Class D Amp Specs

[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.

[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!

[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.

[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.

[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.

[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.

[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.

[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

[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.

[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.

[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

Actually I think you're off by a factor of ten. IIRC there was some research years ago that indicate 10% was the level of distortion that listeners considered the limit of usability and 1% was the threshold for fairly reliable identification (i.e. better than random guess).

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.

[dpasek]

Re: Class D Amp Specs

Big wattage numbers sell product.

So it seems.
I found a comment in an EE-Times article to that effect:
"Amplifier manufacturers will sometimes specify the output power at a higher level of THD in order to allow them to advertise a higher output power. A clipped sinusoidal output waveform with 10% THD has an average output power 28% higher than an undistorted sine wave output from the same amplifier."

[dpasek]

Re: Class D Amp Specs

No . . . there is no "transient response" past clipping.

I'm not talking about clipping in this part of my comment. It seems that I diverged without sufficient context change.

[Deward Hastings]

Re: Class D Amp Specs

Wouldn't it be a more meaningful indication of transient response to measure the response to some form of impulse stimulus

No . . . there is no "transient response" past clipping.