Hiss and Hum

Discussion in 'Technical Side of Things' started by epimetheus81, Oct 20, 2021.

  1. epimetheus81

    epimetheus81 Electromatic

    48
    Mar 2, 2009
    Berlin, Germany
    Hey folks.

    I've been testing my new AC10 with my G5422 and am having some problems with hiss and hum coming through. Its amplified when I use my delay because, well...it echos. There's some hum with my SG, but much less, even with higher gain, so my guess is dirty power and interference with the Blacktops?

    I had a similar problem with my VT20x that I recently sold, only it was louder(!). Again, mostly muted with the SG. If I plug in the Katana, there's not much of anything.

    From searching around the forums, my guess is an issue with the power in the room. There's a dimmer switch, florescent bulbs, and my PC setup, which I use for recording. Any strategies for troubleshooting and eliminating the noise? Are there ways of filtering the power?
     
    Last edited: Oct 20, 2021
  2. stevo

    stevo Friend of Fred

    May 1, 2012
    Atlanta
    White noise isn't something I usually associate with dirty power. Power comes as hum from 60 cycles, ticking from switching power supplies for pedals etc. A dimmer usually has a funky noise that isn't white noise. Fluorescent bulbs cause hum. And hum, while it comes from your power, isn't necessarily an indication of dirty power. It's more of an indication of poor AC rejection by the amp.

    White noise usually comes from amplification such as noisy opamps in pedals or from your amp itself.
     
  3. oneforsorrow

    oneforsorrow Synchromatic

    784
    May 15, 2020
    Iowa
    I had a delay pedal that was notoriously noisy. It was cheap pedal and I moved on but I did notice a marked improvement in my other pedals when I went to an isolated power supply. I would trouble shoot the issue by listening to the amp powered on but with nothing plugged into it. Then add the guitar. Then add the pedal(s). Perhaps do the same thing in different rooms where the outlets are on different circuits and see if anything reveals itself.
     
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  4. wabash slim

    wabash slim I Bleed Orange

    Age:
    72
    Feb 10, 2010
    lafayette in
    All of those could be sources for noise. Simple troubleshooting procedures would be to turn everything off, and turn one thing on at a time till you find the cause. It could be your AC power as well. Even turning your gear 90 degrees could help. Also, never run AC cables alongside of signal wires. Do the same with your guitar and amp setup. Start with plugging straight into the amp, then try it with one pedal at a time.
     
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  5. epimetheus81

    epimetheus81 Electromatic

    48
    Mar 2, 2009
    Berlin, Germany
    Thanks for the replies so far. I edited my initial post since "white noise" isn't an accurate description of what's going on. There's some 60 cycle hum, but also some light fluffy static coming out. Rather than try to describe it poorly, here's a clip:

    https://www.dropbox.com/s/bkz0yxjp1e9s8kx/amp hiss.m4a?dl=0
     
  6. stevo

    stevo Friend of Fred

    May 1, 2012
    Atlanta
    Sounds like you have a grounding issue. Hard to evaluate the hiss for the ground hum.
     
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  7. wabash slim

    wabash slim I Bleed Orange

    Age:
    72
    Feb 10, 2010
    lafayette in
    Static could also be a dirty connection due to a cable connector or jack.
     
  8. Gretschtim1

    Gretschtim1 Country Gent

    Dec 4, 2012
    Dundalk, Md
    Is the sound on the recording you posted with everything plugged into the amp (pedals, guitar, etc.)?
    It sounds like the amp is doing it's job and amplifying what's plugged into it.
    Like Wabash said - start with just the amp idling nothing plugged in. Then add the guitar and then one pedal at a time. To me it's a few noises. Cheap wall wart power supplies for your pedals can add lots of noise. It seems I'm hearing some of that. What pedals are you using?
    Is the amp quiet without anything plugged into it?
    If it turns out to be a pedal try powering it with a battery and see if it quiets down. If it does the power supply is your problem. Cheap patch cords could add to your noise as well.
    One last thing Vox amps have a bit more high frequencies than most other amps which will boost that hiss type sound you are hearing.
    The low hum which sounds like an octave above 60HZ could be a bad foot pedal power supply as well. If you are using the same power supply to power a few pedals that could compound the noise problem. There's no filtering on cheap supplies.
     
    Last edited: Oct 20, 2021
  9. epimetheus81

    epimetheus81 Electromatic

    48
    Mar 2, 2009
    Berlin, Germany
    Thanks for the replies so far. Been running around and can't remember if that was just amp or guitar into the amp. What I do remember is that the sound of the guitar into the amp and the amp alone were the same when I tried earlier.

    I plugged in the amp in another room (no dimmer on the main light) and got the same sort of noise.
     
    Last edited: Oct 20, 2021
  10. oneforsorrow

    oneforsorrow Synchromatic

    784
    May 15, 2020
    Iowa
    Not knowing what items may be available to you in Germany but I've been saved by my Hum X multiple times.
     
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  11. epimetheus81

    epimetheus81 Electromatic

    48
    Mar 2, 2009
    Berlin, Germany
    Started fresh this morning and the clip matches both the sound I get with just amp straight into the wall and with a guitar plugged in. there's not much change. When unplugged, I get a little pop when I touch the input, which leads me to think you all are right about grounding. On my next break, I'll give the jacks and plugs a light cleaning and try again.
     
  12. Londoner

    Londoner Gretschie

    274
    Dec 18, 2020
    UK
    Doesn't Germany run on 50Hz AC?
     
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  13. Roy Clark

    Roy Clark Synchromatic

    675
    Jun 16, 2017
    Bat cave.
    [​IMG]
     
  14. NowEarThis

    NowEarThis Gretschie

    Age:
    70
    231
    Jun 23, 2021
    Northern Rivers NSW Australia
    If you're still getting the same noise with nothing plugged in then it's the amp.
     
  15. epimetheus81

    epimetheus81 Electromatic

    48
    Mar 2, 2009
    Berlin, Germany
    That's what I figured. Hoping nothing came loose when I opened it Monday to see if the tubes were as described. Didn't really even remove the back from the cab since I didn't want to mess with the speaker cable. I remember there being noise before (in another post), so my guess is it arrived that way.

    Hoping I don't have to go back in to diagnose it.

    Yup, looks like it does.
     
  16. Perhaps not the amp:

    Probably been said:
    Are all the outlets actually 3 wire grounded?

    In the US anyway, older housing may have wall plates which appear to be grounded, but may not truly be.
     
    Last edited: Oct 21, 2021
    wabash slim likes this.
  17. NowEarThis

    NowEarThis Gretschie

    Age:
    70
    231
    Jun 23, 2021
    Northern Rivers NSW Australia
    Try these steps to diagnose:

    Unplug the input lead and turn all the knobs down to zero. Has it gone away?
    Yes: Begin turning up knobs until the noise returns.

    If it has reverb, was it the Reverb knob? Yes: Check your wiring connections to/from the reverb pan to the amp, and also the reverb pan itself will pick up noise if it's near power cables or electrical devices.

    Was it a volume/tone knob? Yes: Most likely a dud pre-amp tube.
     
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  18. Gretschtim1

    Gretschtim1 Country Gent

    Dec 4, 2012
    Dundalk, Md
    Okay that narrows it down to a faulty ground in the power source or a problem in the amp. If the noise is there using a different amp then it's the power source. If the noise goes away using a different amp then your new amp has a problem and needs to be returned or looked at by a technician.
     
    Runamok likes this.
  19. Scamp

    Scamp Gretschie

    241
    Feb 22, 2018
    SoCal
    If you can take your gear over to a friends, preferably in a different area, and plug in and see if you still have the noise. If no noise its most likely on your house line most lf you still have the noise it's probably your gear.
    Sometimes the noise on you house lines can come into your house and can be the result of what a neighbor may have on the line. We had Edison come out to hour house because of a noise and they checked the outside lines and traced it down to my next-door neighbor's house. They had an aquarium and the pump/filter was making the noise. The Edison guy said that they find that a lot with aquariums. One way we used to check lines in the house way back was to plug in an old AM radio. They pick up most anything on the line
    One of the biggest cause of noise on equipment is poor ground either on the plug/line or your gear. When I had to replace the house electrical panel all my noise on lines went away and I had a lot better ground on my plugs too. Of course I had to replace it because it was so old, 1963, and the breakers weren't working properly not just to eliminate the noise only amp LOL
     
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  20. section2

    section2 Country Gent

    Dec 21, 2016
    Toronto
    As others have said, it sounds like there's an issue with the amp and/or the power source.

    But you also mentioned that the noise is much worse with your 5422 than with your SG, so I suspect that your 5422 might be picking up some interference and adding it to the mix. If you're sure that everything in the guitar is properly grounded, your wiring harness might not be adequately shielded.

    For what it's worth, I get a lot of hiss from my 5620 when it's plugged into my Zoom G5 pedal, but I get no hiss from my PRS SE 245 through the same rig. I think it comes down to the limited shielding in these guitars.

    As an experiment, I took a spare set of Blacktops in their stock factory wiring harness (not connected to a guitar) and plugged them into the G5. Lots of hiss. Then I wrapped the harness in aluminum foil. No hiss.

    They obviously can't shield the cavities in a hollow or semi-hollow guitar—the whole thing is a cavity, and there are big holes in the top!—so it comes down to the wiring.

    I don't know what kind of shielding (if any) is used on the stock wiring harness, but I'd imagine that the hiss could be eliminated by replacing the harness with a good set of shielded wires, or at least wrapping the wires in grounded braided sleeves. That might darken the tone, but it could address the hiss.

    That's more work than I wanted to do, though, so I just put a noise gate at the beginning of my signal chain. Problem solved.
     
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