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dirty power

Discussion in 'Recording' started by Krou, Oct 13, 2004.

  1. Krou

    Krou Active Member

    May 27, 2001
    No matter where I plug my speakers in (KRK V6 II), there's always a little "shhhhh+very low crackle" going on when I place my ears close to the tweeter. Not loud enough to get too much in the way of mixing when I'm sitting 4 feet back but still, I know it's there and when the music stops for a while, I somehow can hear it and it's starting to piss me off.

    I've read about plugging all gear to the same outlet/breaker, which is what I'm doing [they're plugged into a rackmounted Furman RP-8], I have no dimmer switches and all my audio and power cables are relatively well spaced and tidy (no angled crossings between them).

    Could it be that power in my building is just shady and there's not much that can be done on that end? Perhaps a different type of power strip could help? Some kind of power conditioning strip - anything you recommend for this type of situation?

    Thanks for any help.
  2. Kurt Foster

    Kurt Foster Distinguished Member

    Jul 2, 2002
    77 Sunset Lane.
    Are you in an apartment building or a single family residence ... commercial building? Many times noisey power comes from worn wall sockets and light switches or breakers. When the contacts get old they do not make solid contact and this causes arcing which generates hum and crackeling.

    If possible try replacing all the wall recepticles and switches ... have an electrician come in a replace the breakers in the main box. Ask the power company to check out the power to your studio. If possible, the best thing is to have an electrician provide a dedicated leg off the main 220 feed into the building for nothing but audio gear.

    If all that fails, you could try a balanced power transformer but I would turn to that as a last resort as those things are very expensive.
  3. tony desilva

    tony desilva Guest

    I agree with everything Kurt says. Here are a few steps you could use to identify the problem:

    Do you hear the hum/crackle even with the audio cables disconnected from the inputs of the speakers?

    If yes, then you either have a power problem or marginal components in the power amp of your speakers (although its hard to believe that both speakers have weak components). You could easily carry the speakers to a friend's place or another studio and try them there.

    If not, then the problem is coming from your mixer or whatever is hooked up to it. If you are using a mixer, try disconnecting all cables from your mixer (mute all channel faders) and hook just the main audio outs to the speakers and see if you still have the problem when you bring the master faders up on the mixer. Disconnecting all cables from the mixer will prevent any ground loops (the usual cause of a slight hum). Then start connecting the cables up one at a time to try and identify the culprit.
  4. AudioGaff

    AudioGaff Distinguished Member

    Feb 23, 2001
    Silicon Valley
    KRK has had some docemented problems with buzz and hum and other noise issues with their monitors for the last few months. Call them and see if your model is on their list.
  5. RandomGuest

    RandomGuest Guest

    Feb 10, 2001
    You will find some hash and garbage on pretty much all power lines, use of things like Furman poswer conditioners/surge protectors will only serve to further mangle the wave form from the local Edison.

    If you want truly clean power you will need a "UPS". Not the BS kind they sell at the computer store, but a real one [they come with and without battery backup, I usually specify the ones without battery backup when working in "first world" nations as the batteries in these things cost a bloody fortune]. A real "UPS" will take whatever is coming from the wall, convert it to DC, then convert that DC to a clean sine wave. Most are programmable so you can run their output as balanced power or the more traditional "Hot/Neutral/Ground" power souce. You will also have the capability to switch between 50 and 60Hz as the frequency of your power.

    While unless you're running AC motors it probably doesn't seem like a big deal to switch between 50 and 60Hz... but I have found that things like "Plexi" Marshalls and some AC-30's respond quite favorably when powered with balanced 240v at 50Hz.

    As Kurt mentioned, the other things that are the same power grid as you will affect you power greatly. Things like a printing plant blocks away can introduce all kinds of hash and crap on the power lines as can a neighbor's refrigerator. There is all kinds of air born crap floating around as well. For this there is little remedy short of encasing your room in a Faraday cage... but it is what it is.

  6. Krou

    Krou Active Member

    May 27, 2001
    Yes, I know. My first pair was suffering from their factory buzz and they sent me a new set. This is now just a question of power and not the speaker. Thanks for the headzup. If it turns out to be yet another speaker defect - albeit not as severe as the loud buzz - then I'l regrettably steer clear of KRK and buy a set of Dyn BM6A's.

    To answer Tony's question above. Yes, the hum is still there when no audio cables are connected, it's simply a matter of plugging in the speaker and turning on the power switch behind the cabinet. I'm also not using a mixer, I monitor straight out of a Digi002R, which has no influence on the noise when present in the signal path.

    I may take it to a neighbor's house tonight and see if the problem persists.

    Thank you all for the bits of advice, I'll look into a UPS unit per Fletcher's suggestion. Is there a particular brand/model you would recommend to narrow the options?
  7. HMNP

    HMNP Guest

    Yeah Fletcher, which pro UPS do you use or name a couple of brands so we can look into them. thanks alot!

  8. LittleDogAudio

    LittleDogAudio Active Member

    Sep 24, 2004
    Another thing it could be is an outside transformer going bad. We had an issue at my studio and found that the transformer feeding my building was fine but a transformer on the next pole (about 10' away) was about to blow.
    Believe it or not, there was a sympythetic crosstalk between the two. When the power company swapped out the bad trans., everything was good.

    Just a possibility.

  9. Big_D

    Big_D Well-Known Member

    Aug 21, 2004
    Quakertown PA
    A UPS always has a battery. UPS stands for Uninteruptable Power Supply, uninteruptable being the key word here. The power is not interupted because the battery kicks in to provide power when the A/C fails. If it doesn't have a battery it is merely a power conditioner or power converter. The difference between computer store UPS's and network grade UPS's is the VA rating and runtime however they both provide clean power. Computer store UPS's generally don't exceed 1.5 kVA and have much smaller batteries so the runtime is short compared to network UPS's.

    I use a 2.0 kVA Network Grade UPS and it powers my DAW, Monitors, Mackie 1604, (2) Layla 24's, compressor and MFX processor. Mine is over 6 years old and is no longer produced but it cost around $1000 new. It weighs around 100lbs. You can expect to replace the batteries every 3 years or so, mine are $150. I never run amps or any other gear besides what I listed on the UPS. If you want to run more gear I would suggest a larger UPS. You can figure out how large of a UPS you need by adding up the VA requirements of all of the gear you intend to put on it. You can get good UPS units from APC, Tripplite Toshiba and Best. I listed approximate costs for various VA ratings below.

    1.5 kVA $600 to $800
    3.0 kVA $1100 to $1400
    5.0 kVA $2500 to $2900 (120, 240 and 208 V)
    10.0 kVA $4500 and up (208 and 240)

    Deltec and others sell units that are hard wired into your main panel and at 10 kVA can power an entire studio with ease.

    Hope this helps :D
  10. Big_D

    Big_D Well-Known Member

    Aug 21, 2004
    Quakertown PA
    I should also add that you should never put anything with an A/C motor or a laser printer on the UPS or on the same circuit as the UPS. The reason for this is A/C motors draw alot of current on startup. The UPS will attempt to make up for this by switching to battery power momentarily. If you have a freezer cycling on and off every 15 minutes these little draws on the battery take it's toll and shorten the battery life considerably. With laser printers it's the fuser that cycles on and off and causes the same condition. The bus on your main panel can give these items enough current to prevent this.

    Fletcher, thanks for the tip on the Plexi's and AC30's, I have an old Best 240 unit that isn't being used and would work well for this.

    It's funny you mentioned a Faraday cage. about 20 years ago a friend was using his basement as project studio and was constantly getting radio interference in his recordings (he had a broadcast tower a few hundred yards from his home). Our solution was to turn his basement into a giant Faraday cage by stapleing rolls of aluminium screen to the outside of the studs and joists and overlapping the screen slightly to maintain the sheild. While it was not elegant it worked and has had a second benefit, cell phones don't work in the studio. A member of a local band was stumped as to why his phone suddenly lost signal as soon as he set foot in the studio. We left him guessing.
  11. Sanity Inn

    Sanity Inn Guest

    Interesting reading,,,

    here i was all set to pick up a couple a/c line conditioners from Smart Development,,,,

    so if one were to get a decent UPS for most of the gear, would we need line conditioner after it???

    would spending money on a/c conditioners be a waste of money?? " mangling the input ?" as roughly quoted by Fletch ( hope things go well btw Fletch....


    Sanity Inn
  12. Big_D

    Big_D Well-Known Member

    Aug 21, 2004
    Quakertown PA


    You'll never get your power any cleaner or more stable than from a UPS so attempting to condition it further would be a waste. You would only be sending clean power through the conditioner and would see no change or likely muck it up. Just don't plan on moving it around much, the small one's weigh 100+lbs and the large one's can require a forklift.
  13. tony desilva

    tony desilva Guest

    Thanks for the tips on the UPSs everyone.

    So Krou, what did you find in the end? Was it the speakers or the power? Keep us posted.
  14. Davedog

    Davedog Distinguished Member

    Dec 10, 2001
    Pacific NW
    Be sure and ground the secondaries on any UPS you install...we wouldnt want you getting between potentials now would we.Also know that a UPS as well as being "uninterruptable power source" is a transformer.This is the main reason it creates a cleaner source of power.Every set of windings in an electrical grid will impart its own set of noise,phases,voltages etc....Thats why the secondary must be grounded especially if you have other integrated devices in close proximity that are not part of the UPS output.
  15. Big_D

    Big_D Well-Known Member

    Aug 21, 2004
    Quakertown PA
    Good point Dave, Another issue is when changing batteries (of course unplug the unit) but also remove the batteries leads before attempting to remove the batteries or reach into any other area of the UPS. The UPS is putting out 115 V even when unplugged because the bateries are still feeding the transformer. The batteries in all of the UPS's I have ever worked with are wired in series so you'll have to remove the positive from the first battery and the negative from the last or vice versa.
  16. Randyman...

    Randyman... Well-Known Member

    Jun 1, 2003
    Houston, TX
    The lower priced UPS units will usually just pass the AC through (filtered) to the rear AC outlets. Once an outage is detected, there is a short "switch time" to allow the circuitry to "switch" to the DC battery and inverter circuit.

    Also, the lower priced units (even up to $500) will use APPROXIMATED SINEWAVES, not true sines. Should be OK for most stuff, but a true sine is best (but also most expensive)...

    My APC Back-UPS1000 does just this - uses filtered AC power to the AC outlets, and switches to the inverter during an outage (approximated sine ONLY during the outage). This way, you can save costs of making the "online" portion a true sine-wave by passing Utility power to the outlets, but switching to approximated sinewave durind battery operation.

    I have not seen many true Sine-Wave UPS units below $500 (with any substantial VA ratings). I'd say spend the extra duckets for a true sine model, and no other power conditioning should be needed. :cool:
  17. good info on this post..

    but how come i see those furman conditioners, etc in studios alot? at my school, in the studio there, has em all over ....... there seems to be no hum anywhere in that place.. through the board, monitors, amps whatever.. it seems good... cuz they wouldnt have a UPS installed, and the 500 and down range power conditioner things would they?? or is that just dumb

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