50-75' Signal or Speaker Cables?

[Paul O]

That makes two of us - If it's powered off a 120V 20A circuit.

Why? That's no great feat even from a 15A circuit.

[Sydney]

Law of Conservation of Energy
The mains establish the power limit ( 2400 watts RMS on a 120V 20A circuit )
http://www.allaboutcircuits.com/vol_3/chpt_1/3.html
http://openbookproject.net/electricC...mi/SEMI_1.html
http://www.soundandcommunications.co...6_06_audio.htm

[billfitzmaurice]

I can't believe Peavey is getting 3000 watts

Neither would Einstein.

[AMC]

Law of Conservation of Energy
The mains establish the power limit ( 2400 watts RMS on a 120V 20A circuit )

And even that is optimistic. The average outlet is not 120V, and if your running long lines to your amp, even less. And keep in mind, that 2400 watt limit would assume 100% efficiency from the amp, and that you are using nothing else on that circuit (ie each amp in to a independent circuit) How often does that happen?

[Sydney]

The average outlet is not 120V,

Because of my location the line voltage is boosted. I've read over 125V - which can create other problems with legacy devices built when 115V was typical.
But yeah - the irrelevant power ratings are for advertising.
Bill Fitzmaurice pointed out ( on his forum ) a common but overlooked disclaimer that amps manufacturers use:
1/3 power represents program material with extremely heavy clipping.'

[AMC]

Because of my location the line voltage is boosted. I've read over 125V - which can create other problems with legacy devices built when 115V was typical.
But yeah - the irrelevant power ratings are for advertising.
Bill Fitzmaurice pointed out ( on his forum ) a common but overlooked disclaimer that amps manufacturers use:
1/3 power represents program material with extremely heavy clipping.'

In the end, if the amp does what you want, it's powerful enough, if it doesn't, it's not. Ratings be damned.

Car audio used to do this sort of thing also, rating their amps with a 14 or 15 volt input.

[Paul O]

Law of Conservation of Energy

I'm not disputing those accepted standards, you guy are simply missing or ignoring the fact that music is NOT a 60hz sinewave it's actually a complex AC waveform with sometimes tremendous dynamic range, so AC wall power simply does not transfer at a maximum 1:1 ratio into audio power and it is entirely possible to get more "audio watts" out of an amp than it consumes in AC watts at the wall socket. If the standard for measuring an amplifiers output power was a 60hz sinewave then I'd agree with you 100%, but the reality is that isn't the case and there are many different ways to measure it that while technically valid range from reasonable to smoked-your-lunch fantasy.

http://www.peavey.com/support/techno.../chapter_4.pdf

[Sydney]

and it is entirely possible to get more "watts" out of an amp than it consumes at the wall socket.

That's not possible.

[billfitzmaurice]

it is entirely possible to get more "audio watts" out of an amp than it consumes in AC watts at the wall socket.

Not continuous, and that's what I'm concerned with, not what an amp can produce for a few minutes before it goes into thermal shutdown.

In the end, if the amp does what you want, it's powerful enough, if it doesn't, it's not. Ratings be damned.

When I pay for something I expect to receive exactly what I paid for. If you don't care if you're hornswoggled that's your business.

[Sydney]

Peavey is clouding the issue with references to STORAGE. A capacitor stores but doesn't create energy nor does it work at 100% efficiency. Capacitors store during 1/2 of their duty cycle and discharge during the other half. The duty cycle is determined on line frequency 60hz = 1/60 of a second or almost 17ms.
I do understand the composition and dynamics of music ( I did a college paper in the 70's on Fourier Analysis and Wave synthesis ) The "extra energy" provided is irrelevant as music notes can also be sustained for much longer than the capacitor drain off.
The 1/3 duty cycle burst tests are also unlike music and bear no resemblance to real use and the tests certainly carry enough disclosures and disclaimers to show their lack of significance.
This is a weak attempt by Peavey to justify a misleading practice.

[Paul O]

Peavey is clouding the issue with references to STORAGE. This is a weak attempt by Peavey to justify a misleading practice.

Yes and no, the article doesn't offer much to support the claim, but manufacturers have long since abandoned the idea of building amplifiers that can sustain a continuous sine wave at rated power for any meaningfull amount of time.. since music has little relation to that signal anyway, so numbers presented with that basis have to be taken with the knowledge that it doesn't tell you the whole story.. just like any other spec you want to consider. Yes a sine wave test is a valid way of measuring an amplifier, but so is a pink noise test, a burst test, or a sweep test, they all give you different results but none of them is any more meaningfull or meaningless than the other.

[Sydney]

The Peavey article offers nothing in the way of technical reference, qualification and quantification.
The inference that it's too complex a subject for most engineers to understand is unsupportable.
It doesn't matter if a music signal is a sine wave/ or a square wave from Moog or a sustained guitar note - If the amp can't sustain the level for as long as necessary.
It is what is continuous and sustainable long term that is relevant AT full spectrum and low distortion. Frequency limited bursts of heavy clipped signal is not.

[AMC]

When I pay for something I expect to receive exactly what I paid for. If you don't care if you're hornswoggled that's your business.

I learned long ago not to trust ratings. Performance is all that matters.

[Sydney]

I learned long ago not to trust ratings. Performance is all that matters.

Ratings have to have merit and qualification.
Like other advertised products: companies want to sell perceptions.
Automobiles are advertised in a fantasy light doing stunts that are physically impossible, impractical and unrealistic, with a small type disclaimer.
Big watt numbers sell units, consumer electronics manufacturers have know this for a long time. ( See the link I posted on testing ).
If I advertised that a vehicle gets incredible gas mileage and increased speed ( * All measurements made going downhill ), the irrelevance would be obvious.
It's weird that the analogy of a toilet was used to represent capacitor discharge.
The analogy I ( perhaps thousands of others ) were given as a student was this:



This is far more apt

[AMC]

Ratings have to have merit and qualification.

In an ideal world. I've seen rating that matter, and I've seen them fudged to the point of absurdity. Until the audio industry is willing to establish (re-establish) true parameters for ratings, it's all a crap shoot. That's where following trusted brands and honest retailers comes in. I guess in my old age I've just become jaded, and for that I blame an industry that seems to at best accept, and at worst promote, unscrupulous behaviour.

[Sydney]

In an ideal world. I've seen rating that matter, and I've seen them fudged to the point of absurdity.

Believe me I have too...
My father's job ( product safety engineer ), often involved performance measurements on his company's products, and that of other companies.
He related the "tricks" that are used to make fudge.

[wg_ski]

Not continuous, and that's what I'm concerned with, not what an amp can produce for a few minutes before it goes into thermal shutdown.
When I pay for something I expect to receive exactly what I paid for. If you don't care if you're hornswoggled that's your business.

Can you even buy an amplifier that can put out full sine wave power out indefinitely? I don't even think there's one on the market that can. And even if it did, you couldn't legally run it off a standard Edison plug - even the 20 amp variety. There were a few - and only a few - mostly the heavy iron Crests and Crowns of yesteryear. And they had 30 amp plugs. I don't think the modern stuff can do more than 1/3 power - and certainly none of the switchmode amps can. The non-touring-grade units - which is the majority of what is out there - are only good for 1/8 power. And are only expected to last about a year doing it. The cheap cheap cheap amps like Pyle can't even do that of course. What they put into a powered speaker is likely to be just the minimum they can get by with and not have every one of them come back under warranty.

What would you end up paying for an amp that really could do 2000 watts full sine wave indefinitely, anyway? $10k, perhaps?

[Sydney]

Can you even buy an amplifier that can put out full sine wave power out indefinitely?

That all depends on at what power level and what level of waveform degradation is acceptable.
In essence a device that puts out a sine wave ( or any waveform ) continuously is an oscillator.

[wg_ski]

That all depends on at what power level and what level of waveform degradation is acceptable.

At the maximum signal level possible, just at the onset of clipping, of course. Any amplifier can put out a sine wave forever if you back it off far enough. What's missing are ones that can do so at full rail to rail output with a 4 ohm load. Whether that capability is needed is certainly in debate. What is very clear is that amps have been getting progressively less expensive "per watt" over the years, and it seems to be directly correlated to the liberites the manufacturers take with the specs.

In essence a device that puts out a sine wave ( or any waveform ) continuously is an oscillator.

Only if it does so without a signal input.

[Sydney]

Only if it does so without a signal input.

That's not true. Oscillators are the basis of Fourier synthesis in a Moog for instance or a radio or a variety of other circuits and one of the first circuits given to students because it involves resonance. Their amplitude is often control by voltage as in VCO. And they can be modulated
Note that the better amps include the frequency spectrum ( bandwidth ) and the amount of degradation at a specific amount of gain in db's.
One example stated that the gain is to be set to 32db, exceed this and the performance degrades.