question about amp efficiency

[deathcards]

Why do manufacturers only rate it at 4 ohms why not at 1 and 2 ohms also this has kinda got me wondering seeing as not every1 runs their amps at 4 ohms i think it would give us a good idea on how much electrical we would need to get full/rated output at that ohm load

[Noobtastic14]

The amp is more efficient at 4ohms so they post that number as a baseline for sales. Some amps would never get bought if the 1ohm 12.8v efficiency was posted.

-Drew

[MrSkippyJ]

Same reason any company only posts the best stats. Car companies do it with gas mileage too. They should have a fuse requirement, that will let you know how much power you need.

[Miguels]

i was reading on a website that A class amps are less efficient at 30 to 35% B class was better at 60% and class D amps was 90%

[STEvil]

Those numbers are all wrong, but in general Class A are horrible inefficient, B are a bit better, and D are much better.

A's also sound the best, B's decent, and D's like crap... if you're doing SQ

[deathcards]

if you contacted the company do you think they would give you those numbers?

[Miguels]

i got this from online

Efficiency

Efficiency is a measure of how much of the power source is usefully applied to the amplifier's output. Class A amplifiers are very inefficient, in the range of 10–20% with a max efficiency of 25% for direct coupling of the output. Inductive coupling of the output can raise their efficiency to a maximum of 50%.

Drain efficiency is the ratio of output RF power to input DC power when primary input DC power has been fed to the drain of an FET. Based on this definition, the drain efficiency cannot exceed 25% for a class A amplifier that is supplied drain bias current through resistors (because RF signal has its zero level at about 50% of the input DC). Manufacturers specify much higher drain efficiencies, and designers are able to obtain higher efficiencies by providing current to the drain of the transistor through an inductor or a transformer winding. In this case the RF zero level is near the DC rail and will swing both above and below the rail during operation. While the voltage level is above the DC rail current is supplied by the inductor.

Class B amplifiers have a very high efficiency but are impractical for audio work because of high levels of distortion (See: Crossover distortion). In practical design, the result of a tradeoff is the class AB design. Modern Class AB amplifiers commonly have peak efficiencies between 30–55% in audio systems and 50-70% in radio frequency systems with a theoretical maximum of 78.5%.

Commercially available Class D switching amplifiers have reported efficiencies as high as 90%. Amplifiers of Class C-F are usually known to be very high efficiency amplifiers. RCA manufactured an AM broadcast transmitter employing a single class-C low mu triode with an RF efficiency in the 90% range.

More efficient amplifiers run cooler, and often do not need any cooling fans even in multi-kilowatt designs. The reason for this is that the loss of efficiency produces heat as a by-product of the energy lost during the conversion of power. In more efficient amplifiers there is less loss of energy so in turn less heat.

In RF linear Power Amplifiers, such as cellular base stations and broadcast transmitters, special design techniques can be used to improve efficiency. Doherty designs, which use a second output stage as a "peak" amplifier, can lift efficiency from the typical 15% up to 30-35% in a narrow bandwidth. Envelope Tracking designs are able to achieve efficiencies of up to 60%, by modulating the supply voltage to the amplifier in line with the envelope of the signal.

[deathcards]

i think we got off topic from the ?s i am asking

[STEvil]

No, they were answered on post number 2.

[deathcards]

No, they were answered on post number 2.

check post 6