Power amps-> power consumed vs output power.

[Myron Samila]

Hi all,

I service professional audio power amps. And I am always asked the question, how can this
amplifier which states a power output of 1200 watts/channel at 4 ohms (both channels
driven 20hz-20khz) can actually put out 2400 watts total when the power consumption is
only 1800 watts.

?!?!?

thanks.

--
Myron Samila
Toronto, ON Canada
Samila Racing
http://204.101.251.229/myronx19

 

[Jim Thompson]

On Mon, 8 Dec 2003 14:02:22 -0500, "Myron Samila"
<myronx19@removenospamhotmail.com> wrote:

Hi all,

I service professional audio power amps. And I am always asked the question, how can this
amplifier which states a power output of 1200 watts/channel at 4 ohms (both channels
driven 20hz-20khz) can actually put out 2400 watts total when the power consumption is
only 1800 watts.

?!?!?

thanks.

It's called IHFM rating ;-) The trick wording is "instantaneous
bursts"... in other words it's a lie.

'IHFM Music Power Output Rating

"The IHFM Music Power Rating uses a technique that makes power
measurements at a frequency of 1,000 cycles per second to indicate the
capability of an amplifier to handle instantaneous bursts of music
power peaks. Since no distortion levels are defined in this method,
the Heath Company has performed its IHFM music power ratings at the
same level of distortion as is maintained in its own system of
standards for the Hi-Fi use category. That level is 0.7% total
harmonic distortion at 1 KC. We believe that this figure is the
maximum total harmonic distortion tolerable for high fidelity
applications.

"In determining the advertised power ratings of Heathkit amplifiers
using Heath and IHFM standards, we measure a group of amplifiers
selected by statistical techniques to represent normal variations that
can be expected in production. These measurements are averaged and the
advertised power rating is the nearest whole number of watts.

"You will also note that the Heath power Output Rating figure is
always lower than that obtained for the IHFM Music Power Rating. This
indicates Heath's policy of conservatism in advertised power ratings
for its power amplifiers. It is also another assurance to you, our
customer, that Heathkit products have quality that you can depend on
and trust--with guaranteed performance specifications."


Excerpted from 1962 Heathkit catalog '

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Myron Samila]

Thanks for the explanation.

I've run a large power amp with a 1khz input signal, measured the voltage at the output
and yes, the output power was less than its rated output. When I drove it harder, it
tripped the main circuit breaker (at the panel).


I have a Bryston 3B power amp for my home system, it is rated at about 150watts/channel.
It has a massive dual power supply, it is an older model (not torrodial transformer type),
has quite the DC filtering as well.

This amp is under-rated, for the 150 watts it produces, it will blow away any integrated
amp in "fidelity". The low frequencies are well defined, and sounds "thick". It is a
Bi-Polar design. Bryston is a Canadian made amplifier, 20 year warranty, just a power
switch and gain control via screwdriver (on the late 80's 4B).

--
Myron Samila
Toronto, ON Canada
Samila Racing
http://204.101.251.229/myronx19
"Jim Thompson" <invalid@invalid.invalid> wrote in message
news:doj9tvkiba815rh1kj143t4t16ep02tr2e@4ax.com...

On Mon, 8 Dec 2003 14:02:22 -0500, "Myron Samila"
myronx19@removenospamhotmail.com> wrote:

Hi all,

I service professional audio power amps. And I am always asked the question, how can
this
amplifier which states a power output of 1200 watts/channel at 4 ohms (both channels
driven 20hz-20khz) can actually put out 2400 watts total when the power consumption is
only 1800 watts.

?!?!?

thanks.

It's called IHFM rating ;-) The trick wording is "instantaneous
bursts"... in other words it's a lie.

'IHFM Music Power Output Rating

"The IHFM Music Power Rating uses a technique that makes power
measurements at a frequency of 1,000 cycles per second to indicate the
capability of an amplifier to handle instantaneous bursts of music
power peaks. Since no distortion levels are defined in this method,
the Heath Company has performed its IHFM music power ratings at the
same level of distortion as is maintained in its own system of
standards for the Hi-Fi use category. That level is 0.7% total
harmonic distortion at 1 KC. We believe that this figure is the
maximum total harmonic distortion tolerable for high fidelity
applications.

"In determining the advertised power ratings of Heathkit amplifiers
using Heath and IHFM standards, we measure a group of amplifiers
selected by statistical techniques to represent normal variations that
can be expected in production. These measurements are averaged and the
advertised power rating is the nearest whole number of watts.

"You will also note that the Heath power Output Rating figure is
always lower than that obtained for the IHFM Music Power Rating. This
indicates Heath's policy of conservatism in advertised power ratings
for its power amplifiers. It is also another assurance to you, our
customer, that Heathkit products have quality that you can depend on
and trust--with guaranteed performance specifications."


Excerpted from 1962 Heathkit catalog '

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Steve Dunbar]

Myron Samila wrote:

Hi all,

I service professional audio power amps. And I am always asked the
question, how can this amplifier which states a power output of 1200
watts/channel at 4 ohms (both channels driven 20hz-20khz) can actually put
out 2400 watts total when the power consumption is only 1800 watts.

The same way that a 120V 15A outlet can power a "5 horsepower" air
compressor.


--
Steve

 

[Myron Samila]

well, really, in Canada, an electrical item must be de-rated for use (unless it is hard
wired). Meaning, an 1800 Watt wall outlet (15A/120V) can only supply a 1500 W device.

So, 1500 W only gives you 2 hp at 120V.

They write 5HP peak. ?!?! hehehe, yeah, what ev.....

I had a professional table saw that had a GE 1HP induction motor, when that thing powered
up, it would draw much more than 12 A, for one HP!! Cuz its a real motor.

I have a Devilbiss air compressor, it is a 5hp 120V model, ?!?! oh well, its really only 2
hp I guess (1hp=746W)

--
Myron Samila
Toronto, ON Canada
Samila Racing
http://204.101.251.229/myronx19


"Steve Dunbar" <stvdnb@NOSPAM.yahoo.com> wrote in message
news:vtd49fa5v7m55@corp.supernews.com...

Myron Samila wrote:

Hi all,

I service professional audio power amps. And I am always asked the
question, how can this amplifier which states a power output of 1200
watts/channel at 4 ohms (both channels driven 20hz-20khz) can actually put
out 2400 watts total when the power consumption is only 1800 watts.

The same way that a 120V 15A outlet can power a "5 horsepower" air
compressor.


--
Steve