[dave_c]

http://www.expansionsolutions.com/media_center.htm

1000watt @ 8ohm amp built into a HTPC?  I dunno about that one. . .

[BradJudy]

More detailed specs:

7.1 audio output to deliver 125 watts@ 4 ohms into each of the front, center, and rear channels

· 250 watt@ 4 ohm output for a component subwoofer.

· Stable to 2 ohms.

· High current draw power supply capable of 1000W for 10 ms.

The total power at 4ohms is 1125W and the 1000W seems to be a peak value.  Definitely a jumble of specs.  

7x125W in a media PC isn't unrealistic with some of the amp modules out there (like the D2Audio one), so there is no reason to think it can't be done.

[avahifi]

Lets see, 125 watts into 4 ohms pulls about 5 amps of continuous current from the amplifier.  Times seven channels requires 35 amps of current.

Just wondering where all the current is coming from?  Not very likely from a standard 15 amp rated residental AC wall outlet for sure.

Possibly from smoke and mirrors?  Or am I overlooking something?

Frank Van Alstine

[Jimbobntnr]

(like the D2Audio one), ...

Bingo.

[speaker]

Lets see, 125 watts into 4 ohms pulls about 5 amps of continuous current from the amplifier.  Times seven channels requires 35 amps of current.

Just wondering where all the current is coming from?  Not very likely from a standard 15 amp rated residental AC wall outlet for sure.

Possibly from smoke and mirrors?  Or am I overlooking something?

Frank Van Alstine

Continuously?

Wouldn't that only happen if using sine waves as program material?

 

speaker

[avahifi]

Our Fet Valve 550EXR amp makes plus and minus 65 volts into 8 ohms continouosly.  We understate its power at more than 250 watts per channel RMS.

Lets see what we could have done using similar specifictions as we suspect was done with the digital amplifier mentioned above.

First we could have rated it at peak power rather that RMS, that brings it up to more than 525 watts per channel.  Then we could have translated the power into a 4 ohm rating, 1050 watts per channel (oh wow!!!).  Then we could have use the same logic Speaker suggests "Wouldn't that only happen if using sine waves as program material?" and put in a music power fudge factor, and at that point we are approaching 2000 watts per channel, then of course, sum the ratings of each independent channel to give you one big fat number.  The AVA Fet Valve 550EXR 4000 watt amplifier.  So there!

Step right up in line and buy your 4000 watt amplifier right here.

Get the picture?

Frank Van Alstine

[MaxCast]

It says the power supply is capable of 1000watts for 10ms.  Is that the same as power output?   And for 10 ms....that's like a spark isn't it?

[Bingenito]

Lets see, 125 watts into 4 ohms pulls about 5 amps of continuous current from the amplifier. Times seven channels requires 35 amps of current.

Just wondering where all the current is coming from? Not very likely from a standard 15 amp rated residental AC wall outlet for sure.

Possibly from smoke and mirrors? Or am I overlooking something?

Your posts always kill me, because you are always right and have a cynical tone to the response.
 
It also seems like people never want to here basic science (truth).

[BradJudy]

Lets see, 125 watts into 4 ohms pulls about 5 amps of continuous current from the amplifier.  Times seven channels requires 35 amps of current.

Just wondering where all the current is coming from?  Not very likely from a standard 15 amp rated residental AC wall outlet for sure.

Possibly from smoke and mirrors?  Or am I overlooking something?

Frank Van Alstine

This is true of MANY multichannel amps out there.  There are plenty of 5-7x200W@4ohm options out there that have a 15A inlet.  

Let's look at the max total power consumption on these amps.  How about an Aragon 2007 as an example. (This isn't meant to pick on Aragon, most high power multichannel amps are the same way.)  Rated at 7x300W@4ohm, it theoretically could eat a lot more current (not to mention the likely difference in effeciency as well).  But, it is spec'ed at a max power draw of 1200W which means it can't nearly put out the max rated power to all channels at once, but can safely live on a 15A circuit.  Multichannel amps aren't deisgned to put out their max rated power to all channels at the same time.

[Jimbobntnr]

To alleviate any 'mysterious' x factor on this product, it has a d2audio xrt 125 built in.

[speaker]

Our Fet Valve 550EXR amp makes plus and minus 65 volts into 8 ohms continouosly.  We understate its power at more than 250 watts per channel RMS.

Lets see what we could have done using similar specifictions as we suspect was done with the digital amplifier mentioned above.

First we could have rated it at peak power rather that RMS, that brings it up to more than 525 watts per channel.  Then we could have translated the power into a 4 ohm rating, 1050 watts per channel (oh wow!!!).  Then we could have  ...

When would one use "continuous" power?

When listening to music or when listening to a sine wave?

speaker

[speaker]

Lets see, 125 watts into 4 ohms pulls about 5 amps of continuous current from the amplifier.  Times seven channels requires 35 amps of current.

Just wondering where all the current is coming from?  Not very likely from a standard 15 amp rated residental AC wall outlet for sure.

Possibly from smoke and mirrors?  Or am I overlooking something?

Frank Van Alstine

A 15A/120VAC wall socket has an 1800W potential.

How are you arriving at 35A?

 

speaker

[YoungDave]

Frank VanA is right, of course - it is, most certainly, smoke and mirrors.  Power ratings are all about standards, measured under repeatable laboratory conditions, not (subjective & non-repeatable) listening conditions.

So, no, we don't listen to a 250W sine wave.  The point is, power ratings are measured with sine waves - and with both channels driven, and continuously.  Doesn't matter at all whether we listen like that: It's a STANDARD, get it?

So when a manufacturer like this Expansion-Solutions outfit phonies-up their power ratings by telling us they can make big power, and it turns out they mean for something like 1/100th of a second with only 1 channel running, they are just playing the phony specs game to impress those who don't know better.  As always, buyer beware!

These clowns at Expansion-Solutions aren't alone, either - a lot of sleazy characters are loose in this business, and a good clue to help identify them is throwing around a bunch of numbers that don't add up.

A slightly different twist is where some manufacturers throw around numbers that their equipment just won't make, but that's a little harder to tell on your own.  Just look at WAVAC or Krell for examples of that...

So who is impressed with phony specs?  Those who don't know what the numbers mean, that's who - and that's who the manufacturer wants to snare!

In the end, a good assessment of a product needs real, verifiable, no-kidding honest numbers, and a careful, critical listening test.  I also like to look at circuit topology & read the component-by-component circuit description.  And I never look twice at a product that won't give me schematics & circuit descriptions.

[speaker]

Frank VanA is right, of course - it is, most certainly, smoke and mirrors.  Power ratings are all about standards, measured under repeatable laboratory conditions, not (subjective & non-repeatable) listening conditions.

So, no, we don't listen to a 250W sine wave.  The point is, power ratings are measured with sine waves - and with both channels driven, and continuously.  Doesn't matter at all whether we listen like that: It's a STANDARD, get it?

So when a manufacturer like this  ...

FrankVanA made clear that this product could not work as stated on a standard 120VAC outlet. Would a 1500W hairdryer also not work when plugged into the same outlet as it presents a continuous draw, not peak?

There is no reason to disbelieve that a product rated @ 125W x 7 could not work as stated unless either of you have measured it and verified that it does not meet it's specification. If so, please post your findings.

speaker

[DVV]

It seems the spec game is running amok out there (again!).

Despite opinions to the contrary, it was not started by the Chinese, although they took it to its logical, albeit absurd pinnacle. So we can see small PC setups, fed from a dinky little transformers in a plastic boxes, deliver "3,700W P.M.P.O." (Peak Modulated Power Output, whatever that means in their interpretation, and Tesla must be turning in his grave).

High end, otherwise reputable manufacturers, are far from being immune. For example, Scandinavian manufacturers in general love to boast of their amps' high current delivery capability, so you see specs like 1,000W into 1 ohm; you have to read harder to see added "for 1 milisecond". I refer to Electrocompaniet's 250W amp, which is otherwise an excellent sounding amplifier.

This is very illustrative in many ways. For one, it shows how absurdly short and totally useless time intervals are given to make specs look great, even if they are in verifiable fact quite true. Nor are official specs helping much; for example, IEC recommendations call for measuring peak power outputs in 20 mS intervals, which is obviously much better than 1 mS, but is still far to short to have any real meaning. To the best of my knowledge, no specification calls for REPETATIVE impulse power measurements, and anyone who has ever designed an amp will know what this means in terms of specifications.

The only specs which did call for that were the now all but forgotten DIN 45500 standards. They defined "music power" as the maximum available power, at less  than 3% THD at 1 kHz, for peaks occurring once in every four cycles, for a period of time no shorter than 10 minutes. While this could be said to define pre-clipping power, nevetheless it was far more demanding than what we have today.

As things stand, and what seems to have been overlooked in this discussion, are two factors. The first is the transformation factor of the power transformer(s), which always exists and which significantly modifies the relationship between the power drawn from the wall outlet and delivered at the tranformer secondaries; not to get into a lengthy discussion, as a general rule of thumb you'll be safe in assuming it to be approximately 1.41 times, meaning that if an amp draws 1,000 VA from the wall outlet, it's very likely to be able to deliver some 1,400 VA to the power supplies.

The second is the non-repetative nature of such measurements. This is very important insofar that it allows the internal amp power supplies to be drained by a single burst with complete disregard to what happens next. In real life, what would happen next is that the now discharged capacitors would need to be recharged, which would tax the power transformer, and would in the meanwhile leave the amp breathless, with little power reserve, and God alopne know, if even He, with what kind of filtering from caps which are still recovering.

To give you an idea of the differences, if one of my own designs is made to peak out from a constant sine wave power output, it will peak out at 520W/2 ohms in a single burst, where it will run out of steam due to supply rails. But if the same amp is made to peak out from zero output, it will deliver 592W/2 ohms. Lastly, if it is made to peak out repetitatavely in 1-in-4 cycles, it will deliver approximately 480W/2 ohms. And it will do so only because I am a power supply freak, and use a 500 VA high efficiency toroid per channel, with a full wave bridge rectifier for each supply line (two per channel), followed by 50,000uF of capacitance, and with voltage gain stages and the predriver fed from separate, fully regulated power supply lines. The time interval used was 50 mS, still too short for me, even if two and a half times longer than IEC norms call for.

My old Harman/Kardon 680, integrated amp which was never sold in N. America for reasons which escape me, is said to deliver 85/130W into 8/4 ohms. It will deliver, in non-repetative impulses, 135/270/521/586 watts into 8/4/2/1 ohms. In repetative impulses, it will deliver 132/252/490/501 watts into 8/4/2/1 ohms. These are actually outstanding figures for a series manufactured model, the price of which was way below high end.

Cheers,
DVV

[BradJudy]

Since my guess that this product uses the d2audio module was backed up a bit, here are the specs direct from d2audio:

http://www.d2audio.com/files/productSheets/22-D2-PS-XR125-v1.6.0-web.pdf

As the photo implies, this module is used in the Harman/Kardon DPR-2005 as well as other products.

[Dan Banquer]

Given the spec's on the data sheet link provided by Bradjudy I think it could well be real. The typical Class AB power amp with it's linear unregulated power supply is typically about 30% efficent, and what I mean by that is if you drive the speaker with 30 watts of power it will take approximately 100 watts  of power from the AC line. The amps in question are switchers (often misnamed digital amps) and the 93% efficency quoted by the spec sheet is definetly possible. If the power supply of the unit in question, which is probably also a switching power supply is up to the task, then yes those kind of numbers are possible.
   These days the great bulk of sound reinforcement amps are switchers and this is due not only for the need for efficency, but lighter weight so the roadies don't file workman's comp claims due to the heavy weight demanded by high power linear designs.
   Please note that the above says nothing about the "quality" of power, just the ability to produce "raw" power.
                   d.b.

[avahifi]

Lets try again with a little basic electrical math  (no fun at all of course).

True RMS power equals [(peak voltage swing times .707) squared] divided by load resistance.  For example, a Fet Valve 350EXR swings about plus and minus 66 volts into 8 ohms (both channels driven).  The RMS power then is (65 x .707) squared, quantity divided by eight equals 272 watts per channel into 8 ohms, both channels driven.  Current equals RMS voltage divided by load resistance which equals about 5.8 amps of current thru the loudspeaker.  (whoops, fried speaker by the way).

If you only drive one channel, the peak voltage goes up to about 70V and the RMS power to about 306 watts.  Peak power (forget about multiplying by .707) then would be 612.5 watts into 8 ohms, or 1225 watts into 4 ohms per channel and adding the two is 2450 watts (pretty impressive) and this looks like the way that 7 channel amp is rated.

Now to go back to the 7 x 125 watt into 4 ohms amp.  If we translate the power rating back into true RMS power into 8 ohms terms, per channel, all channels driven at the same time, the numbers come out 22 volts peak and that yields all of an impressive 30 watts per channel RMS into 8 ohms.
And that is assuming 100 percent efficiency from the power supply, hardly likely.  If we assume a 90 percent efficiency of the power supply, and 100% for the audio channels, the peak voltage swing drops to about 19.8V and the true RMS power into 8 ohms drops to about 25 watts per channel

How many of you are going to get really excited about a 25 watt per channel rated 7 channel amplifier?  125 watts per channel is much more fun, even if it is done with smoke and mirrors.

All I am trying to tell you is that with multichannel amplifiers its very likely that you are not getting even close to what you think you are paying for in true power.  Go back and read my Audio Basics editorial from years ago, "Seven Shiny Pennies".  http://www.avahifi.com/root/audio_basics/1998-10_seven_shiny_pennys.htm  The scam is still working just great.

Frank Van Alstine

[jackman]

Lets try again with a little basic electrical math  (no fun at all of course).

True RMS power equals [(peak voltage swing times .707) squared] divided by load resistance.  For example, a Fet Valve 350EXR swings about plus and minus 66 volts into 8 ohms (both channels driven).  The RMS power then is (65 x .707) squared, quantity divided by eight equals 272 watts per channel into 8 ohms, both channels driven.  Current equals RMS voltage divided by load resistance which equals about 5.8 amps of current thru ...

Frank, I hate it when you get all logical and scientific!  It ruins all of the romance and trickery that I love about this hobby.  Can you please come up with a modification that will add to the "emotional" factor of your amp?  How about the "toe tapping" factor?  Is there a measurement for these things?  

Just kidding, I appreciate your non-nonscience (hehe) view on audio.  Hopefully, more manufacturers will follow your lead in this area, although I'm not holding my breath.  

[skrivis]

Lets see, 125 watts into 4 ohms pulls about 5 amps of continuous current from the amplifier.  Times seven channels requires 35 amps of current.

Just wondering where all the current is coming from?  Not very likely from a standard 15 amp rated residental AC wall outlet for sure.

Possibly from smoke and mirrors?  Or am I overlooking something?

Frank Van Alstine

You forgot the Magic Dust (TM).

You probably also forgot the expensive freako wires, magic capacitors, Peter Belt electret foil, and the magic AC cable that makes it all possible. Some nude attentuators to top it off? Maybe they wrote "OK" on the inside of the chassis and that made everything wonderful.