Low level HUM, driving me CRAZY!

[quadsearcher]

Trying think outside the box here, I'm unclear if you tried just one two channel amp into a pair of speakers. No Pre, just an amp and speakers. Make sure everything else is unplugged from wall AC. If hum persists try just an amp and no speakers. If OK, try with each amp separately. Only add sub after all else is checked, and after all speakers added back one at a time, then Pre.

Could it be acoustic noise (like transformer noise)? Low level sound can bounce around and be hard to know where it is exactly coming from.

When setting up to record with a microphone specialist, it took a long time to isolate that last hum when electronics, fridge, etc, were off. I'm talking so low it wouldn't be heard unless a recording of silence was turned up loud.

 

[4-earredwonder]

I hate to see my pal Markie going through such AGITA. My advice: take a break ... ride your bike get some air and try contacting a B&W rep tomorrow. There's one located in Hayward, California....phone number: 650~569~1267. Perhaps they can enlighten you on the pros and cons of bi~wiring, etc. If not, maybe they can direct you to the proper troubleshooting source.

Worth a try, BUD! And it wouldn't hurt to down a Jack and a BUD!

 

[DuncanS]

I have a 120Hz hum/buzz

In the US you have 60Hz mains, when you rectify that in the first stage of a power supply (PSU), so straight after the mains transformer, you get a 120Hz waveform, which is then smoothed via large electrolytic capacitors to give DC, this then feeds the individual power supplies for the electronics. So if that first stage electrolytic capacitor is failing it will let through a constant level 120Hz. OK it does depend on the type of power supplies used in your system, and if is is coming out of all channels at the same level it will most likely be in the unit driving them, I am also assuming the hum is there no matter which source you select.

 

[markshan]

My lighting is only one lamp on stand, no overhead lights.

Incandescent or fluorescent? Have you tried unplugging it for a minute?

 

[markshan]

I generally do not recommend power conditioners, but if it is a problematic ground loop, a conditioner that has in it an isolation transfomer can block ground loops. But if you have a bad filter cap in the power supply none of these solutions will do anything. Then it needs to go onto the service bench.
If you decide to try a power conditioner get a real one from Sola or TrippLite , not one from a hifi source.

Why?

I have had great success using Furman power conditioners that are marketed for pro sound.

 

[Tornado Red]

I know you've replaced cables, but what about spraying contact cleaner on the cable/port when unconnected? Also, any bare speaker wires that could have a stray copper strand touching a neighbouring connection? Speaking of lighting, I had an issue a few years ago with halogen pot lights on a dimmer in my music room. I changed the bulbs to LEDs and the older dimmer did NOT like the LED bulbs and had to change it to a more modern one, which is pretty common apparently. Lots of buzzing going on while I had the old dimmer.

 

[4-earredwonder]

Why?

I have had great success using Furman power conditioners that are marketed for pro sound.

I likewise have had GREAT SUCCESS with both power conditioners and upgraded power cords. Transformed my system.

 

[edisonbaggins]

I know you've replaced cables, but what about spraying contact cleaner on the cable/port when unconnected? Also, any bare speaker wires that could have a stray copper strand touching a neighbouring connection? Speaking of lighting, I had an issue a few years ago with halogen pot lights on a dimmer in my music room. I changed the bulbs to LEDs and the older dimmer did NOT like the LED bulbs and had to change it to a more modern one, which is pretty common apparently. Lots of buzzing going on while I had the old dimmer.

My dimmer post in my music/YouTube room buzz. Drives me bonkers. If I can replace the bulbs and switch, and leave the pots I'll do it!

 

[J. PUPSTER]

Mark, I believe Garry ( @HomerJAU ) has speakers like yours, perhaps he can weigh in on some of this...

 

[marpow]

Incandescent or fluorescent? Have you tried unplugging it for a minute? Incandescent, been unplugged from wall all day while I experiment.

 

[HomerJAU]

@marpow Do you have and XLR to RCA cables in your system? I had hum when I bought my two recent power amps with XLR inputs.I bought XLR to RCA cables as my processor has RCA outs only. The cables were the problem. I needed to disconnect the earth at the XLR end to fix.

 

[Tornado Red]

My dimmer post in my music/YouTube room buzz. Drives me bonkers. If I can replace the bulbs and switch, and leave the pots I'll do it!

I believe my lights had GU10 halogen bulbs. There is an LED replacement for these which I bought, mostly for lower energy consumption. The newer dimmers should have 'works with LED bulbs' on the packaging someplace.

 

[marpow]

It seems when I switch from XLR to RCA there is a significant improvement. I am not educated enough to say why.
When I read, RCA is a single power wire wrapped by ground shield, XLR are two power wires wrapped by ground, as the signal passes through XLR, they reverse at the end (right/wrong?) which supposedly cancels the noise?
Hey if I improve with RCA's that is good enough, sort of what @HomerJAU was saying?
B&W's don't like XLR's ?
I have put all back together except my 3 subs, going to do that now. I have everything much more tidy than it was, not that really makes a difference. No power cables and no speaker/interconnects are touching/running parallel, when they do come close it is like a +.
I was short two RCA's, center speaker and two heights, so they are still XLR's.

I got stressed so my tinnitus is acting up, geez, probably hear buzzing in heaven or hell, wherever they got me pointed.

 

[HomerJAU]

XLRs have a separate earthed shield (The major benefit). But the cable shield is earthed at both ends which can cause an earth loop current to flow in the cable if your devices at each end are not earthed to same point. This earth loop current causes the hum. It doesn’t alway occur, it depends on each device’s internal wiring of the XLR socket and electronics. (That’s the gist of it, as I remember/understand the issue)

 

[Steve Schoultz]

It seems when I switch from XLR to RCA there is a significant improvement. I am not educated enough to say why.
When I read, RCA is a single power wire wrapped by ground shield, XLR are two power wires wrapped by ground, as the signal passes through XLR, they reverse at the end (right/wrong?) which supposedly cancels the noise?
Hey if I improve with RCA's that is good enough, sort of what @HomerJAU was saying?
B&W's don't like XLR's ?
I have put all back together except my 3 subs, going to do that now. I have everything much more tidy than it was, not that really makes a difference. No power cables and no speaker/interconnects are touching/running parallel, when they do come close it is like a +.
I was short two RCA's, center speaker and two heights, so they are still XLR's.

I got stressed so my tinnitus is acting up, geez, probably hear buzzing in heaven or hell, wherever they got me pointed.

If you’re grounded on both ends of the XLR cables this a ground loop. You only need to ground one end of the shield.

 

[HomerJAU]

Here's a long write up on the subject:

https://reva.blob.core.windows.net/mmh4/PDFs/AN_Legacy_pin_1_problems.pdf

 

[marpow]

If you’re grounded on both ends of the XLR cables this a ground loop. You only need to ground one end of the shield. How would I know Steve? they are just store bought AudioQuest XLR's.

 

[marpow]

Here's a long write up on the subject:

https://reva.blob.core.windows.net/mmh4/PDFs/AN_Legacy_pin_1_problems.pdf

I will read Garry.

 

[marpow]

Done for day, all put back, made some progress, but that was 8 hours of fiddling, one cable at a time, whew.

 

[Steve Schoultz]

The shields in the XLR cables are terminated on both ends of the cable at pin1. The most likely problem is how pin 1 is grounded internally in the preamp/amp. If there is any difference in ground potential, there is where the ground loop can occur. For instance the pin 1 is attached to circuit ground in one device and chassis ground in the other device. You can open the connector on the amp end and remove the the shield to pin 1 connection. There are other solutions such as an isolation transformer. I really hate to give you advice and wouldn't want you to damage your equipment.