Results 1 to 6 of 6

Thread: Amp power draw

  1. #1
    The Great
    Join Date
    Aug 2004
    Location
    Walnut Creek, CA
    Posts
    5

    Amp power draw

    I have a question that's more technical overall so I thought I would post here.

    I recently purchaced parts for a Sub project: Dayton Titanic MkIII 15" driver, Velodyne SPL-II amp, Def Tech PF15TL+ case. I can't justify the labor or cost for this reason: 50 watts. That is the max draw I'm getting on the SPL amp no matter how hard I push it according to my watt meter (Kill-a-watt basic, a crappy gadget for this I know, but it reads somewhere in the realm of where the draw is.) I started wondering about this after looking into getting a Crown XLS5000 amp and it only had a theoretical draw capacity of 2200-2400 Watts (110-120V x 20 amps) and that amp is rated for 2500 watts *per side*.

    On a side note: the Velodyne amp is positively whimpy compared to the amp in the Def Tech which is double the size & WAY better built. The Velo amp is weighs in a whopping 7 lbs tops (including the plate) and is supposedly double the power. I don't really believe it at all (they seem equally matched power-wise,) hence my question.

    So what's the deal? How are these amps "rated"?

  2. #2
    Audio Hobbyist Since 1969 Glen B's Avatar
    Join Date
    Dec 2001
    Location
    New York
    Posts
    517
    Amplifiers draw current in pulses. I opine the 50 watts you're reading for the SPL amp is only a continuous average current draw. The response of the Kill-A-Watt is not fast enough to read and display the peak current draw. With regard to the Crown amp, it is rated at 2,500 watts per side @ 2 ohms, but remember that is peak power, not continuous power. It is possible for an amp to deliver that much power into the load for a few milliseconds -- a 20A circuit will deliver the necessary current needed by the amp for a few milliseconds at a time without tripping the breaker.
    Last edited by Glen B; 08-25-2010 at 12:16 PM.

  3. #3
    ISCET CET, FCC CTT, USITT Dual-500's Avatar
    Join Date
    Nov 2003
    Location
    Fort Worth
    Posts
    221
    What Glen said for starters.

    Music has a peak to average ratio of somewhere in the neighborhood of 5-1 to 10-1 depending upon the program material.

    An amp is ~70-90% efficient in terms of output -vs- input and the power supply stores energy - more for old school vintage amps. The stored energy in the power supply will smooth out the line surge demand for the amp. The energy lost in the amp is heat.

    The (efficiency of the amp) x (demand in output) to the speakers will determine the line demand of the amp at any given time. There will be a slight lag in current demand caused by the energy stored in the power supply. The lag is short in terms of time and would take test equipment to measure and mentioned for reference only.

    As far as manufacturer amp ratings go, you already pretty much summed it up: "On a side note: the Velodyne amp is positively whimpy compared to the amp in the Def Tech which is double the size & WAY better built. The Velo amp is weighs in a whopping 7 lbs tops (including the plate) and is supposedly double the power. I don't really believe it at all (they seem equally matched power-wise,)"

    With amps, essentially it boils down the Size Matters all other things equal. And, quality is quality. I would agree with your assessment of the two amps without seeing either given they likely have the same basic technology within them.
    Last edited by Dual-500; 08-26-2010 at 10:25 AM.

  4. #4
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
    Join Date
    Jul 2002
    Posts
    6,826
    Quote Originally Posted by themblues
    I have a question that's more technical overall so I thought I would post here.

    I recently purchaced parts for a Sub project: Dayton Titanic MkIII 15" driver, Velodyne SPL-II amp, Def Tech PF15TL+ case. I can't justify the labor or cost for this reason: 50 watts. That is the max draw I'm getting on the SPL amp no matter how hard I push it according to my watt meter (Kill-a-watt basic, a crappy gadget for this I know, but it reads somewhere in the realm of where the draw is.) I started wondering about this after looking into getting a Crown XLS5000 amp and it only had a theoretical draw capacity of 2200-2400 Watts (110-120V x 20 amps) and that amp is rated for 2500 watts *per side*.

    On a side note: the Velodyne amp is positively whimpy compared to the amp in the Def Tech which is double the size & WAY better built. The Velo amp is weighs in a whopping 7 lbs tops (including the plate) and is supposedly double the power. I don't really believe it at all (they seem equally matched power-wise,) hence my question.

    So what's the deal? How are these amps "rated"?
    I will tell you this much, the more power you give to a subwoofer, the better it will sound. Bass frequencies require a lot of power to get the deep bass in the room, and the more power you have the less chance of overdriving the amp, which lowers distortion, and makes for better sound quality over all. The Velo's use DASH amp, so its size will tell you very little about its power output abilities.

    What Ohm rating are you testing the SPL II amp?

    (must be hot as hell in Walnut Creek, cause it is hot as hell in San Leandro!)
    Sir Terrence

    Titan Reference 3D 1080p projector
    200" SI Black Diamond II screen
    Oppo BDP-103D
    Datastat RS20I audio/video processor 12.4 audio setup
    9 Onkyo M-5099 power amp
    9 Onkyo M-510 power amp
    9 Onkyo M-508 power amp
    6 custom CAL amps for subs
    3 custom 3 way horn DSP hybrid monitors
    18 custom 3 way horn DSP hybrid surround/ceiling speakers
    2 custom 15" sealed FFEC servo subs
    4 custom 15" H-PAS FFEC servo subs
    THX Style Baffle wall

  5. #5
    Forum Regular blackraven's Avatar
    Join Date
    Nov 2006
    Location
    St. Paul, Minnesota
    Posts
    5,421
    The Velodyne uses a Class D amp. You can't judge it by its weight. It's a digital amp and they weigh very little and generate little heat. I've heard the spl velodynes and they put out plenty of power. You can't judge a book by its cover!

    The Velodyne amp is 95% efficient and is rated at 1,000 watts RMS and 2,000 peak!

    http://www.velodyne.com/vproducts/do...eries%20II.pdf
    Pass Labs X250 amp, BAT Vk-51se Preamp,
    Thorens TD-145 TT, Bellari phono preamp, Nagaoka MP-200 Cartridge
    Magnepan QR1.6 speakers
    Luxman DA-06 DAC
    Van Alstine Ultra Plus Hybrid Tube DAC
    Dual Martin Logan Original Dynamo Subs
    Parasound A21 amp
    Vintage Luxman T-110 tuner
    Magnepan MMG's, Grant Fidelity DAC-11, Class D CDA254 amp
    Monitor Audio S1 speakers, PSB B6 speakers
    Vintage Technic's Integrated amp
    Music Hall 25.2 CDP
    Adcom GFR 700 AVR
    Cables- Cardas, Silnote, BJC
    Velodyne CHT 8 sub

  6. #6
    The Great
    Join Date
    Aug 2004
    Location
    Walnut Creek, CA
    Posts
    5

    Great!

    That has put all my fears to rest. In that case I may continue the project! Thanks!!!

    In the amp comparisons, thanks as well. My feeling is that the Velo and the Def Tech are equally matched as far as SQ and SPL. The Def Tech hammers out some serious bass for a 500W rating and the amp is built like a tank.
    Last edited by themblues; 08-26-2010 at 10:04 AM.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •