I wrote to Atoll and conveyed the skepticism posted here about the Class A operation of the Atoll. They replied:
From Atoll engineers:
"Hello, Thank for for this information.
This is one of the most current mistakes people make about our amplifiers; they compare the size of our heat-sink to a single one; this is nonsense regarding to thermal dissipation because when you use a single, big heat-sink you have to put in isolation components that increase (a lot) the thermal resistor. For that reason, and on that point they are correct -- in order to have the same dissipation you would require an almost 10 times bigger heat sink for each channel; but with our trick, the transistors are transferring about 100% of their heat to the heat-sink with no waste of energy. You'll find attached a measurement that shows the distortion when power is rising; as you can see (in the picture), the distortion is under 0,002% up to 50W on both channel. Best regards. ATOLL Team"
I don't think I can post pictures here, but anyone who'd like to see it can P.M. me.
From Atoll engineers:
"Hello, Thank for for this information.
This is one of the most current mistakes people make about our amplifiers; they compare the size of our heat-sink to a single one; this is nonsense regarding to thermal dissipation because when you use a single, big heat-sink you have to put in isolation components that increase (a lot) the thermal resistor. For that reason, and on that point they are correct -- in order to have the same dissipation you would require an almost 10 times bigger heat sink for each channel; but with our trick, the transistors are transferring about 100% of their heat to the heat-sink with no waste of energy. You'll find attached a measurement that shows the distortion when power is rising; as you can see (in the picture), the distortion is under 0,002% up to 50W on both channel. Best regards. ATOLL Team"
I don't think I can post pictures here, but anyone who'd like to see it can P.M. me.