Where to find HONEST power ratings??

Discussion in 'Amps and Cabs [BG]' started by PatentNonsense, May 19, 2012.

  1. I've been amazed to see how many head and amp manufacturers publish false power numbers. Here's how I figure that:

    A residential wall socket in the US will be fused for 15A - maybe 20A in a commercial building. 15 amps at 120 Volts is 1800 Watts at most. That 1800W has to cover everything else on the same circuit, plus the fan AND any waste heat the unit puts out. If somebody says their amp is rated for more than 1800 Watts in any configuration, but can be plugged into an ordinary wall socket, they aren't being truthful. I'm not talking about "peak power" or "program power" numbers - we all know those numbers are BS, so they don't fool people - but the unconditionally stated power. I've seen one manufacturer warn that a 20A circuit is required for their highest-powered model, and maybe a manufacturer could measure power with line voltage at the high end of tolerable - say 130V - but that still implies an absolute ceiling of 2600 Watts. So I think that claims to (for example) 6000 Watts out a unit with an ordinary wall socket are false. If the ratings on a manufacturer's top-end units are inflated, then I don't believe any of their ratings.

    1) Are there any manufacturers who do publish honest power ratings?

    2) Has anybody published actual power measurements?

  2. B-string

    B-string Supporting Member

    Bass Gear Mag does with every amp they test.
  3. packhowitzer

    packhowitzer 155mm of pure destruction

    Apr 20, 2011
  4. Bassamatic

    Bassamatic keepin' the beat since the 60's

    It's kind of like the old days of hi-fi, where battery powered boom boxes had 1000W! (from 8 D cells, of course). This is why the IHF came up with a standard for measuring hi fi amps. Perhaps the same needs to be done with instrument amps.
  5. beans-on-toast


    Aug 7, 2008
    Rule number one. Assume that everybody lies.

    Some products don't measure up and the manufacturers make creative claims that don't stand up to performance in the real world.
    Some products exceed their claim so they sound better than the competition.
    Some products perform as claimed.

    You never know where the truth lies.

    So find an amp that sounds fantastic. Forget about the specs. Trust what you hear.
  6. B-string

    B-string Supporting Member

    I'm waiting for agedhorse to post his education on available power from 120VAC 15 amp circuit again. The man does it so well, it is always a pleasure to read. :)
    (Hint: more than 1800 watts available for audio use)
  7. chatterbox272


    Apr 12, 2012
    Also remember that other parts of the world have different outlet EMF (voltage is actually the amount used, whereas EMF is the max available). Here in Australia where most people have 240V outlets, theoretically we could have a 3600W amp. If they want to inflate numbers they can just test it from a 240v. Although I have never seen an amp with a 6000W RMS.
  8. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I just quickly browsed one set of power ratings at the QSC web page, and the numbers were qualified as follows:

    EIA 1 kHz 1% THD
    * Burst mode testing required due to AC service current limitations

    I'm more than willing to bet that these are honest ratings. The 1% THD qualifier doesn't give much room for fudging the numbers.
  9. will33


    May 22, 2006
    A tech could explain it better than me, but, there is "duty cycle", the fact that the amp isn't asked to push all that juice all the time, and the fact that the caps store, discharge, then recharge again.

    Amps can produce more than the wall socket can deliver continuously, if they aren't asked to produce all that power continuously.

    Hartley Peavey as a good laymens writeup about this, using a toilet analogy, which is fairly easy for most everybody to understand.

    Chapter 4 of the whitepapers. http://www.peavey.com/support/technotes/
  10. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    1) Just about NOBODY's amp will produce full rated power continuously..... Some amps, like a PLX, will actually damage internal components if asked to do so...... AND QSC is VERY good about ratings.

    Most don't have the heatsinking to produce continuous full power, OR the transformer capability to do it.... many SMPS amps are worse about that than the "heavy iron" units.

    2) For your purposes, it makes NO DIFFERENCE if the amp CAN or CANNOT produce full power continuously, because there is no musical reason to do it..... You are not driving a shaker table, and even the most hard core thrash band has pretty much no use for a sine wave at high power.......

    3) If an amp COULD produce the rated power for at least a reasonable time IF the outlet would allow the current, THEN I challenge anyone to make a valid claim that the spec is bogus.....

    I will name one amp that I am pretty sure WILL produce full power for longer than you want to worry about it...... An Ampeg SVT will put out full power for about as long as you care......

    Most SS amps, and many tube type will NOT do that.
  11. Tuned


    Dec 6, 2007
    +1 to the above. However class D amps can generally output square wave at their rated output, much like the SVT, however they will not sound like a slammed SVT. Class D amps are 'honest', and will faithfully reproduce the signal fed them, but if the signal only has a limiter on it, it will sound choked when you're slamming it. All well-designed tube amps are not honest, but they're engineered so they just sound better until you run out of power, then you just need more of them. There's lots of solid state amps like this too, like the old Traynor Mono Blocks. The 300W Mono Block II keeps up with an SVT no problem, and frankly the tone is different but on par.

    But really the biggest liars are the speaker cabs. It's one thing to know what your amp will put out, but what a bass speaker can take is another animal, and how efficient they are about doing it is another animal again. What good is a 600W bass cab when it's 1/4 as efficient as a 200W cab? The Eminence Delta Pro 15A in a vented bass cab can only handle 200W max or the cone slams into the magnet assembly, but at [email protected] it will kick the crap out of any cheap 600W (insert crap brands here) cab.

    This is why I rock a 700W [email protected] SWR G3 4x10 up on a stool or table. It has more output than an 800W [email protected] Ampeg 8x10, and focuses the sound where I need it instead of at my ass, knees, and ankles.
  12. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    The biggest lie is that watts are an important number for output.
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    +1. Driving a speaker to full displacement limited output requires a minimum voltage swing, not an ephemeral power rating. In the ranks of pro-sound we know the displacement limited voltage swing of our cabs and choose our amps accordingly. We have to, because the only way to restrict the amp output to make it impossible to blow drivers is with a limiter, and they're calibrated to limit voltage swing.
  14. seamonkey


    Aug 6, 2004
    You should also factor in Power Factor Correction (PFC). In non-US countries it's becoming standard that anything drawing high current needs PFC. Factories the use a lot of power know about PFC and add it in to save $$$ on power bills. Wikipedia has explanation, and Powersoft for audio amps.

    QSC is one of the most honest companies in providing "real" specs. And yes they have some amps with PFC.

    PFC is important enough that even your cell phone has it.

    The good news is all the Big Power Amplifier companies are only researching and designing PWM "Class-D" amplifiers, SMPS with PFC. It lets things get small light, Reliable, cheap, and best power in to power out over anything else.

    Check out some reasearch on PFC in large fluorescent light fixtures verses CFL light bulbs. Ooops - CFLs do save power but not as much as they could.
  15. seamonkey


    Aug 6, 2004
    Oh I don't know. And it's only published as 300W. We know a standard outlet can do 600W draw to power one.

    Sure would like to see some actual published measurements on one of these amps. Including power in from the wall to power out. They aren't really in competition with modern application so I doubt I ever will.
  16. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    One issue with non-PFC is that the lousy "power factor" of a standard capacitor and rectifier supply such as used by BOTH "heavy iron" AND SMPS amplifiers severely limits the amount of power that can be drawn from the wall..... you have a CURRENT limit, 15 or 20 A in the US, but a crummy power factor means that the current x voltage does NOT work out to equal the "actual/factual" power.

    normally, the 120V x 20A = 2400W is true but irrelevant.... because at a 0.6 power factor, you can only draw 0.6 x 2400W of "power", the rest is lost by drawing the current at the wrong "phase angle".

    Using a PFC, at the cost of "some" added power loss, will allow drawing more "actual" power from the outlet, since most of them will draw power at an almost 1.0 power factor, which means current x voltage DOES equal power.

    The SVT-8PRO is one amp that in the original version used a PFC, and I assume it still does.

    Further to the "real" vs "fake' power rating..... we rated it at 2500W, but we also put in a "time-power" limiter, that would not allow you to overload the outlet for very long..... it has a delay that lowers the allowed power at a rate depending on how far over the threshold you are, for how long. More time, or more power (or both) makes it limit faster.

    Upshot is that the amp produces the power for "long enough", but intentionally limits the long term power to approximately the capability of the outlet. I don't suppose that would be labeled "A fake power rating", but you never know.....
  17. +1. agedhorse post rock. :cool:
  18. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    That isn't the issue....... The issue is if the AMP can actually put out the power without overheating..... etc..... That has not much to do with the outlet, but is equally a sore point for the "fake rating" crowd.

    While I agree that it doesn't matter, and that most amps of more than a few hundred watts can NOT put out max power without overheating (and that includes many class-D + SMPS), it is interesting to see that a few some can..... even though it is not remotely needed.

    More than 1800W? Yep, how long you want it? The breaker has a curve of allowed current vs time, and you can get anything you want so long as you stay inside that. It's more than you may think.....

    But, in reality, you are not ALLOWED to draw more than 80% of the breaker rating for a "long term load", according to the national electrical code. Which is 12A for a 15A breaker, and 16A for a 20A breaker. Long term was not really defined for quite a while, but was generally accepted to be "over an hour" etc..... Now it is 3 hours.
  19. jeff7bass


    Apr 9, 2009
    I have all the Bass Gear magazines and they do test the true output power @ 8, 4, and even 2 ohms (when applicable). They suggested that very high powered amps may be more affected by un-regulated power sources however than lesser-powered amps. Not much though.
    It might be putting out 1375w instead of 1500w IF the voltage of the source is slightly less than it should be. When you’re talking about that much power, the effect is negligible (IMO). They used the Carvin B1500 head as an example.
  20. nysbob


    Sep 14, 2003
    Cincinnati OH
    The old RMS ratings meant something. Since those went bye bye, I don't pay any attention to power ratings. :help:
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    Oct 24, 2021

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.