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Power rating : peak or RMS?

Discussion in 'Amps and Cabs [BG]' started by Inconnu, Mar 17, 2013.


  1. Hi!

    I used to read, back in the days, both peak and RMS power ratings on amps specs sheets. Today, I usually read a power rating, measured in watts, but it's not specified if its either the "peak" rating or the "RMS" rating.

    My question : which is it???
     
  2. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    INCOMING!!!

    Can-Of-Worms.
     
  3. hahahaha.

    Generally RMS.
     
  4. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Some people will argue that they're all meaningless but this is the standard that amp makers have adopted so we have to deal. Unless it specifically says RMS for the wattage, it's suspect. There have been cases of manufacturers quoting peak wattages for their amps without denoting it, and there have been cases of manufacturers simply making up a number out of thin air because they believed their amps "sounded like a higher wattage amp." But I'm finding through the independent testing that people have done on different amps that by and large, RMS and peak wattage quotes are pretty accurate in most manufacturers as long as they specify RMS or peak. If they don't specifically use those terms, then there's almost always something hinky going on.
     
  5. Wattage is a pretty flower that smells BAD
     
  6. OK, ok, sorry I asked...:D
     
  7. Steve Dallman

    Steve Dallman Supporting Member

    Peavey, who was always clear of their RMS ratings have abandoned that. The class D bass amps are listed in Peak watts, with RMS being half the peak rating. That Peavey 600 watt class D bass head is only 300 watts RMS. I'm sure other class D amps of theirs are similar. I think this change, without explanation, is nothing short of deception. I will complain in writing to them, being a longtime PV owner. Vox did this with their 60's SS Thomas Organ amps. Most companies since I started playing in 1967, that exaggerated their power ratings by stating only peak watts went bust.
     
  8. It is not true with all class D/SMPS amps. Bass Gear Magazine tested the G-K MB800 and it exceeded (slightly) it's 800 watt "rms" at 4 ohm rating and on sustained burst tests exceeded 1 kw. Quick check of an available street price showed $699.00. If you paid $699.00 in 1970 that same item would cost $4,182.58 in today's money. While $700.00 is a lot of money it is know where close to $4,182.00. That makes the product pretty inexpensive in prospective.
     
  9. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Ya, class D follows a different set of rules apparently. It's not uncommon to see Bass Gear bench tests where the micros may just have a few watts available past the RMS wattage.
     
  10. Hi.

    :confused:

    That abandonment of clarity has had to occur pretty early since the "Peavey watts" have been around since 70's AFAIK.

    Regards
    Sam
     
  11. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    i thought RMS was a standardized thing, peak x 0.75. is this wrong? i still only use "watts" as a category. like "under 100" or "over 300" or "500+". that's about all i consider (when looking at watts) when i'm shopping, RMS or not.

    flame suit on. fire extinguisher handy. light it up, techies. gimme the hard truth ;)
     
  12. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
  13. nysbob

    nysbob

    Sep 14, 2003
    Cincinnati OH
    The only rating that ever meant anything to me is RMS, but at this point I don't care because I use only amps that have seasoned for 30 years and have iron transformers. They have sufficient grunt for my purposes.
     
  14. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    B-string, the next time I'm going to the left coast, I must find you and break bread.

    To me, it all depends on the company. I feel that some companies (GK comes to mind first) rate their amps very conservatively. In other words, the official work horse of the 80s, the 800RB probably regularly put out more than that. (I know it sounded like it did anyway.) While some companies (to avoid flames I will keep my suspects to myself) will use peak to squeeze a bit more marketing out of their product. So then, if you go into Brad X store, and you see that QualityCo amps sell for $1,000 for an 800 watt amp, and CraopCo amps sell for $600 for a 1,000 watt amp, you will say to yourself "Self, the CrapCo amp seems like a better deal, because obviously it is much louder and cheaper." When that may not be the case at all.

    All that being said, I will throw out the obligatory "Watts mean sqaut. There's more to it than that. It depends on your speaker cab. Yada yada yada. Quit worrying about numbers and go play the rig or read some reviews if there's nowhere to play one locally. Blah blah blah Check out the sticky section."

    Glad we got that official statement out of the way.
     
  15. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    i like when people on CL put the watts rating for the power supply up thinking it's the amp's watts rating. like the "600 watt peavey renown" i saw the other day. sweet.
     
  16. Be my pleasure :D I know where to get a fine french loaf, crisp but flaky crust and wonderful soft body :p.........oh yeah bread. :D
    That's not why you called though? :)

    Always fun to break some bread and meet new people, swap gig war stories ect.
     
  17. It's close but not quite right. RMS stands for Root Mean Square and for a sine wave it is the peak value divided by the square root of two or, equivalently, multiplied by 0.707.
     
  18. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, Chopshopamps.com
    well......my memory has a 5% margin of error overall, so....
     
  19. dincz

    dincz

    Sep 25, 2010
    Czech Republic
    This adds to the confusion. Power is calculated from RMS voltage and current. The result is in watts - not RMS or anything else, just watts. There is no such thing as RMS power. To get RMS voltage or current, multiply the peak value by 0.707. This number is not relevant to power.

    The convention is that when manufacturers state power in "RMS" watts, what they really mean is the continuous power rating i.e. the power output that can be maintained for several minutes or more without damage.

    Burst power ratings indicate power output available in short bursts - milliseconds rather than minutes.

    In short, unless the manufacturer states the measurement method (and they should but usually don't), then the figures don't tell you much.
     
  20. Actually not damage, instead at the rated distortion figure. The higher the distortion threshold the higher the power output. Typically for MI amps <5%, some <1%.
     

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