The nitty gritty of watts and amps

AsSiMiLaTeD
AsSiMiLaTeD Posts: 11,728
edited June 2006 in Electronics
This may not be the best place to post this, but we appear to have some intelligent people in here, so I'll give it a shot. This gets a little involved, but interesting (at least to me).

OK, so we know more watts is usually better, but not necessarily all the time. From the other post I've got going on amps, we know that more amps is better also. We know how power (watts) is measured, by multiplying the voltage by the current (amps): P = V*A right????

We also know that 'not all watts are created equal', and that more amps is better on a receiver. This leads me to 2 questions:

1. Assuming that we're all living in the U.S., the standard for voltage is something like 120V right? Which means that every receiver is running with a voltage of 120 right? So the only thing that should be the determining factor in power (watts) is current, right??? (We'll leave ohms out of the equation becuase they're a constant in this little experiment) So how can two receivers be rated at the same wattage if they're running the same voltage but different current??? Say I've got a POS Aiwa rated at 200WPC and my H/K rated at 100WPC. If they're running at the same voltage, which I assume they are, how can the H/K with twice the amps be rated at only half the volts (and have 100 times the sound by they way)??? What am I missing here??? Isn't the method for calculating power ratings standardized at this point by the FCC??? Maybe Not??? Is it really in just in how they word their ratings???

2. I've heard that you have to double the power (watts) to get an audible increase in sound - that's from this website. While I don't deny that, I am currently operating under the assumption that that more watts is better (assuming the same 'quality' of watts). For example, if you had two amps, let's say two Adcoms, one rated at 100 WPC and one rated at 150 WPC, the second would produce a better sound right (assuming all other factors constant)? While it may not be louder, I would think that it would just be a little better overall, maybe with imaging and sounstage??? I've not been able to test this theory, just curious about feedback from anyone.

OK, this has gone on long enough, that is all...
Post edited by AsSiMiLaTeD on
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Comments

  • Airplay355
    Airplay355 Posts: 4,298
    edited February 2004
    1. because of the way manufactures measure watts. the POS aiwa is said to have 100 watts/channel, or in ur case 200 but they will but in little tricks that the average joe wont pay attention to. like 100 watts/channel from 100hz to 1khz. by POS aiwa receiver is rated in that way. there isnt a standardized way of ratting watts, if there was then all those boom boxes that say 520 watts!!!! wouldnt sell.

    2. the amp with 150 wpc would give u more headroom, and that would mean less stress on the amp at the same volume.
  • VR3
    VR3 Posts: 28,798
    edited February 2004
    Voltage isn't quite THAT easy.......................

    Voltage ranges from the preouts, inputs, low voltage ins and outs, high voltage, etc etc etc etc etc


    Airplay, that Aiwa probally pumps out 5 watts continuous..............maybe more?
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
  • Polkfan
    Polkfan Posts: 15
    edited February 2004
  • Airplay355
    Airplay355 Posts: 4,298
    edited February 2004
    it was enough to power two rti150s and not completely die lol never could watch a movie in surround sound with that receiver lol oh well, guess thats y its not hooked up right now.....POS
  • jdhdiggs
    jdhdiggs Posts: 4,305
    edited February 2004
    The wattage numbers on recievers and amps is generally RMS and not peak. The aiwa 100W/channel might peak at 102W, where most quality amps you'll see things like 6dB headroom or such. For a 100W amp with 6dB headroom, you'll have peak wattage capacity of 400W per channel instead of the 102W from the POS reciever.

    Also, the source tries to act as a voltage source to the speaker so whether the speaker is 1 ohm or 30 ohm, the voltage drop across will be the same, the amps will be different (I=V/R) Therefore it is not the voltage that limits the power, but the ability to provide amperage that causes the amp to clip.

    You can build circuits that build voltage above the source fairly easily, on thisng you can't do is produce more power than the wall can provide: Typically 120V and 20Amps: 2400kW If you go look at some of the high end amps, they don't go over this value for all an all channels drivin rating without special notes (dual 20 amp supplies on seperate circuits or 30amp lines) those notes mean non-standard wiring of your house.

    As for rating watts, all you have to do is demonstrate that each channel can produce the 200W, not necessarily at the same time or at all frequencies.

    Hence, 200W/Channel reciever is typically nowhere near the power of 100W/channel, all channells driven, 10hz-100khz, 6dB dynamic headroom.

    Well, I seem to have missed answering your question, but I hope you find the info usefull. So here goes:

    1). Yes
    2). Headroom is your friend

    There is no genuine justice in any scheme of feeding and coddling the loafer whose only ponderable energies are devoted wholly to reproduction. Nine-tenths of the rights he bellows for are really privileges and he does nothing to deserve them. We not only acquired a vast population of morons, we have inculcated all morons, old or young, with the doctrine that the decent and industrious people of the country are bound to support them for all time.-Menkin
  • Frank Z
    Frank Z Posts: 5,860
    edited February 2004
    After my first tube amp fiasco I was researching amplifier output ratings and found out that amplifier output is measured at 1khz. If memory serves, this a FCC/FTC requirement. I'll try to dig up the exact reference if anyone wants it.
    9/11 - WE WILL NEVER FORGET!! (<---<<click)
    2005-06 Club Polk Football Pool Champion!! :D
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
    jdhdiggs,

    6dB of headroom ? ...

    I must be living in the wrong world ... Whose have you seen that have specs like that ?
  • Frank Z
    Frank Z Posts: 5,860
    edited February 2004
    Found it! This is copied from The federal trade Commissions Website and is part of a document titled "
    Power Output Claims for Amplifiers Utilized in Home Entertainment Products." The document number is 39 FR 15387.


    § 432.3 Standard test conditions.
    For purposes of performing the tests
    necessary to make the disclosures required
    under § 432.2 of this part:
    (a) The power line voltage shall be
    120 volts AC (230 volts when the equipment
    is made for foreign sale or use,
    unless a different nameplate rating is
    permanently affixed to the product by
    the manufacturer in which event the
    latter figure would control), RMS,
    using a sinusoidal wave containing less
    than 2 percent total harmonic content.
    In the case of equipment designed for
    battery operation only, tests shall be
    made with the battery power supply for
    which the particular equipment is designed
    and such test voltage must be
    disclosed under the required disclosures
    of § 432.2 of this part. If capable of
    both AC and DC battery operation,
    testing shall be with AC line operation;
    (b) The AC power line frequency for
    domestic equipment shall be 60 Hz and
    50 Hz for equipment made for foreign
    sale or use;
    (c) The amplifier shall be
    preconditioned by simultaneously operating
    all channels at one-eighth of
    rated power output for one hour using
    a sinusoidal wave at a frequency of
    1,000 Hz; provided, however, that for amplifiers
    utilized as a component in a
    self-powered subwoofer system, the sinusoidal
    wave used as a preconditioning
    signal may be any frequency
    within the amplifier’s intended operating
    bandwidth that will allow the
    amplifier to be driven to one-eighth of
    rated power for one hour;

    (d) The preconditioning and testing
    shall be in still air and an ambient
    temperature of at least 77 °F (25 °C);
    (e) Rated power shall be obtainable
    at all frequencies within the rated
    power band without exceeding the
    rated maximum percentage of total
    harmonic distortion after input signals
    at said frequencies have been continuously
    applied at full rated power for
    not less than five (5) minutes at the
    amplifier’s auxiliary input, or if not
    provided, at the phono input.

    (f) At all times during warm-up and
    testing, tone loudness-contour and
    other controls shall be preset for the
    flattest response.
    [39 FR 15387, May 3, 1974, as amended at 65
    FR 81240, Dec. 22, 2000]

    What a mouthfull!!
    9/11 - WE WILL NEVER FORGET!! (<---<<click)
    2005-06 Club Polk Football Pool Champion!! :D
  • jdhdiggs
    jdhdiggs Posts: 4,305
    edited February 2004
    Well Done Frank! :D

    Essentially it looks like you need to write the recievers at (100WX6) is really a 12.5 W/channel, all driven with maybe 3dB of headroom.

    Granted this is the extreme low side of "twisting the ratings" but those 700W recievers don't look so impressive now...
    There is no genuine justice in any scheme of feeding and coddling the loafer whose only ponderable energies are devoted wholly to reproduction. Nine-tenths of the rights he bellows for are really privileges and he does nothing to deserve them. We not only acquired a vast population of morons, we have inculcated all morons, old or young, with the doctrine that the decent and industrious people of the country are bound to support them for all time.-Menkin
  • Airplay355
    Airplay355 Posts: 4,298
    edited February 2004
    neither do the 100wpc sony hTIB's
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
    The weak point of receivers has always been the amplifier section. How could it be otherwise without making the box 18" tall.
  • weavercr
    weavercr Posts: 289
    edited February 2004
    "6dB of headroom ? ...

    I must be living in the wrong world ... Whose have you seen that have specs like that ?" by Polkwannibe

    I do not know of any current manufactered receivers but in the late 80's both Proton and NAD used to make receivers and amps with 6db headroom. Both dropped this because of cost.
  • jdhdiggs
    jdhdiggs Posts: 4,305
    edited February 2004
    Originally posted by PolkWannabie
    jdhdiggs,

    6dB of headroom ? ...

    I must be living in the wrong world ... Whose have you seen that have specs like that ?

    to add to weaver: I have seen it on several seperate amps and that was my point. Generally amp rating include all of that information where recievers don't.
    There is no genuine justice in any scheme of feeding and coddling the loafer whose only ponderable energies are devoted wholly to reproduction. Nine-tenths of the rights he bellows for are really privileges and he does nothing to deserve them. We not only acquired a vast population of morons, we have inculcated all morons, old or young, with the doctrine that the decent and industrious people of the country are bound to support them for all time.-Menkin
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
    I wasn't questioning the fact of whether or not most amps list this statistic, only which one(s) list 6+dB of headroom as a specification.

    The specs for even most of the Class A stuff usually says something like >1.5dB, which could of course mean almost anything.

    Random examples ...

    http://www.parasound.com/products/amplifiers/hca1500aspecs.html

    http://www.parasound.com/halonew/A21details.asp

    http://www.adcom.com/specifications.htm

    http://www.bkcomp.com/pdf/Ref_200_3_2_1_manual.pdf

    http://www.nadelectronics.com/hifi_amplifiers/C272_framset.htm

    Interestingly enough manufacturers like Krell, Lexicon, Levinson etc. usually don't even list this statistic at all.
  • steveinaz
    steveinaz Posts: 19,538
    edited February 2004
    6dB of headroom would be incredible; I've never seen such an amp in my 32 years of being an audio-geek. Talk about "reserve" power..sheesh..
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
  • weavercr
    weavercr Posts: 289
    edited February 2004
    Steveinaz

    the NAD 2100 amp, I used to own one 60 watts, 6db,
    here is a link to the specs bridged mode was 100 watts with 7db headroom.

    nad 2100 power amp


    the nad 2200 amp was 100 watts 6db,
    bridged was 400 watts 5 db headroom.



    NAD 2200 amp

    and a receiver with 100w wiht 5.7 db headroom.

    NAD 7400 receiver
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
  • Tour2ma
    Tour2ma Posts: 10,177
    edited February 2004
    Originally posted by Polkmaniac
    1. Assuming that we're all living in the U.S., the standard for voltage is something like 120V right? Which means that every receiver is running with a voltage of 120 right? So the only thing that should be the determining factor in power (watts) is current, right??? (We'll leave ohms out of the equation becuase they're a constant in this little experiment) So how can two receivers be rated at the same wattage if they're running the same voltage but different current???
    This is an apples and oranges scenario. The AC voltage of the power supplied to the amp does not set the DC voltage differential the amp can produce at its speaker terminals.
    Originally posted by Polkmaniac
    Say I've got a POS Aiwa rated at 200WPC and my H/K rated at 100WPC... how can the H/K with twice the amps be rated at only half the volts (and have 100 times the sound by they way)??? What am I missing here??? Isn't the method for calculating power ratings standardized at this point by the FCC??? Maybe Not??? Is it really in just in how they word their ratings???
    As Frank posted the FTC has a standard, but I believe it's for 2 ch with a rule for "multi" channel being readied. You can comply and still quote other measurements.
    Power output (watts) is most often stated as RMS (root mean square) output voltage times the resistance applied to the amplifiers output. HCC (High Current capacity) is generally reported as peak to peak.
    Even the NAD's weavercr posted switch to the "IHF" (Institute of High Fidelity) standard for their headroom calc's. This is an old standard the audio industry developed themselves in part to forstall FTC regulation.
    You also asked about sound quality. Obviously design, component and build quality are all in play.
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner

    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
  • Kpt_Krunch
    Kpt_Krunch Posts: 52
    edited February 2004
    Just to throw in my 2 cents (literally) on amps - I have an HK520 rated at 75 WPC all channels driven (5) and 85 WPC two channel driven. Sounds unimpressive doesn't it? The HK520 also has a High Current Capability (HCC) rating of +/- 45 amps. When I demo'd this AVR vs. others (Sony, Pioneer (Not Elite), Yamaha (this was close though) ) and a few others I can't recall now, well it wasn't even close.

    And just to speak 'english', the difference at reference levels is not how 'loud' it is, but how it sounds. All the above mentioned receivers could not get close to the HK520 before audible distortion set in. The HK played much louder then all of them save the Yammy (the Yammy still wasn't up to par with the HK, but it was a lot closer then the other receivers) before distortion was noticable.

    This was a few years ago, and I was comparing price points. I know Pioneer Elite, Denon's (which were not sold where I demo'd) and other companies make receivers that are much better than the H/K, but I find for the price range of the 520 this was the best receiver out there. It was the amp difference, not the 'watts'.

    I guess the best way to say summarize this is they are called "Amplifiers', not "Wattafiers". I don't even look at watts anymore, and if I can't find an amp rating on an AVR, I don't even waste my time listening, as it isn't worth it.
    AVR - HK520
    Amp - HK PA2000
    Fronts- Energy Reference Connosieur RC-70
    Center - Energy Reference Connosieur LCR
    Surround - Energy Reference Connosieur RC-10
    Sub - SVS PBU-13 Piano Black
    Samsung HLN617W
  • mantis
    mantis Posts: 17,204
    edited February 2004
    This is one reason I say forget about the spec's to a point.They don't tell the whole story and most of the time lie there face off.

    Sound quality has nothing to do with spec's.You can read about juicy spec's and the gear can sound like ****,why????Because most companies love to play"the numbers game".As some of you realized,they don't always tell the whole story like rating one channel driven at 1k......all channels driven from 20 to 20,and how about current,this amp has 75 amps per chanel,then you look at a receiver with the same watt rating and only has 7.5 amps per channel...........good **** huh

    Spec's are Important to the level that If you have hard to drive speakers like 6 or 4 ohms with a low 89 or lower db rating,then making sure the amp has the nessary amount of current and is stable driving the load.

    massive power rated amps don't aqlways sound better.I have heard many 60 watt to 100 watt rated amps sound so much better then 250 watt rated amps......and so on and so on.

    I say listen with your ears,after you figure out that the amp can safely drive your given speakers,it's only a matter of time that you figure out what amp/pre/receiver sounds best.

    Such a rough world out there...........****!!


    Dan
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
  • jdhdiggs
    jdhdiggs Posts: 4,305
    edited February 2004
    Originally posted by steveinaz
    6dB of headroom would be incredible; I've never seen such an amp in my 32 years of being an audio-geek. Talk about "reserve" power..sheesh..

    I saw it a couple times on some amps while doing research on them. The 6dB's are out there, but really rare...
    There is no genuine justice in any scheme of feeding and coddling the loafer whose only ponderable energies are devoted wholly to reproduction. Nine-tenths of the rights he bellows for are really privileges and he does nothing to deserve them. We not only acquired a vast population of morons, we have inculcated all morons, old or young, with the doctrine that the decent and industrious people of the country are bound to support them for all time.-Menkin
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
    NAD was known for stretching their stats in this area using some sort of snake oil calculation that was recognized by no one but their own marketing staff ...
  • gidrah
    gidrah Posts: 3,049
    edited February 2004
    I thought they were known for under rating their continuous power rating.

    Mantis is right. Specs can get you into the ballpark. Specs can also impede you from melting something. Unfortunately, they can also give a drunken member a sense of over confidence. Did I ever tell you how I blew a mid/woof in a pair of 10Bs (200 watt?) when comparing them to a pair of vintage 30 watt speakers?
    Make it Funky! :)
  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited February 2004
    Don't get me wrong. I like NAD gear, but to believe any amplifier has 6dB of headroom I'd have to see it on a bench.

    Others who have taken the trouble with the appropriate test equipment could not validate the claims AFAIK and there have been numerous threads in the past regarding this which is one of the reasons why NAD has toned down some of those claims on their more recent products.

    After all we don't really believe that they either forgot how to make amps with this much headroom or that they no longer thought it was a good idea, do we ?

    As far as melting speakers goes, one can trash almost any speaker using almost any amp. Just turn it all the way up and leave it there and eventually you'll find a movie or music passage that will do the trick.
  • gatemplin
    gatemplin Posts: 1,595
    edited February 2004
    I'm confused. Say an amp has 100W per with 6 dB headroom. Doesn't that mean it really has 400W?
    Graham
  • jdhdiggs
    jdhdiggs Posts: 4,305
    edited February 2004
    No, it would mean that it could sustain 100W of power into the speaker, but have temporary bursts of up to 400W without clipping if I am recalling everything correctly.
    There is no genuine justice in any scheme of feeding and coddling the loafer whose only ponderable energies are devoted wholly to reproduction. Nine-tenths of the rights he bellows for are really privileges and he does nothing to deserve them. We not only acquired a vast population of morons, we have inculcated all morons, old or young, with the doctrine that the decent and industrious people of the country are bound to support them for all time.-Menkin
  • Tour2ma
    Tour2ma Posts: 10,177
    edited February 2004
    Ed Zachery... headroom is short-term power for music transients.

    Headroom is just not a term that you hear much anymore. Once it was "the" stat for amps. For a while it seemed that everybody's amp had at least 3 dB of it. NAD, Adcom and Proton all beat the headroom drum loud and long.

    But in parallel with the headroom craze watts and current just got so damn cheap that headroom just wasn't an issue. I mean my poor old M-1.5t only had ~1.2 dB's of it. Ultimately raw power won out...

    As for NAD, as I said above, they jump shifted to the old ihf standard for their headroom rating. The ihf rating system was ultimately insufficient to stave off FTC rules as it was too easily manipulated.

    That said, having once again heard NAD amps at Russ', I was reminded how much I liked them back when headroom was cool.

    Stat's have their place and are quite useful in narrowing the field.

    As for trashing a speaker, hell you don't even need an amp. Just wire it to a wall socket...
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner

    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
  • Dennis Gardner
    Dennis Gardner Posts: 4,861
    edited February 2004
    As for trashing a speaker, hell you don't even need an amp. Just wire it to a wall socket...
    I've seen this done with raw drivers in an auto stereo store.
    That 55-60hz hum is quite something to see on some of those
    15-18" models that can handle the burst, then blow the cone out of the lesser speakers 20 feet into the air.

    Talk about extreme marketing!

    :D

    DG
    HT Optoma HD25 LV on 80" DIY Screen, Anthem MRX 300 Receiver, Pioneer Elite BDP 51FD Polk CS350LS, Polk SDA1C, Polk FX300, Polk RT55, Dual EBS Adire Shiva 320watt tuned to 17hz, ICs-DIY Twisted Prs, Speaker-Raymond Cable

    2 Channel Thorens TD 318 Grado ZF1, SACD/CD Marantz 8260, Soundstream/Krell DAC1, Audio Mirror PP1, Odyssey Stratos, ADS L-1290, ICs-DIY Twisted , Speaker-Raymond Cable
  • Ceruleance
    Ceruleance Posts: 991
    edited February 2004
    hmm so if the wall socket is 120v and your driver is two 8 ohm voice coils wired in series, for 16 ohms total, you would get 7.5A current pull and would be throwing 900 watts at the driver?

    Am i doing this right? 900 watts isn't unheard of for power handling, as long as the coils really are 8 ohms. If you have dual 2 ohm coils you are looking at like 3,600 watts..

    someone confirm to me that I passed high school physics and it wasn't a fluke