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In Reply to: Power Consumption in Class A Solid State Amps.....Help needed. posted by rmzidann on April 21, 2007 at 11:59:14:
Depends, but you could probably figure around 400 watts power consumption at full power output if really running in pure class-A (not many do).
Follow Ups:
Yes, it's full class A. However, I probably would use it with an 88 db, 6 ohm speaker and I do not listen to loud levels. It's an integrated amp.
I believe I am right on this, when ON it will draw 80 watts, 1.5 amps, all the times it is on. That is the draw from your meter, so if it is on 24/7 it will draw 1920 watts a day. Any peak watt draws come from the caps and won't be reflected by the meter. An A/B amp has a low draw until power is needed, then demand goes up. The class A amp will all so produce more heat into the room. I use a class A Threshold 100 watt amp that runs the front speakers in my HT I like the fast responce that a class A amp delivers.
"The power consumption is unrelated to the output power: at idle (no input), the power consumption is essentially the same as at high output volume. The result: a considerable amount of power is radiated by the heat sinks." (Wikipedia)http://en.wikipedia.org/wiki/Electronic_amplifier
In real life, here are the specs for a pure class-A 150W/channel amp ...Technical Specification
Input Sensitivity 1.6v for full rated output
input Impedance 67 kohms
Slew rate up to 40v/us
Power supply at 4 ohms up to 16 amps
Instantaneous current supply up to 75 amps
Signal to noise ratio < 100dB
Power Consumption (idle) 175watts
Power Consumption (full rated power @ 8ohms) 720 watts
Power Output 20hz - 20Khz @8ohms 150 watts RMS per channel (both channels driven)
Weight 40Kgs
Dimensions 480 x 480 x 225mm
Does that amp run in pure class A?
That's kind of the point, there isn't a real definition. But yes, it is advertised as a pure class A amp, and doesn't differ in that regard from many other similarly advertised designs from big and small companies ...
So you won't be submitting a correction to Wikipedia?
just not necessarily right either :-)"Pure" is really a modifier that hasn't much meaning in this context. It might have been used at one time in an attempt to separate the shadier advertisers from the more consumer friendly advertisers, but nowadays it is just an advertising term. In the end, not many amplifiers, regardless of class-A "purity", consume the same power at idle as they do at full power, and at all loads. Bias levels change and adjust, and banks of transistors still change bias in most push-pull designs at high power levels when they aren't needed, unless it's just a resistor biased single-ended design like some of the very low power class-A amps.
The definition of Class-A is that the devices conduct current during 360 degrees of a sine wave cycle. This does not necessarily mean that the input power requirements are steady during variations in the output power. The belief in this relationship is due to circuit designs that are very old. These older designs generally have a bias point that does not intentionally change as the power level changes. Unfortunately this is not a very efficient design from a power consumption perspective or from a power vs. device cost perspective.As designs have developed over time techniques have been developed and utilized that allow compliance with the definition of Class-A that improve power efficiency and allow greater power output from a fixed number of devices.
"Power Consumption (idle) 175watts
Power Consumption (full rated power @ 8ohms) 720 watts
Power Output 20hz - 20Khz @8ohms 150 watts RMS per channel (both channels driven)"
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