• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Amplifier Wattage

Status
Not open for further replies.

audioguru

Well-Known Member
Most Helpful Member
Many amplifier manufacturers lie about the power of their amplifiers. I call it Whats insted of Watts:
1) Peak Power or Maximum power is simply double the real amount of power.
2) 10% distortion instead of barely at clipping with very low distortion.
3) At only 1kHz instead of from 20Hz to 20kHz.
4) "Music Power" which is only for a moment before the power supply voltage sags.

I worked for a PRO audio products company. Our best amplifier was very powerful and was indestructable.
I tested a competitor's amplifier and it quickly smoked.

Power Test:
1) Make sure the mains voltage is what it is supposed to be.
2) Load the amplifier with its rated load resistance with a non-inductive resistor.
3) Feed it a sine-wave from 20Hz to 20kHz and see its waveform on an oscilloscope. 4) Turn up the level until you see the waveform clip.
5) Measure the voltage and calculate the power.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Power Test:
1) Make sure the mains voltage is what it is supposed to be.
2) Load the amplifier with its rated load resistance with a non-inductive resistor.
3) Feed it a sine-wave from 20Hz to 20kHz and see its waveform on an oscilloscope. 4) Turn up the level until you see the waveform clip.
5) Measure the voltage and calculate the power.
6) Put out the burning amplifier with a fire extinguisher.

7) Throw in the bin.


It needs to be a pretty decent amplifier to withstand full power sinewave testing like that, a cheap one will probably self-destruct.

AG is a little pessimistic about amplifier powers, any decent quality amplifier will quote RMS continuous power at a specified distortion, at a specified frequency or frequency range. Generally all PA amplifiers will do so, as they are commonly run at or near (or above) their specifications - and making exaggerated claims about their power will quickly destroy them.

The worst culprits are in-car amplifiers, where's it's common to claim an amplifier is 1000W when it might only be 50W (if that).

There's been a recent thread about a guy who bought some chinese amplifiers, they said "180W + 180W" on them, yet only used two 8W amplifiers, and didn't work for more than a few minutes.
 

Sceadwian

Banned
They've cracked down on that stuff a little bit in the US. It's now required that if you have a power rating on the box that RMS be listed and the testing methods are standardized. This has been largely bypassed by simply no longer putting the power ratings on the box of cheap equipment. They made the law primarily for car audio shops because as Nigel said they were simply lying through their teeth about the real performance of the systems they were selling.
 

Thunderchild

New Member
I just loved the PMPO of computer speakers (incorporating amps) and nearly burst out laughing when retailers and school mate boasted about their out put power. one guy just wouldn't get it even when i told him: "look theres not even room in there for a 100 W power supply let alone a 100 W amp and speakers" that still didn't comvince....

of course i took my first pair on 240 W PMPO apart to find a 4 W speaker in each (and suspect the am was more like 2 W)

people just don't seem to understand just how powerful 5 W RMS is
 

Sceadwian

Banned
I do my homework on speakers for my computer. I used to have a really nice 5.1 system that was only about 200 watts total between the satellites and the sub and I could piss the neighbors off with it easy. I miss that setup. I'm stuck with a pair of 4 watt desktop one's now which are more than loud enough, but each speaker only has a pair of 1 inch drivers in it, the enclosure's are ported but the frequency response still sucks. No mids and weak bass.
 

audioguru

Well-Known Member
Most Helpful Member
Many years ago in their catalog Sears had a disclaimer in small writing about their "240W" stereo console:
"Our 240W stereo console actually produces 4W RMS per channel continuously from 20Hz to 20kHz at low distortion."
 

Sceadwian

Banned
Buncha frauds taking advantage of the technically illiterate! Crap like that is half the reason I started learning about electronics in the first place. I would see the prices on some stuff and with what little I knew then think "It can't really cost THAT much"

With companies out there making monoblock amplifiers and selling them for 1000% markup or worse =O it just really ticks me off. Or things like "Monster Cables" Which are completely pointless. Just as an example. Radioshack sells a "Monster cable" For component video that costs 130 dollars! I use RCA audio cable from my DVD component out to the TV, and the picture is fantastic =\ The cables I'm using came free with my last set of speakers...
 
Last edited:

Sceadwian

Banned
Litz wire you mean? That is supposed to be good but only for high power audio over longer runs. Has to do with the 'skin effect' of 'normal' wire.
Gold actually is a good idea for connectors. If both connector and receptacle are gold plated they have a tendency to bond to each other. That and golds general good electrical conductance and high chemical resistance makes it an almost ideal choice for connectors.
 
Last edited:

tcmtech

Banned
Most Helpful Member
I used to do custom audio work in high school and college years ago.

I entered a local crank it up contest and got booted for running modified equipment in the modified and unlimited class. There sound measuring devices said I had far more power than what my amp specs said I should have. Plus they were the ones that pointed out most of what You read below!

I sat in the parking lot with my windows down and walked all over several of the high end cars with name brand everything and crappy actual sound quality.
I had people ask me why I was not competing? They said my sound quality was very nice. Well balanced smooth and rich yet loud at the same time. The pro cars were loud but distorted and just not that pleasing to the ear.

I told them they booted me from the unlimited and modified class for knowing how physics works! It went agianst their rules. Plus I didnt have my car covered in peel and stick "steal my stuff" stickers.

I had many "experts" tell me running my amps with zero gauge welder cable for the power supply end will burn them out because its not fine enough stranded cable or because its not properly polarized!

And that running my free air rated subs free air will make them fall apart? plus the size of the box does not determine a subwoofers acoustical resonant frequency, the wattage of the amplifier does. Free air uses the whole trunk for the box.

And that running 12 gauge speaker cable from my amps (18 inches away) will cause so much power loss the amps will overheat or burn out. Plus if its not properly polarized the electrons cant flow in the right direction and will back up and cause wire fires!

I had several "audio experts" tell me I need sound ramping devices so that if I turn it up all the way from dead off my speakers will fly apart Because they need to get moving gradualy.

Also I was told time and time again that an amplifier can only do what its rated for no matter how much you modify it. Raising the rail voltage 50% and changing the output devices to run at 6 times their factory designed current limits and modifying the feed back, protection circuitry, and power supply to handle that change wont do anything because that number on the case determines everything, The factory lable determines what its capable of not how its built or been rebuilt!

To bad I was only 19 at the time.
 

Thunderchild

New Member
If both connector and receptacle are gold plated they have a tendency to bond to each other. That and golds general good electrical conductance and high chemical resistance makes it an almost ideal choice for connectors.
yes but these connectors are often advertised as improving sound quality.....
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top