Chip amp voltage vs amperage

I have a very limited understanding with electronics and am eager to learn more. I would like to know more about voltage x amperage. I know that voltage x amperage = watts. Supposing a chip will give 100 watts and the recommended rail voltage is 50 volts. Assuming this to be true, 2 amperes will provide approximately 100 watts. Supposing this same chip is only supplied with 20 volts or is supplied with 70 volts. Can the same wattage be aquired with less or more current respectively? If an amp is supplied less voltage than recommended as in my present situation, does the chip draw an increased amount of current similar to an automobile in low gear using extra engine RPM to compensate for less wheel rotation?
If I am using 22-0-22 transformers per speaker, should I be using a 50 watt chip being pushed harder instead of a 100 watt chip being worked lightly?
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You're leaving out some important variables. I suggest having a look at the May 2004 revision of the LM3886 datasheet. In it you'll find graphs of things such as output power vs. supply voltage, supply current vs. supply voltage, clipping voltage vs. supply voltage, etc.
And remember Ohm's law V=I/R. If the impedance of the circuit and load remains the same, a lower voltage will result in a lower current.
My answer to the last question... I would guess it mostly depends on the particular chip amp, or chip amp and speaker combo. Just like some horses are bred to trot, and some to gallop.
Oh yes. I forgot that Votge is required to cause current! I had tunnel vision from measuring my rail voltages. I watching for voltage drop while a increased the gain on my amp. I was thinking that if I run out of current from my transformer, my voltage would drop. From there, I thought that if I had twice the voltage, I wouldn't get the same drop. Now that you woke up my brain, I realise that the current would also be increased with the voltage. I will have to spend more time reading datasheets, I have found them to answer quite a few questions.