Class D Amp Specs

[Sydney]

Re: Class D Amp Specs

It's been that way for a long time; there have been numerous industry attempts to standardize the wattage rating system of audio amplifiers.
Manufacturers have found ways to produce high wattage numbers which are far more impressive for sales purposes than listing db gain.

[dpasek]

Re: Class D Amp Specs

This may be the real answer (also from EE-Times):

"FTC and EIA specifications only require amplifiers to operate continuously at 1/8 of their rated output power. This allows designers to save money in the design of both the amplifier and the power supply. Most consumer amplifiers use this approach."

This would explain the common use of the absurd looking 'peak power' ratings.

[dpasek]

Re: Class D Amp Specs

It's been that way for a long time; there have been numerous industry attempts to standardize the wattage rating system of audio amplifiers.
Manufacturers have found ways to produce high wattage numbers which are far more impressive for sales purposes than listing db gain.

I remember when amplifiers that were intended for consumer home use were specified as "watts RMS at .05% THD or less" (which doesn't say anything about transient response.) Maybe those days are long gone. Oh, and then wasn't there an 'IHS' power? Amps for automotive use seem to have always been rated for peak power and maximum hype.

Most consumers don't know a dB from a 'Blah-blah' and couldn't tell a logarithm from a 'log-a-what' so we all get reduced to the least common denominator.

[Brian Steele]

Re: Class D Amp Specs

Amps for automotive use seem to have always been rated for peak power and maximum hype.

Not really. The good ones now are rated according to CEA2006 - see http://www.cea2006.com/cea2006.htm

[Whitneyville1]

Re: Class D Amp Specs

How about the Mackie power amps we have in our church? 1000 watts per channel continuously 100% power factor sinewave from 5Hz to 35,000 Hz @ .003% THD with 350% peak overload for 33% operation @ .005% THD, Class AB2 Operation. Of course you can cook bacon over the cooling fans....
What I really love are the new DTV final amps. Channel 9's "blockhouse" I've been in. 7.8 megawatts effective output at 0% distortion. The tube operates with 470,000 volts on the plate and 500 gallons per minute of water thru the cooling jacket. It's 18' tall and 8' in diameter, and the corona makes the air the prettiest violet at night you've ever seen, feeding the second tallest tower in the US.

[ROTECH]

Re: Class D Amp Specs

Not really. The good ones now are rated according to CEA2006 - see http://www.cea2006.com/cea2006.htm

Thank you Brian. Glad somebody else recognized this.

This CEA2006 rating was well needed because audio competition watt rating classes were a crapshoot at best, however it was not able to sway the general automotive audio consumer away from flea market brand amplifiers rating their 10A draw amplifiers at about 40000watts.

[fastbike1]

Re: Class D Amp Specs

I'm talking about home audio use.

That's possible. It depends on application, program source, and the tolerance of the individual listener. A boom box user listening to rap probably won't care. It also seems that you can get away with using a class C amp in a bullhorn and the voice will still be understandable for communications purposes. But these are both well outside of 'audiophile' territory.

[Sydney]

Re: Class D Amp Specs

Most consumers don't know a dB from a 'Blah-blah' and couldn't tell a logarithm from a 'log-a-what' so we all get reduced to the least common denominator.

Perhaps it is an inevitable consequence of business.
Automobiles are sold based upon engine horsepower NOT the power at the wheels.
Since there really isn't a standard speaker load - Electronic manufacturers have often used that reality to petition for alternative testing procedures that usually produce larger numbers. And argued that requirements like preconditioning are not relevant.
Often manufacturers find ways to modify the test conditions to produce better performance figures.

[Face]

Re: Class D Amp Specs

Perhaps it is an inevitable consequence of business.
Automobiles are sold based upon engine horsepower NOT the power at the wheels.

Power at the wheels doesn't win races either as things like a high stall torque converter and large rear will skew that too.

[Pallas]

Re: Class D Amp Specs

Power at the wheels doesn't win races either as things like a high stall torque converter and large rear will skew that too.

What is this "torque converter" thing?

Certainly nothing that exists on any automobile worth anything!

[Sydney]

Re: Class D Amp Specs

...will skew that too.

Yes, and that's the point - using a number that is unqualified or creating a testing methodology that is not representative of typical operating conditions to obtain desired results.

[PWR RYD]

Re: Class D Amp Specs

Power at the wheels doesn't win races either as things like a high stall torque converter and large rear will skew that too.

Than what does win races

[Sydney]

Re: Class D Amp Specs

Than what does win races

Well I think it can be agreed that the focus is different if the race is a 1/4 mile vs 24 hours on a closed course vs off-road.
One favors short term power over parts durability and endurance.

[PWR RYD]

Re: Class D Amp Specs

Length of the race (time or distance) has nothing to do with it. In every form of racing the goal is to have both superior power and adequate endurance. A part's failure at 3 seconds into a 1/4 mile race can be just as bad as a part's failure 23 hours into a 24 hour race. Having 20% less power than your competitors is just as much of a disadvantage regardless of the type (length) of racing. FIA, or F1, or NASCAR, or NHRA... they are all trying to win the power vs. parts life game.

[Sydney]

Re: Class D Amp Specs

This is an obvious divergence:
Does anyone think an engine producing 8000 hp short term can do so for 24 hours ( the engines are torn down and rebuilt in 75minutes after every run )...
http://www.hotrod.com/techarticles/e...d/viewall.html

By the same token an amplifier test can produce a high short term number for domestic persuation but that operating condition is not long term. Amplifiers have protection ( or should ) for being driven beyond a "performance envelope" .
The better amplifier manufacturers publish a variety of test conditions including extreme ( short term ), or continuous duty or fault tolerance.
Any semiconductor manufacturer knows the relationship between operating temp and device life.
OEM Class D amp manufacturer's are often of the opinion that there is too much emphasis on amplifier distortion figures, considering the level of distortion in loudspeakers is much higher.
They also advocate that the testing methodology for Class D is not the same as Class A & AB.