmos music through the video section of my JRiver player, works great.
I order to do this I must go HDMI out into an HDMI in of what I picked the Aux zone of pre/pro. Works great.
The second that HDMI touches the pre/pro I get a tapping in my sub closest to the PC, it sounds kinda like a morse code signal, low level does not increase with volume. My sub has its own outlet, RCA LFE cable grounded at both ends, speakon high frequency cable.
If I am not listening to Atmos, I just pull HDMI out from PC and gone is problem.
There must be an answer to this, I was thinking about calling the PC company and asking them.

 

[audiomaster]

If you ran Room Correction, your Pre-Pro set the crossovers. You can go in and manually change them. I’d suggest 80 or 90 Hz.

Normally hum is at 120 Hz or maybe 60Hz. Be nice to put a scope on it and see. Or is it a "BUZZ" with some higher frequencies mixed in?

Be interesting to see what changes if you can move crossover above 120Hz as a test.
Also do you have hum with nothing connected to your power amp and the inputs shorted? If so the problem has to be in the power amp, probably in the power supply. And if it has a three prong plug, lift the ground with a 2-3 prong adapter and see what happens.

 

[marpow]

Normally hum is at 120 Hz or maybe 60Hz. Be nice to put a scope on it and see. Or is it a "BUZZ" with some higher frequencies mixed in?

Be interesting to see what changes if you can move crossover above 120Hz as a test.
Also do you have hum with nothing connected to your power amp and the inputs shorted? If so the problem has to be in the power amp, probably in the power supply. And if it has a three prong plug, lift the ground with a 2-3 prong adapter and see what happens.

I went through the different crossover settings, and could find no help in the hum department, ended up setting ALL to 80hz.
When I turn on amps only there is zero noise. Only when adding in pre/pro. My unit doesn't like XLR's, I have no idea why.
I did so many 2 prong adapter tests, 15 to be exact.
I don't own a scope, or know how to work one.
Satisfied for now with the RCA's.
The question for now is sound, is there a noticable sound difference in my new RCA's vs my old XLR's, that will take me a few days to really know, so far so good.
It is really sad to look at all those XLR's, thats a lot of bread, man.

 

[audiomaster]

Thanks for all your help. I thought I was alone with this but seems like everyone has experienced noise in there rigs. In the end I am satisfied with the switch from XLR's to RCA's. I cannot give you a reason as to why they work differently in my case, I would of thought going from RCA's to XLR's would have made more sense? I would love to know the answer.

I have to let go for awhile and see what if any sound difference there is. I definately like it so far but there is a lot of different music to listen to.

Yesterday I disconnected EVERYTHING AGAIN put back one at a time, switched cables one at a time.
Without boring you with every detailed thing I did (trust me I did it all) I could only come up with the RCA's as the answer, thank God someone suggested that as I wouldn't have tried that on my own.

NOW my second problem:
This does not bother me as much but is still a pain. I have a dedicated PC Fanless that is power/ethernet connected, USB out to my external 6 channel DAC, RCA's out to 7.1 section in of my pre/pro, no problems so far. JRiver is my player. Beeen this way for years.
I have recently been able to rip and play Atmos music through the video section of my JRiver player, works great.
I order to do this I must go HDMI out into an HDMI in of what I picked the Aux zone of pre/pro. Works great.
The second that HDMI touches the pre/pro I get a tapping in my sub closest to the PC, it sounds kinda like a morse code signal, low level does not increase with volume. My sub has its own outlet, RCA LFE cable grounded at both ends, speakon high frequency cable.
If I am not listening to Atmos, I just pull HDMI out from PC and gone is problem.
There must be an answer to this, I was thinking about calling the PC company and asking them.

What happens if you take a piece of single conductor wire and touch it to the chassis of both units at the same time instead of the HDMI cable? Could be a ground loop in the HDMI connection?

 

[marpow]

What happens if you take a piece of single conductor wire and touch it to the chassis of both units at the same time instead of the HDMI cable? Could be a ground loop in the HDMI connection?

I'll give that a try, thank you.

 

[audiomaster]

I went through the different crossover settings, and could find no help in the hum department, ended up setting ALL to 80hz.
When I turn on amps only there is zero noise. Only when adding in pre/pro. My unit doesn't like XLR's, I have no idea why.
I did so many 2 prong adapter tests, 15 to be exact.
I don't own a scope, or know how to work one.
Satisfied for now with the RCA's.
The question for now is sound, is there a noticable sound difference in my new RCA's vs my old XLR's, that will take me a few days to really know, so far so good.
It is really sad to look at all those XLR's, thats a lot of bread, man.

Normally in professional studios or systems, the shield of the XLR cable (pin #1) is only connected at ONE END!. Usually the end at the input of the device. This still provides a grounded shield without the possibility of a ground loop in multiple connections or noise currents flowing in the shield. If you have a meter, see if pin one is connected at both ends. If so and you can cut the pin one connection at all of the female XLRs that may solve your problem.

 

[marpow]

Normally in professional studios or systems, the shield of the XLR cable (pin #1) is only connected at ONE END!. Usually the end at the input of the device. This still provides a grounded shield without the possibility of a ground loop in multiple connections or noise currents flowing in the shield. If you have a meter, see if pin one is connected at both ends. If so and you can cut the pin one connection at all of the female XLRs that may solve your problem.

I don't have a meter, but very intersting.

 

[jimfisheye]

Separate amplifiers but it's in everything? Yes.

What happens when you only power up one amp at a time? Same.
ie. Will one power on by itself hum free? If amp powered on ONLY, no noise, so that tells me it is pre/pro?

It is still there with inputs disconnected? (Sorry if already answered.) Yes. I have disconnected ALL input devices, only leaving Pre/Pro and 2 channel amp and two speakers, exactly same hum, just less speakers and amps.

Looks like you are chasing ground loops now? That's likely what's going on.

I was trying to get at isolating everything to help go straight to the issue.
I don't quite follow "If amp powered on ONLY, no noise" vs "I have disconnected ALL input devices, only leaving Pre/Pro and 2 channel amp and two speakers, exactly same hum"

Again, sorry for jumping in and maybe not reading everything!

Test all amplifiers one at a time with nothing connected to the input.
Then test the amps one at a time with the normal thing connected to the input. (I guess this is one set of outputs from your crossover unit?)

The amps by themselves with no input connected. (Speakers still connected though!)
If they still hum, then it's something getting into the amp itself through power.
If not, then it had to be coming into the input.

Next, trying different inputs.

If you find a single device that hums when you plug it into any amp, then there it is.

If your normal input device (ie the output from your crossover or audio interface or AVR or whatever) is hum free by itself...

Now start with the connections to multiple amps.
If THIS is where the ground hum starts, you have ground loop issues!

This is where you may get into the stuff like lifting the shield on one end of the cable. (Only applies to balanced cables!)

Are the connections between preamp to amp, interface to amp, or crossover unit to amp balanced? (whichever it is or if all of the above) If balanced connections are an option, they're really your friend for this kind of stuff. If you're dealing with a unbalanced device in there (rca jacks only), I know where I'd be pointing my finger first.

 

[audiomaster]

I don't have a meter, but very intersting.

How many thousands do you have in your system? And you don't have a simple volt-ohm meter? Probably get a simple one for less than one of those XLR cables!

 

[marpow]

How many thousands do you have in your system? And you don't have a simple volt-ohm meter? Probably get a simple one for less than one of those XLR cables!

Easy now. Not every race car driver knows how to work on there car.

 

[jimfisheye]

Wait... is the "Pre/Pro" an amplifier or a device? (Maybe your crossover unit?)

I thought it was one of your amps when first reading that. Again, sorry if I missed a post!
Sounds like you may have found the issue?

But if it works by itself and only hums when other stuff is connected - and that other stuff also works by itself - then you have a ground loop messing with you.