100 Amps? 75 Amps?

Discussion in 'Archived Threads 2001-2004' started by John*K, May 12, 2002.

  1. John*K

    John*K Stunt Coordinator

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    Hello -

    I've been interested in an amplilfier to mate with my Harman Kardon AVR 7000. I sent in a question to tech support at Harman asking about the Signature 2.1 -- I mentioned that I had always heard that more amplification would provide better sound. However, in this case, since the AVR 7000 and the Signature 2.1 are both rated at 100x5 WPC, I was doubtful that there would be a performance gain.

    He pointed out that the 2.1 had 100 amps, while the AVR had 75 amps. Even though they both have 100 watts.

     
  2. Shawn Solar

    Shawn Solar Supporting Actor

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    I am not sure how they can get 100amps out of a 15amp circut. I think 15amp=1800watts and 20amps=2400watts so 100amps would equal 12000watts. Kind of funny actually. Check on the back of the reciever to see power comsumption. I bet it is around 3-4.5amps.Which alot is turned into heat some is used to power the pre-amp section.

    When I added a 2-channel amp(anthem mca-2) to the front end of my system there was a huge difference. For one the high end of my paradigms reference 40's went from slightly bright to very neutral. vocals and instruments seemed to have more space and extended further into the room. My reciever is a Marantz sr-7000. I can't wait to get the 3-channel version for the rest of my speakers.
     
  3. John Royster

    John Royster Screenwriter

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    HK has always used high current amplification. I've owned many and personally love them.
    But to answer your question 100 or 75 amps means peak. So while the amp is not able to continously output this current, its fine...it doesn't need to. I'm sure some of the other guys could give you a better explanation.
    And anybody that doubts the current capabilities of HK amps needs to bench one. The one way I'm sure of it was the size of the arc when I was stupid enough to move speaker cables with the amp putting out a good volume. dumb, dumb, dumb. Big, thick blue-white arc. poor amp never did work right after that. [​IMG]
    PS - watts are a measure of power, but current is what does any kind of work. ie moves your speakers.
     
  4. Peter Johnson

    Peter Johnson Stunt Coordinator

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    He's full of it.

    An amp is a voltage source. It provides a voltage over a load, which according to ohms law, dictates current.

    "The SIG 2.1 amplifier puts out 100 watts per each of the 5 channels @ 100 amps of current and the AVR7000 puts out 100 watts per channel @ 75 amps of current. There is a 25 amp difference, so of course the SIG 2.1 has more power,"

    Power is dictated by P = (V^2)/R = (I^2)*R

    V is fixed as the rail voltage/SQRT(2).

    I am of the opinion that amps do sound different, but specs are specs..and he is full of crap.

    "High Current" is PURELY a marketing terms. Means nothing.
     
  5. Kevin P

    Kevin P Screenwriter

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    The higher the current rating of the amp, the better the amp can handle a low impedance load (say, 4 or 2 ohm speakers), or low efficiency speakers. As impedance drops, at a given voltage level, amps (and thus watts) rise, until the amp reaches its current limit and voltage drops, which leads to clipping and other nasty stuff.

    Watts are just a convenient way to rate an amplifier's output power as a single number. The real numbers are volts (V) and amps (A). The higher the voltage, the more amps you'll get at a given impedance level, which is why on quality amps you'll get more watts into a 4 ohm load than an 8 ohm load. If an amp doesn't put any more power into a 4 ohm load, then the amp is limited by the amount of current it can produce.

    For an amp to send 100 amps to 8 ohm speakers, the amp would have to output 800 volts. 800 volts at 100 amps = 80,000 watts! Instead, 100 amps is probably the maximum rated output level of the amp before its output transistors fry, meaning it's pretty heavy duty. It won't ever produce 100 amps under normal use. Maybe 10 amps peak.

    KJP
     
  6. Gifford L

    Gifford L Agent

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    Those current specs are instantaneous or peak values and HK doesn't give any kind of duration for those specs. I suspect it like a microsecond or so for those values. But the signature amps bigger spec does tell you that the power supply is probably bigger and better than the 7000's so the comparison isn't meaninless IMO. The 7000's power supply while good for a receiver is nothing to write home (the anthem MCA 2 has a bigger transformer for 2 channels than HK is using for 5) about so while a seperate amp is better I'm not sure if it would be worth it.

    Stepping up to am amp like an Anthem or B&K or Rotel or Outlaw in the neigborhood of 150-200 watts would be in my opinion. In other words I'm not positive about the 2.1's capabilities but if your going to upgrade make sure it is significan't and worth your while.

    BTW you can get more than 15-20 amps from a device plugged into a wall socket, just not more than that being pulled from the socket at 120 volts.

    When you use a step down transformer (like the one in an amplifiers power supply) you step down the voltage and increase current capabilities. The wattage stays the same (except for what is lost in heat) between the primary and secondary windings. So using a 2:1 step down transformer your 120 volts and 15 amps on the primary becomes 60 volts and 30 amps (minus whatever is lost of course). 1800 watts on the primary (120V 15amps)and 1800 watts on the secondary (60 volts and 30 amps)
     

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