Reality check!!

[crashguy]

Is it just me, or are there some companies out there in audioland that rate their products such that they break every law of physics there is to be broken.

Seriously though. A powered sub rated at 2600w peak?? Gimmie a break!! Not unless you have it plugged in to a 20A circuit breaker in your home. The most power available out of a 15A breaker is 15A X 120V = about 1800w. This assumes you actually HAVE 120V, not 108V or 111V, coming out of the wall; and it also assumes that there is no other plugs wired into that circuit drawing power. 15A is 15A is 15A. No way around that. Now, I'm no electrician, but if the breaker trips if more than 15A is drawn through it, that's all you're going to get folks!

Now I would like to start this paragraph off with a qualifier. I like Harmon/Kardon products. I think they are quality pieces as I have stated on this forum in the past. But can someone tell me where they come up with suggesting that their recievers can deliver 55 amps of "peak current." I'm sure they don't mean to suggest that their receivers can manufacter power in excess of 40A.

I don't get it. There must be some technical electrical engineering way to make these claims make sense. HOWEVER, the impression it leaves with the consumer is that the amp can put out 55A of current. Correct me if I'm wrong here, but this sounds to me to be impossible.

Why post this thread? Because I think these forums are for educating each other about our hobby. Lets face it, most of us here are the people our friends come to when they have money burning a hole in their pocket for audio or home theater gear. We should know what we are tallking about.

By the way, if I don't know what I'm talking about, feel free to educate me.

I feel better.....

 

[crashguy]

I guess I should have posted this in "The Steam Vent."

See, I'm continuing my education.....

 

[BMXTRIX]

I don't get electronics fully, but typically, don't good amplifiers have onboard capacitors or something that store extra current inside of them for times when extra power is needed? 'Peak' current is not the same as continuous, and relates to something like a canon shot that may draw heavily for a moment and drain the capicitor within the sub / sub amplification section of the product.

Now, that may just be completely wrong, but if I were designing a high end sub and wanted to provide smooth continous power with the ability for high power occassional draws of electricity, I would add the ability to store the extra power that would be necessary within the electronics of the sub.

 

[WmAx]

But can someone tell me where they come up with suggesting that their recievers can deliver 55 amps of "peak current." I'm sure they don't mean to suggest that their receivers can manufacter power in excess of 40A.

All that matters is the sum power available from the wall outlet. You can lower voltage and raise current or vice versa, by way of a simple transformer. For example, you reduce 120V to 30V, and with this 4:1 ratio of voltage reduction, you would gain a 1:4 current ratio. Now, 120V 15A input = 30V 60A output(minus small losses of the transformer).

Assume a 50% efficiency of actual power available by a standard CLASS A/B amplifier topology(most common), and about 30A would be potentially avaiable in a continous total current, or higher for a PWM switching amplifier(class D), which is about 80-90 percent efficiency. Of course, it's unlikely most consumer products will have a transfomer large enough to supply this type of power contiously, so the high current ratings are probably instaneous, based on the short reserve supply provided by the power supply capacitor bank.

-Chris

 

[crashguy]

See, now I learned 2 things. 1) Chris knows a lot more about electricity than me, and 2) I spelled RECEIVER wrong in my original post.

How does that go, I before E, except when... in the word RECEIVER???

 

[PENG]

If I remember correctly, those HK high currents are indeed instantaneous values. Chris already explained the power, voltage & current relationship as well as the effects of the capacitors.

Others, such as Denon, Onkyo & Yamaha, also claim high current capable, they just don't emphasize it as HK does. Even Sony, the TA-9000ES (U.K. version of the STR-DA9000ES) claimed their "extremely massive toroidal-core power transformer" can deliver 12 amps (obviously instantaneous only) per channel, or 84 amps total.

 

[mtrycrafts]

Is it just me, or are there some companies out there in audioland that rate their products such that they break every law of physics there is to be broken.

Seriously though. A powered sub rated at 2600w peak?? Gimmie a break!! Not unless you have it plugged in to a 20A circuit breaker in your home. The most power available out of a 15A breaker is 15A X 120V = about 1800w. This assumes you actually HAVE 120V, not 108V or 111V, coming out of the wall; and it also assumes that there is no other plugs wired into that circuit drawing power. 15A is 15A is 15A. No way around that. Now, I'm no electrician, but if the breaker trips if more than 15A is drawn through it, that's all you're going to get folks!

Now I would like to start this paragraph off with a qualifier. I like Harmon/Kardon products. I think they are quality pieces as I have stated on this forum in the past. But can someone tell me where they come up with suggesting that their recievers can deliver 55 amps of "peak current." I'm sure they don't mean to suggest that their receivers can manufacter power in excess of 40A.

I don't get it. There must be some technical electrical engineering way to make these claims make sense. HOWEVER, the impression it leaves with the consumer is that the amp can put out 55A of current. Correct me if I'm wrong here, but this sounds to me to be impossible.

Why post this thread? Because I think these forums are for educating each other about our hobby. Lets face it, most of us here are the people our friends come to when they have money burning a hole in their pocket for audio or home theater gear. We should know what we are tallking about.

By the way, if I don't know what I'm talking about, feel free to educate me.

I feel better.....

Yep, there is/was a sub rated to that power capability. There were several explanations of its meaning. It had to be at some special impedance condition that was never able to have, etc. Bogus claims in another word.

Receiver current ratings of such magnitude is also bogus. Just think of the power it would deliver. Power = current squared x resistance of speaker load in this case.
55A = 3025watts into a 1 ohm speaker and 24200 watts into an 8 ohm speaker. You buy that claims?

What are 'laws of physics' to a marketeer? Absolutely nothing

 

[WmAx]

While you are correct, there are theoretical conditions under which it's not quite so 'fictatious' situation as you make it out to be.

Let's assume a massive transformer/powersupply(not something you would find on any sanely priced equipment) and assume a theoretical 30V stepdown from:

120V INPUT @ 15A

5 channels @ 4 ohms, at 28volts

Sqr(Amperes)*Ohms = Sqr(7)*4=196 watts

5 channels equals a current production total of 35amperes potential continous output. That's not an unrealisitic estimate, assuming an A/B class amplifier, dedicated AC line with 120V on demand and an optimal amplifier power supply(this part is unlikely, however).

In, all that 35A output would result in 980 watts output under these specific conditions.

My math could of course be in error. Also, I have no idea what percentage of transformer output voltage is availalbe upon output stage(s). Hopefully someone knowledgable of amplifier design can fill in here....



-Chris

Yep, there is/was a sub rated to that power capability. There were several explanations of its meaning. It had to be at some special impedance condition that was never able to have, etc. Bogus claims in another word.

Receiver current ratings of such magnitude is also bogus. Just think of the power it would deliver. Power = current squared x resistance of speaker load in this case.
55A = 3025watts into a 1 ohm speaker and 24200 watts into an 8 ohm speaker. You buy that claims?

What are 'laws of physics' to a marketeer? Absolutely nothing

 

[plhart]

Peak power or peak current are yet more bogus terms that have been around sense the dawn of audiophilia. Peak power ratings reached their zenith in the late seventies, after the demise of the IHF (Institute of High Fidelity). Earlier on, If marketing guys really wanted an amplifier to have credibility they'd say IHF peak power. You betcha, J.C. Whitney; a 100 watt car amp for $19.95!

In the eighties the new governing body who tried to put some form of substance back into measurements was the EIA (Electronic Industries Association. (Today they are known as the CEA, Consumer Electronics Association, the guys who still put on the CES.) The EIA came out with a new measurement for power called Dynamic Power and "strongly suggested" to it's members that they begin using this new term with it's established measurement criteria. So during the eighties you'd often see two power measurements from the mainline companies, one for RMS and one for Dynamic. As I recall Dynamic Power is defined by a 10millisecond "on" duty cycle (the short surge time which yielded the highest number) followed by a 500 millisecond return to RMS value or just below.

Dynamic power was pretty good for a while, that is until a receiver or power amp company's sales and marketing guys kept asking for "more power, more amperage!" from designs which usually had the same power supply as before. (See my article on Product Managing Receiver Power Ratings .)

So now we see the re-emergence of peak power once again. A lot of this nonsense is just the internal result within companies of engineers and product mangers tiring of hearing the sales guys keep begging for MORE. They just cave and say (internally) "Yes, Mr Sales/Marketing, this receiver will put out XXXX amps when struck by lightning (the WSL rating). The Sales/Marketing guy says "Is that the same as peak power?" We say "It's anything you want it to be." And so it goes to print.

Understand that the EIA, now the CEA can only recommend methods of measurement. And if nobody has screamed (on behalf of the public) for several years the power rating/amperage situation can pretty much turn into the free-for-all it has once again become. Sigh........

 

[mtrycrafts]

While you are correct, there are theoretical conditions under which it's not quite so 'fictatious' situation as you make it out to be.

Let's assume a massive transformer/powersupply(not something you would find on any sanely priced equipment) and assume a theoretical 30V stepdown from:

120V INPUT @ 15A

5 channels @ 4 ohms, at 28volts

Sqr(Amperes)*Ohms = Sqr(7)*4=196 watts

5 channels equals a current production total of 35amperes potential continous output. That's not an unrealisitic estimate, assuming an A/B class amplifier, dedicated AC line with 120V on demand and an optimal amplifier power supply(this part is unlikely, however).

In, all that 35A output would result in 980 watts output under these specific conditions.

My math could of course be in error. Also, I have no idea what percentage of transformer output voltage is availalbe upon output stage(s). Hopefully someone knowledgable of amplifier design can fill in here....



-Chris

No, in this case it is possible when all channels are combined to get the 35A, not one channel.
I am very doubtfull that the amp will do 200watts simultaneously into all the channels.

 

[PENG]

Sqr(Amperes)*Ohms = Sqr(7)*4=196 watts

5 channels equals a current production total of 35amperes potential continous output.

-Chris

I thought Crashguy was talking about HK receivers. If you visit the HK site and read up on the product description of one of their receiver, e.g. AVR7300, you will see that they specify the +-75 amps as "instantaneous" current. Definitely not "continuous". Whether instantaneous means milli seconds, micro seconds, pico seconds or shorter, we don't know. Other than that, your math is correct.

 

[mtrycrafts]

I thought Crashguy was talking about HK receivers. If you visit the HK site and read up on the product description of one of their receiver, e.g. AVR7300, you will see that they specify the +-75 amps as "instantaneous" current. Definitely not "continuous". Whether instantaneous means milli seconds, micro seconds, pico seconds or shorter, we don't know. Other than that, you math is correct.

Well, even that, 5625watts is in dreamland no matter how you slice it.

 

[xyntax]

let me remind everybody that OHMS ratings of speaker is not RESISTANCE but IMPEDANCE. its Z not R.