Is there an Electrical Engineer in the house?

Gas Hed

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1,250
Or at least someone that understands Watts? I just picked up a Headrush FRFR for my acoustic guitar rig and it's got this great promo sticker on it saying 2000 WATTS. What does that really mean? Especially considering it doesn't get nearly as loud as my 15 Watt tube amp?
 

VICOwner

Gold Supporting Member
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2,449
I’m not an electrical engineer. I do build amps and have a decent electrical background. Here’s a formula you can take to the bank on electrical power. Volts X amps = wattage. If you figure that the fuse rating is the most current that the amp can “move” through it’s chassis times the input voltage, this is the maximum “power” that can be dissipated. 2000 watts @ 120 volts is 16.66 amps of current. Amplifiers waste some input power producing output power. Tube amplifiers waste quite a bit more power than solid state amplifiers because of the heater circuit used to warm the cathodes but all amplifiers require more input power than they can output. Most common household circuits are protected by a 15-20 amp circuit breaker and they rarely feed a single receptacle. I will take a chance and say the amp is more likely to output more like 200 watts at best for any real amount of time. It’s internal filter capacitors have a storage capacity that can be depleted quickly and therefore an output surge can occur but this happens very quickly and although it’s possible to get some ridiculous current levels for just a millisecond but it’s not sustainable.
 

mikekim

Member
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724
The Headrush series will apparently handle 2000w Peak (combined High (1300w) and Low (700w) Frequencies)

Headrush Specification Sheet

I reality they're more like 1000w but 2000w sounds much more impressive.
I have a pair of 108's and I've measured them at over 115db (which is loud enough to cause permanent hearing damage after 30 seconds of exposure :oops: )

Tube Vs Solid State wattage is a big grey area... as its not really output volume that is the main concern here (as doubling the power will only give you a +3db output) , but the amount of headroom available ( a higher wattage system will handle more load before clipping)
 

jvin248

Member
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6,923
.

Your question is really trying to translate Watts into Loudness.

More of a question: What are the speakers and how much air are they moving?

Example ... "How to make a small solid state practice amp sound like a Monster":







There are some old threads suggesting that tube amp builders use a different method of calculating Watts than solid state amp builders. That a 5W tube amp is much much louder than a 5W solid state amp. True or wishful Marketing? So there is that too.


.
 
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Bob Pollock

Altes Holz
Gold Supporting Member
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5,930
Or at least someone that understands Watts? I just picked up a Headrush FRFR for my acoustic guitar rig and it's got this great promo sticker on it saying 2000 WATTS. What does that really mean? Especially considering it doesn't get nearly as loud as my 15 Watt tube amp?
The Headrush FRFR108 can get very loud, but it needs a preamp. It won't be very loud if you're plugging your guitar in directly.
 

MikeMcK

Gold Supporting Member
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6,529
I haven't worked as an engineer in many years, but that also means I've been around long enough to have seen a lot of creative power ratings.

One reason there's so much leeway in claiming a specific power rating is that there different ways to measure signals. As @VICOwner pointed out, P (power in Watts) = V (voltage, in Volts, duh) x I (current, in Amperes). But there are different ways to calculate voltage.

For practical purposes, the most meaningful way to measure voltage of an amplified signal to pick some maximum allowable distortion value and find the maximum RMS voltage that can be achieved within that rating. But that's not what people do when they need the largest possible value for marketing purposes. Using peak-to-peak voltage in the calculation is less meaningful, but yields a bigger number.

Then there's the matter of what kind of signal is used. A sine wave may be the most meaningful, but then the question is, "at what frequency?" And for audio, there's the matter of asking, "and what is that maximum allowable distortion at which we can say we have a valid measurement?"

It's obvious that guitar amps aren't supposed to be ultra-linear clean amplifiers, so it might be valid to pick a relatively high amount of allowable distortion (and remember, "distortion" here technically means any change in the signal shape, not just what we guitarists get from a distortion pedal).

It's less obvious that consumers prefer a certain amount of distortion in most audio equipment. Remember what happened in the '60's, when the miracle of cheap transistors finally let audio companies build the super-clean hi-fi equipment audiophiles said they wanted. They did, and then audiophiles said, "nah, that sounds sterile. I'll keep using my McIntosh tube amp."

For awhile it seemed like some audio equipment makers had come to a kind of truce where they settled in on reasonable RMS power ratings that made some kind of sense, but in the past few years it looks like we're back to the point where makers just use the largest number they can get away with putting in the ad.

Sorry if that doesn't help in trying to compare gear, but that's where we are.
 

jdh

Silver Supporting Member
Messages
239
Let's first be specific about the actual electrical power the unit can output. The amp has a 10 amp/120 volt fuse which will properly be derated to 7.5 amps. Maximum available output power is 120 x 7.5 = 900 wats rms. Peak power is 900 x 1.414 = 1272.6 watts. This would be at 100% efficiency, but the amp is perhaps 85% efficiency: 765 rms/ 1082 peak watts. One must further consider the efficiency of the loudspeakers and their enclosure as they will also output some amount less than they input. Whoa, a lot of variables here!

To further clarify, amplifiers cannot output more power than they input. The only thing close to this is the TOKAMAC fusion reactor or the Lawrence Livermore/National Ignition Facility laser-fired fusion reactor. Even these are not 100% efficient at this point in time, and they only run for a few minutes. If you think a handwired boutique amp is expensive you should dig the price tag on these monstrosities.
 
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Jim Hagerman

Vendor
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343
Yes, they do say "peak power" on their website. Clearly it has a class D type amplifier inside, which can be very efficient. By "peak" they probably mean a single unsustained impulse, not sinewave or squarewave. Marketing BS.
Also, since you were looking for an EE, I would like to muddy up the waters a bit noting you also have to take the phase angle difference between voltage and current! Out-of-phase reactive power can end up drawing much higher currents (inductive or capacitive load). This is why transformers are rated in VA (volt-amps) and not watts.
 

SgtThump

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8,176
Im under the impression that everyone on TGP is an electrical engineer? ;)
 
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teemuk

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3,671
By "peak" they probably mean a single unsustained impulse, not sinewave or squarewave.

Since that monitor is compact enough to look like a class-D amp they most definitely are not quoting a continuous rating. Class-D amps are generally not designed for that. Then again, in practice we do not feed our amps continuous sine or square waves so those burst power ratings will cover usual music (instrument) signals just fine.

Marketing BS.
Marketing is nearly always that. Best practice is to learn what those ratings mean so marketing can no longer fool you.

For instance, output power DOES NOT mean how loud the amplifier is. It's just amount of power the amplifier can produce. In audio amplification this power drives a transducer, a loudspeaker, which is what produces the sound pressure changes and in the end defines how loud things can be. Some speakers are louder than others.

Power we can use as a rough estimation of how much sound pressure a specific transducer generates with x amount of power fed into it - that is, once we know the specs of that transducer. The relation is, however, logarithmic so in order to produce just a slightly louder signal we need roughly two times more output power. For getting twice as loud we need roughly ten times more output power, and for getting ten times louder we need about hundred times more output power. So, amps with high power ratings are not significantly louder than amps with low power ratings to begin with, and differences in output power ratings may be swamped by differences in transducer efficiency.

There are also several psychoacoustic effects that explain why a distorted and mid-range focused signal from a low power amp (e.g. overdriven tube guitar amp) can easily seem louder than a non-distorted full range audio signal from a high power amp (e.g. PA or bass amp).
 

MikeMcK

Gold Supporting Member
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6,529
Im under the impression that everyone on TGP is an electrical engineer? ;)
LOL, not everyone, but probably a lot. I remember an undergrad prof who observed that his generation of EE students were mostly people who had ham radio licenses, but our generation seemed to all be musicians.

Makes sense... there's a proven high correlation between math ability and studying music.
 

Sushi Box FX

Silver Supporting Member
Messages
352
LOL, not everyone, but probably a lot. I remember an undergrad prof who observed that his generation of EE students were mostly people who had ham radio licenses, but our generation seemed to all be musicians.
I was disappointed that I was the only musician in my EE classes. There was actually one HAM operator, he was cool. My school pushed SW/FW and VLSI hard in the EE curriculum though, so most of the EE students either wanted to code or work in semiconductors. Bunch of weirdos.

Oh and one girl was getting an EE degree as a precursor to law school, with the intent to be a patent lawyer. She makes a $hitload of money now.
 
Messages
1,346
Or at least someone that understands Watts? I just picked up a Headrush FRFR for my acoustic guitar rig and it's got this great promo sticker on it saying 2000 WATTS. What does that really mean? Especially considering it doesn't get nearly as loud as my 15 Watt tube amp?
I only minored in EE over a decade ago, but...

Watts is a measurement of maximum electical power. Watts is really only important when you are matching amplifiers to speakers (or if you are trying to determine if you want to foolishly grab a live wire with your hand). Watts has a weak correlation to decibles (which is the actual measurement of volume). So if you use watts to determine how loud something will be, you will most likely be disappointed. There are plenty examples of 30W amps being louder than 100W amps.
 

Tone_Terrific

Silver Supporting Member
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36,521
Plug in.
Drive it into as much distortion as you can handle and that is how loud your system can be...if nothing blows up.
Watt ratings on many current SS amps are misleading to outright bogus.
2000W used to fill a concert hall.
 

Quad4

Member
Messages
1,698
This comes down to:
  • Marketing
  • How they measure watts ( RMS, Peak, etc.)
  • Ability to handle transients
  • How they distort when pushed hard. Does it sound musical or like crap. Tube sound great as they distort, but Class D amps.....
 

teemuk

Member
Messages
3,671
With output power figures in the kilowatt region I don't think the main intention is that people crank these things into clipping distortion. More likely ensuring clean reproduction of transients even at fairly high levels of loudness.

Niceness of class-D -based amp distortion is amp-specific (similarly to tube amp distortion) in practice ranging from tube emulations of guitar amps to downright horrible performance of vintage class-D designs. In practice most modern class-D amps are designed to handle clipping and overdrive well. I also expect that a monitor speaker such as this likely engages some sort limiters in case of clipping.
 




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