Why none of us audiophiles still cannot completely get rid of the "hum" in this day and age?

[wwenze]

The first FFT plot that Amir usually posts already includes the amount of power supply noise that will reach the speakers.

Granted, it does not include common-mode shenanigans, but trying to come up with an agreed-upon standard for testing common-mode interaction is a fruitless affair, I'll just let FCC to let me be or let me be me.

My own Marantz PM6005 measures at -80dB relative to 2Vrms iirc. Already pretty poor by today's $400 amp standard. But theoretically inaudible.

I should point out that 13dB @ 1m - around the same as a good computer fan - is actually pretty audible in this context, since that is 31dB @ 12.5cm or whatever sticking the ear to the tweeter means.

 

[Blumlein 88]

Okay some Umik 1 measurements were done using the RTA in REW. I had a 45 dbSPL level at 60 hz. I had the fridge off, and the HVAC off. I turned various parts of my surround system off and that did not budge. I was really puzzled for a few minutes. I had the Umik on a sturdy table on the little tripod. I also had two computers on it and an audio interface. I had the 3 PS units sitting on the table plugged in. AH, hah I said. I wonder if the hum vibration from those is making it across the table into the tripod of the Umik.

So I unplugged those and that 60 hz dropped to 23 dbSPL with 120 hz about 10 db lower. It is late night here and pretty much no one's HVAC is running as it is 70 degrees (21 C). I suppose the 23 db SPL is from the house in general humming at 60 hz and it still showed a sharp peak at 60 hz and 120 hz. I was surprised the noise level is at 0 dbSPL at 300 or 320 hz and less at higher frequencies. This is with an FFT size of 256 k so that is part of it. Switched to 1/6th octave RTA you get a nearly flat level around 22-25 db SPL across the spectrum.

I turned on different parts of my surround setup starting with the subs and that did not budge. With the whole system back up, 23 db SPL so I'd think the level of the gear is at least 15 db lower than this. If it were any higher it would raise the 23 db SPL 60 hz level. I ran long averages and it just didn't change. So hum from the stereo is apparently less than 8 db SPL.

With the AC on, 60 hz was raised to 35 dbSPL with 120 hz still 10 db lower. Noise in general above 400 hz didn't change much.

The Fridge (without AC) was interesting. It raised the 60 hz hum about 5 db, no effect on 120 hz. It did create a good peak at 17 hz, 34 hz, 68 hz and 102 hz. The long part of my room corresponds to 17 hz so I guess it was shaking floor, room whatever and noise was resonating there. 64 hz was about 33 db so higher than the hum. 102 hz was somewhat lower. And I don't know about the missing intervals.

With both fridge and AC on hum was about 37 db SPL and the other 17 hz related noise. Didn't make much difference above 400 hz. That was still maybe 25-27 db SPL on a 1/6th octave RTA.

To check in case part of the system was switching off due to no input, I played a 35 db SPL 700 hz tone. With everything else in the house off, the 60 hz hum level didn't change at all. I did get some very low level stuff at 17 hz and 34 hz. These seemed to build slowly taking 20 seconds or so to show up. Maybe shaking of the floor by the speakers stimulating the room resonance?

In any case, maybe it satisfies some people who wanted measurements. I think @pma was one of those.

Again my system is connected with XLR cables throughout, except the Rhythmik subs have XLR to RCA cables from Monoprice.

 

[Holmz]

The first FFT plot that Amir usually posts already includes the amount of power supply noise that will reach the speakers.

…

But what does it mean when there a bunch of manufacturer people that complain that pin-1 is connected at the AP device?

 

[NiagaraPete]

I'd like to bring to all the audiophiles attention this problem. No matter how expensive and carefully set up your system is, you know the hum is always there given enough volume and no source active. Generally, it's a lot worse than that and we just agree to live with it. We are all such perfectionists, we can spend thousands of dollars for a Dac that can process 768kHz and replace our 384kHz Dac and yet we accept to hear the hum. I learned how electricity is really delivered to our homes from a video of Amir at the age of 50 (and I have an engineering degree) and what is grounding and why it causes the "hum" but even he didn't offer a solution to get rid of it. Is there no solution? If there's, why doesn't anyone do anything about it?

I don't presume any techincal knowledge on the matter so I might be all wrong but I hear the hum. I lived in 3 different continents in the last 30 years and used many different brands of gear. The hum was always there to a varying degree (from only audible if you press your ear to tweeter to always there unless there's music playing supressing it). Let's rebel and force electiricity companies or electronics companies or whoever is causing this to stop it.

I have no hum at any volume or source. That said I got rid of my turntable, tape, and CD player.

 

[thecheapseats]

Speaking as an old audio guy (66,) wasn't fiber optics technology supposed to have liberated us all from ground loops by now?

Hum definitely still plagues us. Even though my system is hum-free, it didn't get there without some effort, and I still hear it in video soundtracks from time to time. Audibly transparent Bluetooth would work. In the meantime, isolate your cable TV/internet/telecom drop with a transformer. It can work wonders.

audiophile or pro-audio, in my experience the issues can be location specific... after twenty-two years in one location/building (built 1941 in L.A.) - I moved out of california twenty three years ago to telecommute most of my work...

bought a much newer four year old home at that time, but it had a ufer a/c ground instead of the traditional 'to-code' ground of the old location (that had to be mitigated as well - but that's another story)... the ufer ground was inferior for my audio-work purposes and required some bolstering to get it right... after that, the studio audio system performed as it had before it was moved...

 

[pablolie]

I agree with those who say - "no hum" here. Not any other kind of residual noise (I am utterly allergic to it). And may I add even in the 90s it was not a problem for me. No one should tolerate hum or hiss, ever.

 

[egellings]

My system doesn't hum along with the music at all; I taught it the words.

 

[threni]

I heard a hum the other day, for the first time in years. I was using a laptop as it was being charged. Also, I was wearing headphones connected to an amp which wasn't turned on (the whole system was switched off at the mains; I thought I'd switched it on and I was waiting the 40-odd seconds my moOde box takes to boot). As soon as I switched it on there was the usual silence.

 

[Mr. Widget]

I agree with those who say - "no hum" here. Not any other kind of residual noise (I am utterly allergic to it). And may I add even in the 90s it was not a problem for me. No one should tolerate hum or hiss, ever.

It's pretty easy to have a hum and noise free system if you are running your standard fare dome based "audiophile" speakers with <90dB sensitivity.

When you have a multi-amped system with amplifiers directly connected to horns with 105-112dB sensitivity it requires electronics that have very high SN numbers or you will hear quite a bit of hiss and with all of the extra connections avoiding ground loops becomes more of a challenge.

That said, you can get it pretty darned quiet with some effort.

 

[OldenEars]

my cheap shit bt receiver dongle plugged into an extension lead, plugged into the mains running from my house to my garage produces 60hz hum. its a ground loop.

if i had the same hum from multiple different setups across multiple different countries and multiple different times, i'd try to identify the common factor, which would seem to be my ears. So maybe worth visit a hearing specialist just to check?

 

[dlaloum]

my cheap shit bt receiver dongle plugged into an extension lead, plugged into the mains running from my house to my garage produces 60hz hum. its a ground loop.

if i had the same hum from multiple different setups across multiple different countries and multiple different times, i'd try to identify the common factor, which would seem to be my ears. So maybe worth visit a hearing specialist just to check?

Ideally the whole system should be grounded via the ONE ground point (and when we say whole system, it includes the power line wiring in your house down to the earth stake!)

Wherever there are multiple competing paths to ground, there is trouble.... (and particularly when you have a mix of "floating" - ie: ungrounded - components, and grounded ones, and even more so if they are in different rooms with long cables ) - the more variance in the grounding resistance there is between differing parts of the system, the more likely you are to have hum.

 

[OldenEars]

Ideally the whole system should be grounded via the ONE ground point (and when we say whole system, it includes the power line wiring in your house down to the earth stake!)

Wherever there are multiple competing paths to ground, there is trouble.... (and particularly when you have a mix of "floating" - ie: ungrounded - components, and grounded ones, and even more so if they are in different rooms with long cables ) - the more variance in the grounding resistance there is between differing parts of the system, the more likely you are to have hum.

i only get the problem with my £2.99 bt reciever, ive not even tried using a different usb power adapter which might fix it. At some point i'd like a box with a ldac, coaxial in from my cd player but it can wait

really appreciate your reply

 

[TonyJZX]

its probably something wrong with your area electricity supply

i've had some crappy ambivalent equipment and never had an issue with hum

especially if youre mixing electrical formats somewhere down the chain... i was going from optical to the preamp and that was going xlr to the poweramp

i often wonder if buying native 240v equipment and using them in a 110v country was an issue and vice versa