Arrrgggghhh! This hum is driving me mad!!!

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NerineNerine Frets: 1244
Will try to keep it brief. 

Guitar/amp plugged in downstairs. 

Volume on guitar up. Guitar just resting against the couch. 

No hum. 

Turn on computer upstairs. 

Lots of electric hum and buzz from amp downstairs. 

Bring computer downstairs. 

Set computer up next to amp. Different socket, mind. 

Turn on computer. No or negligible hum. 


Tried three different sockets upstairs. Same deal. Hum from amp downstairs. 

Is there some kind of ground lift or something I can use on my computer or something? I’m open to trying anything at this point. It’s a 27” iMac. Never had such issues with my Mac Mini that preceded it. 

I’m thinking the actual Earth on the house, or at least the upstairs ring main needs looking at? 

It’s PISSING ME OFF!!! 

If I try to record guitar upstairs in the same room as the computer, if I position it just so, the hum largely disappears. 

Which is what I don’t understand. The hum is largely position dependent. 

I also noticed this downstairs. If I moved the guitar, the hum would get louder and quieter. Even though the computer is upstairs. 

No buzz at all when computer is off and no buzz when I set the computer up downstairs (and it’s turned on) right next to the amp/guitar in close proximity. 

I don’t understand this at all and it’s severely hacking me off!!!! 
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Comments

  • fretmeisterfretmeister Frets: 15511
    Always easy to problem solve when the kit isn't identified!
    Humans will swim in the sea even though there are many corpses in it.  They will not swim in a pool with a corpse in it. 
    Therefore all humans have a water / corpse ratio that is acceptable to them.
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  • NerineNerine Frets: 1244
    I’ll add, I have a positive input ventilator in the loft that’s always on. Could this be interfering with the Mac somehow, which is in turn interfering with the guitar? 

    Guitar doesn’t buzz upstairs if Mac is off. 

    Buzz only occurs on my guitar anywhere in the house if the Mac is turned on and it’s located upstairs. No buzz if Mac is downstairs. 

    I’ve disconnected everything from the Mac so it’s literally just a power cord connected to it. I’ve tried three different power cords. 

    Perhaps the next experiment is to move guitar upstairs and turn Mac on downstairs to see if it causes amp/guitar to buzz upstairs?? 
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  • NerineNerine Frets: 1244
    edited July 26
    Always easy to problem solve when the kit isn't identified!
    It’s a Friedman Small Box and a Suhr Alt T. 

    I’ve already mentioned the Mac. 

    It’s not just this amp and guitar. My Marshall is the same and when I borrowed my friends Quad Cortex the other day, it was the same. 

    Hum goes away if guitar is turned down or is unplugged from amp. 

    So something is interfering with the guitar, I suspect. 

    All three of my guitars need to be in the same physical position in the upstairs room if I am trying to record something to minimise the buzz. 

    But downstairs, the Mac does not make the guitar and amp buzz. 
    If the guitar and amp are downstairs, and the Mac is turned on upstairs, voila! Buzzzzzzzzz. 
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  • fretmeisterfretmeister Frets: 15511
    Genuine single coils in the guitar?
    Humans will swim in the sea even though there are many corpses in it.  They will not swim in a pool with a corpse in it. 
    Therefore all humans have a water / corpse ratio that is acceptable to them.
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  • NerineNerine Frets: 1244
    Genuine single coils in the guitar?
    Humbuckers. 

    In the coil split positions it is worse, though. 

    Les Paul buzzes and so does my other Suhr which has two singles and a humbucker. 

    I seem to remember the hum cancelling positions in position 2/4 on my Classic Pro being the best of the bunch. 

    But again, all of this only applies if the Mac is on. Rig is silent otherwise. 

    If the Mac is downstairs next to the amp and guitar, there isn’t a problem. 
    I tried this as I thought with it being quite a large display that the screen might have something to do with it. But it seems to be dependent on where things are plugged in in the house as to whether it happens or not. 
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  • fretmeisterfretmeister Frets: 15511
    Something the Mac power supply I bet. Can you move it or the amp onto another part of the house circuit. Run an extension cable and plug the amp in the kitchen for example. Just to have a look.

    I have trouble in my house when my tumble dryer is on.
    Humans will swim in the sea even though there are many corpses in it.  They will not swim in a pool with a corpse in it. 
    Therefore all humans have a water / corpse ratio that is acceptable to them.
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  • NerineNerine Frets: 1244
    I also did not have this problem with my last Mac. It has a two prong power input. Kind of like what you see on the back of a PlayStation. 

    This iMac has a normal kettle lead style, three prong input. 

    As most RF buzz (I think) is usually down to proximity, I was pretty alarmed when I turned on my computer upstairs and literally heard my amp go haywire downstairs. 
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  • Jimbro66Jimbro66 Frets: 2082
    edited July 26
    Is the positive pressure vent fan on the same upstairs ring main as your Mac or does it have its own dedicated supply from the board? Is the Mac positioned not far from the vent?
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  • NerineNerine Frets: 1244
    Something the Mac power supply I bet. Can you move it or the amp onto another part of the house circuit. Run an extension cable and plug the amp in the kitchen for example. Just to have a look.

    I have trouble in my house when my tumble dryer is on.
    I’m going to try switching the location of everything this evening. 

    I’ll try the Mac downstairs and see if the amp buzzes when it is upstairs. 

    I am leaning towards the Mac being the issue. Problem is, I’m not sure what I can do to combat it. I’m going to try running an extension from downstairs to upstairs and have everything set up upstairs as normal (with the exception of the Mac power being supplied from downstairs. 

    It’s such a headf*ck.  :( 
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  • HottubesHottubes Frets: 291
    edited July 26
    The positive pressure fan should be on the upstairs lighting cct, if it's a house or downstairs in a bungalow. normally !!. That's a weird scenario. Try pulling the fuse, at fused spur for the fan if you want to isolate that.

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  • ICBMICBM Frets: 56948
    The most likely explanation I can think of is that the upstairs mains wiring isn't properly earthed. Running an extension cable up there from downstairs with the computer still physically upstairs will confirm that (or not).

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • NerineNerine Frets: 1244
    ICBM said:
    The most likely explanation I can think of is that the upstairs mains wiring isn't properly earthed. Running an extension cable up there from downstairs with the computer still physically upstairs will confirm that (or not).
    I’m beginning to think the same. 

    Since my earlier post I have tried turning off all the extraneous trips in the house. 

    So, upstairs and downstairs lighting etc. Just left sockets on. No change. 

    What I found strange however, was that in an earlier post, I mentioned that the positioning of the guitar had an effect on how bad the hum was. 

    The exact same orientation downstairs as upstairs yielded the least amount of buzz. 

    So for example if I orientated the guitar to the East, say, and point the headstock down slightly, the buzz clears up. Same as in the upstairs room. 
    If I point the guitar face up towards the ceiling, the buzz is awful in both rooms. 

    I didn’t think Earth/ground buzz could be variable with guitar orientation? I thought it would be a constant? 

    Also, holding the strings doesn’t help. The buzz is there regardless. 

    This really sucks. 
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  • ICBMICBM Frets: 56948
    It's not "ground buzz" - there's no such thing despite popular convention naming any hum or buzz that...

    *Ground hum* is a specific type of hum (and it always is *hum*, not buzz), which is caused by a ground loop between two pieces of equipment. And you're correct, it is constant regardless of guitar orientation because it's not picked up by the pickups.

    What you have sounds like the radiated electromagnetic noise from a switch-mode power supply. It is directional, so the orientation of the guitar pickups relative to the source matters.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • NerineNerine Frets: 1244
    ICBM said:
    It's not "ground buzz" - there's no such thing despite popular convention naming any hum or buzz that...

    *Ground hum* is a specific type of hum (and it always is *hum*, not buzz), which is caused by a ground loop between two pieces of equipment. And you're correct, it is constant regardless of guitar orientation because it's not picked up by the pickups.

    What you have sounds like the radiated electromagnetic noise from a switch-mode power supply. It is directional, so the orientation of the guitar pickups relative to the source matters.
    Thanks, ICBM. Is there any piece of equipment that may be able to remedy this? I.e. AC Mains related or gear related? i did think of a ground lift, a humdinger type thing, a power conditioner etc.  

    I have gleaned some more info.

    I have tried another three sockets. 

    Here is the setup: Amp plugged in, turned on, guitar connected with one cable, guitar volume up. Guitar on a stand. This is upstairs.

    If I attach the Mac power cable to a socket in the same room as the amp power socket, I get some short pulses of buzz through the amp. This is without the Mac being powered on. The pulses last approx 0.25s I would think. They seem random. 

    When powering on the Mac (every other piece of studio gear unplugged) the buzz is hideous. 

    Tried on the same 4 gang as the amp. Same result. Hideous buzz.  

    If I run an extension from downstairs and power the Mac like that, there is no buzz, and the noise that is already being produced by the amp does not change. 
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  • ICBMICBM Frets: 56948
    Nerine said:

    Thanks, ICBM. Is there any piece of equipment that may be able to remedy this? I.e. AC Mains related or gear related? i did think of a ground lift, a humdinger type thing, a power conditioner etc.  

    I have gleaned some more info.

    I have tried another three sockets. 

    Here is the setup: Amp plugged in, turned on, guitar connected with one cable, guitar volume up. Guitar on a stand. This is upstairs.

    If I attach the Mac power cable to a socket in the same room as the amp power socket, I get some short pulses of buzz through the amp. This is without the Mac being powered on. The pulses last approx 0.25s I would think. They seem random. 

    When powering on the Mac (every other piece of studio gear unplugged) the buzz is hideous. 

    Tried on the same 4 gang as the amp. Same result. Hideous buzz.  

    If I run an extension from downstairs and power the Mac like that, there is no buzz, and the noise that is already being produced by the amp does not change. 
    That must be an earth fault with the upstairs wiring if you're not changing anything other than powering the Mac from downstairs. You need an electrician.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • NerineNerine Frets: 1244
    ICBM said:
    Nerine said:

    Thanks, ICBM. Is there any piece of equipment that may be able to remedy this? I.e. AC Mains related or gear related? i did think of a ground lift, a humdinger type thing, a power conditioner etc.  

    I have gleaned some more info.

    I have tried another three sockets. 

    Here is the setup: Amp plugged in, turned on, guitar connected with one cable, guitar volume up. Guitar on a stand. This is upstairs.

    If I attach the Mac power cable to a socket in the same room as the amp power socket, I get some short pulses of buzz through the amp. This is without the Mac being powered on. The pulses last approx 0.25s I would think. They seem random. 

    When powering on the Mac (every other piece of studio gear unplugged) the buzz is hideous. 

    Tried on the same 4 gang as the amp. Same result. Hideous buzz.  

    If I run an extension from downstairs and power the Mac like that, there is no buzz, and the noise that is already being produced by the amp does not change. 
    That must be an earth fault with the upstairs wiring if you're not changing anything other than powering the Mac from downstairs. You need an electrician.
    Yep, that was as I feared tbh.

    It's a Victorian house and the wiring must be a complete hotchpotch. 

    I'll call an electrician today. 
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  • ICBMICBM Frets: 56948
    edited July 27
    Nerine said:

    Yep, that was as I feared tbh.

    It's a Victorian house and the wiring must be a complete hotchpotch. 

    I'll call an electrician today. 
    It's not the Victorians you have to worry about, it's the modern bodgers...

    My parents had a Victorian house. One day my mum complained that she thought she got a slight electrical tingle from the washing machine, so my dad went to investigate. Sure enough, it was apparently live. He traced it back to the distribution box and found an earth wire was hanging just below the terminal block. Thinking it hadn't been secured properly and had popped out, he undid the terminal screw and poked it back in.

    There was a large blue flash and everything in the house went out.

    The ring main earth had been disconnected because it - and everything plugged into it, including the (luckily white-painted) washing machine casing - was live. After a huge amount of work to isolate exactly where the fault was by disconnecting the incoming and outgoing cables in each power socket in the whole downstairs of the house, we found the cause... a nail had been driven through a cable and bridged the live and earth. The "electrician" who discovered that it couldn't be powered up without blowing the fuse (pre-RCD) had "fixed" the problem by disconnecting the earth.

    Done in the 1980s, not the 1880s ;).

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • HottubesHottubes Frets: 291
    edited July 27
    Turn the power off completly and unscrew the sockets upstairs and tighten all the earth terminals as well as the lives and neutrals.

    Due to the age they're probably loose anyway. AC does this over years, as it cycles up 180 back to 0 the - 180. Unlike DC which is smooth man.


    Edited Disclaimer if you aren't comfortable doing this don't.
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  • inewhaminewham Frets: 13
    Better still get a sparky in to Megger it rather than electrocuting yourself.
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  • HottubesHottubes Frets: 291
     This,Totally agree.
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