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Tech experts: Is Boss lying to us about amp watts?

Stu Blue

Member
Messages
3,167
Tech experts only please ..... Boss fans boys not wanted here.

Boss claim the Wazza amp is 150watts but it only consumes 110watts. Likewise the Katana 100 is supposed to output 100watts but only consumes 72 watts. Is that possible with class D or whatever?

My Marshall JTM45 consumes 160watts for 30watts out, while I seem to remember an SS amp consuming twice the watts it output.

Surely an amp which outputs more power than it consumes is some sort of perpetual motion machine... where are the extra 28 watts coming from? Amplifiers use the power they consume from the mains to amplify the input signal. I don't see how an amp can output more power(watts) than it consumes.

Are Boss lying their way back to the bad old days before the RMS standard with stuff like "Music Power"... as a kid I remember seeing a 2x6v6 amp advertised as 100 watts "Music Power" (in real world RMS only 20watts)....
 
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tenchijin2

Member
Messages
3,030
http://tjcornish.com/articles/understanding-power-consump.html
Keeping in mind that we are powering this amplifier from a 20A 120V circuit capable of 2400W of sustained power delivery, it is interesting to see that the amplifier’s claimed power output values are significantly higher than the input power available to the amp – 8000 watts of power output with 2400 watts of input. This is possible because of the intermittent nature of audio signals. Two mechanisms enable this: circuit breakers typically allow more current – possibly several times more than the rating – for brief periods of time, and the amplifier has a capacitor bank that stores energy when demand is low, to meet peak demand.
This should apply to what you're seeing.
 

darkfenriz

Member
Messages
206
A very typical approach of big manufacturers is to state the theoretical power of the power module @4ohms while they put inside the 8ohms speaker.
Nearly twofold inlation of the watts number while technically not lying. (hey, there's even an exteral speaker jack that you'll never use).

Still, most solid state amps will not be able to deliver anywhere near the stated power for a prolonged period due to thermal limitations and unsuitable heatsinks. The culprit is the idea borrowed from hi-fi that the mean power is way below power peaks, but this does not apply to all-the-time-clipping-happy guitar.
 

Stu Blue

Member
Messages
3,167
What amplifier manufacturer anywhere ever told the truth about wattage?
When I've seen them tested on a bench with a scope etc.... Quad, Fender, Marshall...... even an HH solid state amp I briefly had in the 70s (50watts into 16ohms, 100watts into 8ohms, 200 into 4ohms just as claimed. Mind you it cost as much as a Marshall JMP SL100 at the time so that's what i swapped it for).......
 

Tone_Terrific

Silver Supporting Member
Messages
34,486
When I've seen them tested on a bench with a scope etc.... Quad, Fender, Marshall...... even an HH solid state amp I briefly had in the 70s (50watts into 16ohms, 100watts into 8ohms, 200 into 4ohms just as claimed. Mind you it cost as much as a Marshall JMP SL100 at the time so that's what i swapped it for).......
They were good.
I had an L6 Duoverb (stereo power out) that delivered an honest measurable 50w/side, just as claimed.
Wazza amp is 150watts but it only consumes 110watts.
110W idling, average, or at full output?
 

Stu Blue

Member
Messages
3,167
110W idling, average, or at full output?
Good question.. I always just assumed the figure printed of the back of amps was the maximum so that folk didn't use unsuitable wire/power supply/fuse etc. I can't see what the point of printing a lower figure would be (ie: Idling). (My electric cooker has the max possible figure printed BTW). I'm fairly sure stating the max possible power demand is part of the legal regulations for selling any electrical goods in Europe.....
 

Tone_Terrific

Silver Supporting Member
Messages
34,486
I'm fairly sure stating the max possible power demand is part of the legal regulations for selling any electrical goods in Europe.....
One would assume so.
Any tech should be able to confirm the power output of the Boss stuff within a few minutes.
If I had any I'd let you know.
That said, if it's loud enough the numbers matter little.
 

MKB

Silver Supporting Member
Messages
8,658
The RMS standard is a constant sine wave, no breaks or low demand moments for caps to recharge... surely that is the BS Peak Music Power rating.
Back in the early days of solid state IIRC the power ratings were all over the place (instantaneous peak power, RMS, sine wave, etc). At one time there was a federal requirement that you had to measure the power of your amp according to a certain standard (Watts RMS continuous with a 1kHz sine wave into a specified load). It looks like that requirement may no longer be in effect, or it is getting ignored. Not necessarily a good thing.

If Boss rates the amp at an output power rating lower than the power consumption, they must not be rating it in continuous RMS watts. So there is probably a bit of specsmanship going on. Although to be fair some of your speakers may not be rated for continuous RMS power either.
 

mark123

Member
Messages
1,062
Just looked at the back of my trusty old solid state Peavey Stereo Chorus 2x12 for grins. A pretty honest 130 watts rms per channel stereo, one of my favorite clean amps and heavy as hell. Also pulls 600 watts at 120v!
 

TimmyP

Member
Messages
2,488
What is common, at least with Class D and similar, when stating the power, is neglecting to state the time duration of said power rating. An amp may put out 1kW sine wave for 1 second, at which time the power may cut a significant percentage. If the signal continues, the signal may step down a few more times before reaching a level that it can sustain 'forever'. With some amps, this may be only 25% of the rated power.
 

J M Fahey

Member
Messages
2,934
Boss claim the Wazza amp is 150watts but it only consumes 110watts. Likewise the Katana 100 is supposed to output 100watts but only consumes 72 watts. Is that possible with class D or whatever?

Surely an amp which outputs more power than it consumes is some sort of perpetual motion machine... where are the extra 28 watts coming from? Amplifiers use the power they consume from the mains to amplify the input signal. I don't see how an amp can output more power(watts) than it consumes.
Don´t think they imply Energy generation out of nothing :)
We need a little more data, I hate giving "blanket" answers .

1) what else is stated together with "150W" .... RMS/Peak/Music/PMPO/EIA/EIAJ/... ???

2) watts/V.A. indication printed right beside the power cable *used* to be constant or average or maximum mains power consumption, mainly to help you select cables/extensions/even autotransformer if used overseas ... so it was realistic, and often inflated for safety reasons.

I remember 100W Plexis, which actually need about 380W (V.A. really) being suggested to be paired with 500W autotransformers ... and it was *good* advice, for safety and better performance.

But nowadays users are "Green minded" and reject perceived high consumption or inefficient stuff, so sadly the pendulum has swung fully to the other side, and often manufacturers print the "idle" consumption (I have seen verified 100/150W RMS Home Theaters and such labelled "20W" .... which is what they use if left plugged in but not played, or best case used playing average level music (or watching a movie) in an appartment living room ... usually no more than 10/15% max output power, if that much.

So for a more precise answer please link the user manual. :)
 

easyed

Senior Member
Messages
2,561
Back in the early days of solid state IIRC the power ratings were all over the place C, RMS, sine wave, etc). At one time there was a federal requirement that you had to measure the power of your amp according to a certain standard (Watts RMS continuous with a 1kHz sine wave into a specified load). It looks like that requirement may no longer be in effect, or it is getting ignored. Not necessarily a good thing.
I shopped for SS stereo amps, etc, in the "early days" and saw very few SS amps rated for RMS output. The Institute of High Fidelity had one rating system that was somewhat more optimistic than RMS. Lafayette, Radio Shack, and other retail sellers sold amps rated IPP (instantaneous peak power), that I took to mean a millisecond before the amp blew. I called IPP "When I pi$$ purple" and figured the real RMS power was about 1/3 of the IPP, but it really didn't matter, since I was only running in a dorm room.

I find that the labeling of the backs of amps can be questionable (to be kind). The rating of the primary power fuse x the wall voltage will give you a better idea of max power consumption.
 

diagrammatiks

Member
Messages
3,024
1. there is really no standard for guitar amp wattage claims. HIFI is a little bit better but not by much.

2. class D can be very efficient, but it really depends on how they are labeling the input/output wattage.
tube amps are very very inefficient so they will draw much more power then they put out.
 

musekatcher

Member
Messages
2,735
Tech experts only please ..... Boss fans boys not wanted here.

Boss claim the Wazza amp is 150watts but it only consumes 110watts. Likewise the Katana 100 is supposed to output 100watts but only consumes 72 watts. Is that possible with class D or whatever?
Peak vs continuous. Your faucet delivers 1 quart a minute continuous. That's 1 quart a minute down the drain. If you catch 2 minutes worth in a pan, you've stored 2 quarts in the pan. You dump the pan, and now deliver 2 quarts that takes a minute to drain, so you created 2 quarts per minute, but only for that 1 minute, afterwhich it goes back to the 1 quart a minute. 1 qt per min continuous, 2 qts peak. Same with an amp, a motor - anything that delivers power. That device also stores power. 100W continuous, 200W peak is typical. Music instrument amplifier consumers seem to be less interested in precise ratings and standards btw.
 

Tone_Terrific

Silver Supporting Member
Messages
34,486
Music instrument amplifier consumers seem to be less interested in precise ratings and standards btw.
The question is what does it actually put out as measured by conventional means i.e. continuous, sine wave, AC RMS.
The stated output looks like hype.
Is that unethical on the part of Boss?
Well, it's certainly not illegal or unordinary.
 






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