Measuring System Amperage Draw

Discussion in 'Archived Threads 2001-2004' started by Bill Kane, Jun 14, 2002.

  1. Bill Kane

    Bill Kane Screenwriter

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    I was in Good Guys today and stopped in their primo show demo room where Star Wars-TPM was booming away in the race scenes.
    As far as I cud tell, the equipment included a 75-in RPTV, Denon 5803 AVR, Energy Veritas mains and Energy e:XL sub (150W RMS). What caught my attn was the Monster AVS2000 power center with digital voltage and amperage readouts.
    Voltage appeared to be being boosted and read 121V to 122V. What was most interesting was watching the ammeter read during peaks. I'm thinking the Sub also was plugged into the AVS2000 because peak amps seem to coincide with the most dynamic thumps.
    The ammeter read on the average 8.0 amps during relatively quiet scenes but peaked to 10.5 amps in dynamic passages. I wud estimate that sound level output was at least 75dB. Denon 5803 volume read -8, whatever that signifies.
    So here's "high-end" consumer amps being run fairly open with demanding 5.1 and drawing current well within a 15A household circuit's safety zone capability (12A).
    ...my unscientific observations.
    Luke Ampwatcher
     
  2. Chu Gai

    Chu Gai Lead Actor

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    Interesting. I wonder how that current draw compares with the various things that were hooked up? Hmmmmmm...I wonder if Yentl draws more current [​IMG]
     
  3. Frank_S

    Frank_S Supporting Actor

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    I had an electrician perform a load test on my system at home. All of my equipment below was turned on and running at blaring reference level, louder than I would normally listen. I used the Omaha Beach chapter of SPR(DTS) for the test, about 20 minutes long. My system at idle drew 7.5 amps, during the loudest peaks it drew only 9.5 amps. Everything is connected to (1) 15 amp circuit. I plug all my gear into 2 Richard Gray Power Company units. Below is a list of my equipment that was on during the test, FYI.

    Toshiba TW40X81 RPTV
    Toshiba SD-5109 DVD player
    Toshiba DST-3000 Hi Def. receiver(Always on)
    Classe SSP-25 pre/pro
    Aragon 8008 x 3 (3 x 200 wt/ch)
    Aragon 8008 BB (2 x 200 wt/ch)

    B&W Nautilus 804(mains)
    B&W HTM-2 (center)
    B&W 602S2(surr)

    SVS 20-39 PC sub(LFE)
    Rel Storm III sub(mains)
    B&W AS6 sub(surr)

    All plugged into 2 RGPC units and (1) 15 amp circuit.
    Nothing else ever runs on this circuit except a hallway light. Dedicated lines are good if you share power with appliances on the same circuit as your audio system.
     
  4. Bill Kane

    Bill Kane Screenwriter

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    Frank, thanks for popping in...I believe yopu've posted this info before, and it was in the back of my mind as I described what I saw in the store.

    As I said, I cudn't follow every wire path in the store set-up. But as you experienced, I thot it instructive that ordinary 15A household circuits (proviso: virtually nothing else using it) should be perfectly adequate.

    Hey, I won't knock a dedicated 20A circuit: more power to the user! But it's not necessarily a mandatory upgrade.

    I've read Richard Grays website, but still am unclear if it's a voltage stabilizer and/or balanced power device if either.

    So with the passle 'o gear you had operating (!) and seeing 9.5 peak amp draw, do you think the RG modifies/mitigates or smooths current demand?
     
  5. brucek

    brucek Second Unit

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    Bill,
     
  6. Bill Kane

    Bill Kane Screenwriter

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    Bruce, nicely put. We always appreciate the time you offer on this (and other forums) to delve into EE/Technology aspects of HT. Who knows, it may rub off on some of us[​IMG]
    Before I go on, you might consider polishing your post, perhaps under the heading "Do I Need a Dedicated Circuit?" for inclusion with Vince Maskeeper's assistance in the HTF's Primer in Basics.
    I just thought it was instructive for the majority of folks who don't build dedicated HT rooms (thus don't have the opportunity to tailor their circuits in an open-wall situation) and are at the mercy of what circuits come with their homes and apartments.
    I do recommend that people find out what else is on the circuits they use for HT by throwing the breaker. As you note, it's inadvisable to run our HT electronics on home circuits that also power frigs and other appliance motors, fluorescents, dimmers, computer stations and the like.
    (I lucked out in that my subdivision house was built with 20A circuits. The one I am using for HT has two outlets in the LR. I plug my 170WPC RMS amp directly into an upgraded receptacle, the surge protector into the other prong and my Sub via a small surge unit into the second outlet. Two 50-watt floor lamps on this circuit flank the HT. This circuit also feeds my master bedroom, but the lights there are turned off 99 percent of the time I am powering the HT).
    And I would want a dedicated circuit before I go to the expense of buying a "power conditioner" above and beyond surge protection to ensure I'm starting with the cleanest electrical power path in the first place.
    Yes, without a professional electrician, I do not know how my existing circuit is legged or phased at the panel.
     
  7. brucek

    brucek Second Unit

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    Bill,
    Thanks for the kind words.
    Marrettes are small copper cone-shaped springs covered in a piece of hard plastic used to connect solid copper wire together without solder or screw clamp. You will find them inside every wall receptacle box in your house where the circuit continues to another box. They're color coded for the size of wire you're connecting.
    Once you've stripped the insulation off a couple pieces of electrical wire, you insert them in the marrette and twist. The spring drags the wire up inside and holds the two pieces of wire together. Theoretically this makes a cold weld, but it doesn't take much to do a bad job, or, after someone has dragged the receptacle in and out of the box several times, or, by simple age causing oxidation, for these wire joints to become slightly resistive. A receptacle at the end of a circuit run could theoretically have gone through at least eleven of these connections before it gets to the receptacle that is used in an HT.
    That last receptacle might measure 120 volts OK with a meter with no load, but there's a potential for quite a voltage drop because of those resistive joints when you draw 10 amps through that run. This is one of the main reasons for a dedicated circuit.
    Anyways, I suspect you knew what a marrette was, but didn't know the name. [​IMG]
     
  8. Bill Kane

    Bill Kane Screenwriter

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    Canada: marrette

    U.S. = wire nut
     
  9. brucek

    brucek Second Unit

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    [​IMG] [​IMG] brucek
     
  10. Wayne A. Pflughaupt

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  11. Mark Tranchant

    Mark Tranchant Stunt Coordinator

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    Live in the UK. [​IMG]
    Not only do we have decent chunky wall sockets and plugs (three chunky copper pins, including a decent earth), but the 240V (-ish) mains voltage rating makes line resistance less critical (as power loss is I²R, and I will be smaller for a given power). The standard wall socket's 13A maximum rating provides over 3kW of power.
    Noting that some ultra-top-end preamps are battery powered, I've often pondered the merits of a UPS (uninterruptible power supply) device to power the system - one that always uses the battery output rather than one that switches on power failure.
    Of course, another advantage of living in the UK is that shipping is cheaper on all decent equipment, as it comes from here in the first place... [​IMG]
    (retreats to find asbestos suit)
     
  12. Wayne A. Pflughaupt

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    Here’s a good one for you, brucek:
     
  13. brucek

    brucek Second Unit

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    Hey Wayne,
    Actually, that would seem about right for that integrated amp.
    First, as you already know, power amplifiers aren't 100% efficient. Class A are about 50% and Class AB are about 70%. This is evidenced by the heat generated in their heat sinks. Any heat generated within the amplifier itself including what's dropped across the output stage isn't being dissipated in your speakers. This inefficiency must be added to the total power drawn from the wall.
    Certainly in older equipment, instead of the negligible current drawn by LED indicators, they used light bulbs. These draw a lot of current. They must also be added to the total.
    An integrated amp of that era had a lot of discrete components including most of the components that would be using power in the preamp section.
    And finally, there's always a margin of safety added for the consumer, so they won't overload their household circuit by relying on the value posted as power required from the wall.
    So, altogether, for an old 30 watt per channel integrated amp, 220 watts isn't out of line as a specification... [​IMG]
    brucek
     

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