Things I've learnt about... grounded vs. non-grounded, etc.

Discussion in 'General DJ Forum' started by djkee, Nov 1, 2005.

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  1. djkee

    djkee NI Product Owner

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    A lot of people seem to be very reluctant to use their laptop ungrounded (by use of 2-to-3 prong adapter or removal of ground pin on power supply - basically disconnecting, removing or "lifting" a connection to ground somewhere in your system). The reasoning behind this reluctance to do this seems to be that you are exposing yourself to power surges and damaging your equipment.

    Although there is some degree of truth to this, it has really been elevated almost to the point of urban myth...

    Yes it is possible to fry your electronic equipment if it is not properly grounded, BUT it is very, very unlikely. Those people who tell you not to ever do this are usually in my experience either: paranoid alarmists, IT & computer engineers or studio audio/video guys. I'm not going to say that they are wrong... just that they are a bit overzealous. Having worked in some related fields, I know that what I was taught in the lab, server room or studio and what I experience in real world out in the field are very, very different.

    Honestly, in our business (as DJs) you have much higher chances of a drink getting spilled or even thrown on your laptop than having it taken out by a power surge. Even if you have a "no drinks" policy in your DJ booth, you know what kind of crap happens at a good party... LOL.

    As a professional live-sound engineer by day, I can tell you that in my industry, an AC ground lift is a standard piece of equipment in my tech-kit. We don't use it a lot because most of the time we have professional electricians dropping power for us to suit our exact needs, but when you are at a different venue every day there is always some place with crappy power or ground, etc.

    Only once in my 8 years as an audio technician for large concerts, conventions and other events, have I seen equipment get burned out due to a power problem... that was because the electrician wired it wrong (2 hot lines instead of 1 hot and 1 neutral). Every other time that there was some type of power issue, the equipment may have acted up, but the only piece of equipment that was blown (if at all) was the surge protector - after the power issue was fixed and equipment restarted, everything worked fine.

    YES, it is true - ideally speaking you should have proper power and ground. But as a DJ, it is not my responsibility to troubleshoot power and ground in some nightclub that is only paying me only so much for just a few hours work. If I was setting up my own nightclub or studio that would be different, but if you are doing live stuff in who knows how many different venues every day of the week, you just gotta be prepared to deal with it and that little adapter can save your life.

    Why this is reasonably safe:
    Most decent laptop power supplies will automatically adjust for fluctuations in frequency and voltage (most desktop computer power supplies do this as well). In the US, 120volts 60 Hz is the standard for AC power, but my Dell laptop power supply will handle roughly from 50-60Hz and 100-240volts. This means for most AC power surges or brownouts you will still be covered provided you use a good-quality surge protector (or as someone else suggested a UPS). This is why many laptops (even high-end ones such as Sony or Apple) don't even come with a 3-prong power cord - it isn't really very necessary.

    In my opinion, the only reason that certain laptopos, most notably Dell, Compaq/HP and Thinkpads, have a 3-prong power supply in the first place is because they are going after the corporate market and some large corporations or government agancies have restrictive guidelines for what kind of electrical equipment they can buy (for liability purposes they can only get grounded electrical equipment).

    The laptop power supply should cover for most AC power problems - what about direct current(DC) spikes coming over the AC lines? A good surge protector should cover for large DC voltage spikes and surges. If something does happen, it may blow the surge protector/UPS or even the laptop power supply, but chances are your laptop will be OK. Chances are that if your laptop gets fried, it was something truly unforseen like a lightning strike on your building or right outside the building and even if you had your equipment grounded it still would have ended up being fried.

    In terms of the kinds of noise and hum I have seen when using Traktor and Final Scratch, there are TWO potential sources of noise and hum that can get into your system via a grounded laptop power supply.

    The first is a pretty standard audio hum that is caused by one of the other componenets in the audio signal chain and a mismatched ground - it could be mixers, amps, or even lighting and lighting controllers hooked up on the same circuit. Anyone who has played on turntables knows the sound of a turntable ground wire that is loose or disconnected. There are other variations of audio hum and noise, but they are usually characterized buy a constant background noise that is limted to a pretty narrow pitch or frequency range.

    Yes it is true, this kind of noise can often be fixed by placing a ground hum eliminator or isolator ("Iso") at the correct place in the audio signalchain. (Not always - I've had times where I had to use an ISO, but also had to lift the ground on the power for a certain piece of equipment). I carry both with me because sound and audio are a part of both my day and night jobs.

    However when dealing with laptops, that is not the only type of noise...

    The second type of noise is something I saw for the first time with my laptop when i used Final Scratfch 1.5. It is a noise caused by computer equipment (especially hard drives and CD drives) that gets into the output from your sound card (internal laptop and/or external usb/firewire, etc.). The sound of this type of noise is different than the usuall audio humm or rizz. It is a digital sounding noise that is not a constant tone and may get louder or softer as your computer sends data to/from drives our soundcards.

    Some laptops, drives and soundcards are more prone to this noise than others, but usually it is most noticeable when using an external device over Firewire, USB, etc.

    The only fix that I know of for this digital type of noise involves disconnecting or "lifting" a grounding cable or connection somewhere in your system. My quickest fix is lifting the ground on the laptop power supply - that should kill it. The other possible fix is to cover the outer metal jacket of any usb firewire connectors with a small piece of electrical tape. I prefer the ground lift because I don't want to risk damaging the USB or firewire jacks and plugs with tape residue or by jamming a larger tape-covered plug into the jack. The only other fix for this would be very expensive and time consuming - buying different soundcards, computers and hard drives until you find a combination with little or no noise.

    To summarize...
    This is my advice if you are really worried about lifting the ground from your laptop power supply because you are afraid of frying your system from a power spike or other power-problems: (a lot of this is common sense, but I'm including it anyways)

    First - invest in a good surge protector, power conditioner and/or UPS. I have a $50 surge protector from Monster Cable that even has an audible alarm on it. It came with a lifetime warranty and I already had it replaced once because of an incorrectly wired socket - the alarm went off as soon as I plugged it in and before I had even turned on the master switch to power my sound system on. It did it's job and saved my system.

    Second - you should learn to differentiate between audio hum/noise and digital noise. For audio hum/noise, get an ISO or Hum Eliminator. For digital noise use a ground lift or put tape on the connectors of the problem USB or Firewire device.

    Third - if you are still worried, start saving up for a backup computer and other backup equipment. For example, because both my day and night jobs depend on computers, I have 1 computer for DJing and another one for my audio work, but I have duplicate software on both so I can also use each one as a backup in case the other dies. I also keep my "Traktor" folder on my external hard drive with my music collection so that whichever computer I am using I will always have all my playlists, etc. ready for me to use. The external hard drive I take on gigs is not my only copy - I have another bigger hard drive i keep at home with all my music and other vital files on it. This way if one of the drives gets corrupted, you have another copy of everything.

    Fourth - if you intend on really getting serious about DJing, music production or related fields as a career or sideline, learn your craft. Read some books or take some classes or seminars on audio basics, electricity/wiring, computers, etc.
     
    Last edited: Nov 1, 2005
  2. Hi-T

    Hi-T NI Product Owner

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    Nice post! Plus +1 all the way.
     
  3. stompinne

    stompinne NI Product Owner

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    I had my laptop connected with a M-audio firewire soundcard, and guess what....terrible noise when playing on power cord (none with laptop-battery).

    I placed this piece between the set and the amp, no noise at all, everything's fine:

    http://www.skytronic.co.uk/product/product.php?s=201.171
    Someone said to me it's been used in car-hifi, for hum-problems.

    But can those humdestroyers be trusted? Can i damage some materials (amp,..)??
     
  4. boysteve

    boysteve Forum Member

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    I use one of these in my car to eliminate ground loop hum. I have 2 Infinity Kappa Perfect 12.1 subs connected to a 2000-watt 2-channel sub amp crossed over from another 4-channel amp for the post/door speakers (is this funny or what--my PA isn't this powerful), and picked up ground loop (arrrgh!) that drove me nuts. This works pretty dang well--$16.00 from Radio Shack. (it's male to male, though, so if you get one of these, you'll want RCA adapters to plug into a house mixer). And no, it won't cause any damage; it's passive and doesn't actually DO anything to the voltage.

    I picked up two of them, cuz I figure since it's got RCA connectors for unbalanced connections, it ought to work next time I pick up 60Hz hum going through a house system. It's happened to me before, and can happen not just because of your laptop/pc, but because an unbalanced connection has been entered into the audio chain.

    Ebtech makes a gizmo called a Hum-X that looks like a two-prong adapter. It contains circuitry that isolates ground hum and seems like an ideal solution if the laptop is the source of the problem. Only catch is, the Hum-X is about $75.00
     
  5. DJMarkSF

    DJMarkSF Forum Member

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    This whole issue was one of the major reasons I changed from a Windows XP-based laptop to a Powerbook. With the Powerbook's Firewire, you don't need to use the power cord for the audio interface, effectively eliminating the ground loop at the source.

    If I had been able to find a Windows laptop that had a powered 6-pin firewire port, that (and the presently higher CPU horsepower of the Centrino laptops) would have probably been enough to keep me using Windows for this purpose.

    I've also used those Radio Shack "Ground Loop Isolator" transformers with good results before, but I think it's worth noting that they're *not* penalty-free in terms of the audio performance. How much (or how little) degradation you get is dependent on the levels you're running through them, and to a lesser extent the input/output impedences of the gear they're connected in between. Jensen and Rane make similar units with much higher quality, although with higher pricetags as well.
     
  6. stompinne

    stompinne NI Product Owner

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  7. DJMarkSF

    DJMarkSF Forum Member

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    They're audio transformers, and the kinds of degradations they can produce includes rolloffs at the frequency extremes, increased distortion (most commonly at lower frequencies), and overshoots/ringing on transients and square waves. Better-quality transformers will minimize these effects.

    You might find it useful to do a level-matched "A/B" test using a waveform editor.
     
  8. boysteve

    boysteve Forum Member

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    It's true they add a level of impedence to the signal, and I've never tested one of these out on a huge system. It might make a difference.
     
  9. djkee

    djkee NI Product Owner

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    Yeah, I wouldn't personally wouldn't use one of those radio shack or car-audio hum reducers (they look like a C-batttery, but heat-shrinked with RCA cables coming out both ends) - Coloring your sound more is not the goal of killing noise.

    I just use a ground lift on the AC power - that was the point of my original post... that it's for the most part OK to use one. Like I said, as a DJ you have higher chances of a drink spilled on your laptop than a large enough surge to kill your computer. That kind of surge is could happen but it is very unlikely.

    As an audio guy, the only type of device I would put into my audio signal chain for hum is an isolation transformer or a DI with ground lift.
     
  10. Dijibuddha Magnetik

    Dijibuddha Magnetik NI Product Owner

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    My understanding on the grounded laptop is more safety than equipment protection.Most,if not all laptops that I am aware of run off of a relatively low voltage low amperage DC power which is converted from a high voltage AC current via the laptop power supply.
    So far as I am aware the ground plug in this case is more to protect you in case someone spills eg:"beer" on the power supply so the "benevolent" current runs safely through the ground plug instead of whomever might be grabbing the guy who grabs the power supply to drain the beer out of it!
    It seems to me that the most likely piece of equipment to get trashed in a brown out or other power failure would be the power supply,not the laptop itself.
    I'm not sure the laptop itself would have enough of a fatal voltage inside of it to kill you in an ungrounded beer spill,unless maybe the capacitors are a factor?
    Please feel free to prove me wrong.This is just my understanding of the matter.
    I have long since removed the ground plug from my laptop power supply and henceforth have carefully avoided the spilling of beer on my gear.
     
  11. djkee

    djkee NI Product Owner

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    149
    That is sound in principle, but in reality, most laptops only use 50-100 watts, which translates to less than 1 amp at 120 Volts (less than 1/2A at 220v).

    To quote my old science teacher - it's the amps, not the volts that can kill you... but a laptop does not have nearly enough amperage to kill or seriously hurt you.

    Even if you stick a paper clip in an electrical outlet (BTW, I don't recommend this) - it would cause physical pain and possibly muscle spasms, but I doubt it could even cause you to lose consciousness unless you could were exposed to that kind of current for long periods of time. Most people's reflexes would cause them to jerk away from the source of electricity immediately. The temporary pain caused by a momentary shock from a normal wall outlet would not linger more than a few minutes.

    Most 120V (North America) outlets are breakered (or controlled with fuses) at between 15-30 amps, and if you have a surge protector/power conditioner/UPS on your gear (like you should) that is two levels of protection (surge protector and the breaker/fuse-box). And your laptop power cable might have a fuse inside it (my dell does), so that makes 3 layers or protection.

    The static electricity that can build up inside a CRT monitor picture tube could potentially kill you, but with how modern tubes are designed it is pretty unlikely to get shocked during normal use. You would almost have to be taking apart or taking a bath with it to expose yourself to that kind of lethal voltage.
     
  12. nickrb

    nickrb New Member

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    Im a bit confused. How do it lift the ground on my laptop? Is it just a case of removing the earth wite from the 3 pronged plug at the end of the power supply?
     
  13. duckilo

    duckilo NI Product Owner

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    I'm not sure why, but many times I've seen people plug Windows based laptops into sound systems there's a terrible ground hum, especially when the AC adapter is plugged into the laptop.

    However, this never happens when an Apple Mac is used in the same manner (with the AC outlet plugged into the back) even when the audio is piped out from the headphone socket and not Firewire. Not sure why exactly but Macs seem to not have this problem.
     
  14. boysteve

    boysteve Forum Member

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    This month's Electronic Musician (normally I magazine I don't like, but it was free at the Remix Hotel, so wtf) has an extensive article on plugging in and electrical paths. Very informative. Lots of ground-loop myth debunking, too.
     
  15. DJ Freshfluke

    DJ Freshfluke Traktor Mod Moderator

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  16. sionm2000_Tf

    sionm2000_Tf New Member

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    Right, sorry to sound thick but just wondered if anyone could give me some advice. Established that the hum coming from my setup is caused by my external hard drive so therefore must be digital noise. So just wondering if someone could recommend a ground lift and where and how do i connect it to my setup?
    Cheers
     
  17. djwampus

    djwampus Forum Member

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    i am having the hum problems. when i disconnect my power adapter it goes away. so do i need the hum-x or Behringer HD400 2-Channel Hum Destroyer??????? the prices are very different! thanks for the input.
     
  18. boysteve

    boysteve Forum Member

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    I'd go for the Hum-X. Connect gear to power strip, power strip to Hum-X, Hum-X to outlet. I don't trust anything made by Behringer.
     
  19. djwampus

    djwampus Forum Member

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    thanks for da info.
     
  20. DjTwIcE

    DjTwIcE New Member

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    Here's my 2 cents

    One of the very first things I learned over 18 years ago when I sarted was that ground lifters where an essential tool to have in your kit! lol

    Most set up's "bar's&clubs" are close to neon's fridges and god only knows that Fred "the club's handy man" sure knows how to run electrical!

    With what I use right now, 1 good quality surge protection power bar, ground lifter plug on my laptop and it stopped the noise my hardware made and I've never ran into any glitches.

    Do I recommend it...not sure since I'm no expert but it works for me. I travel between 3-5 different bars/clubs around where I am and everyone except for one of them as electrical that would make your fire marshall freak.
     
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