Explanation for Class G amplifier heat differences between phono source & others?

Would my class G Creek 100A integrated be giving off more heat when the phono source is used (as compared to other sources--e.g. tuner, cd, digital) because the amp and pre sections have to amplify a smaller input source with phono?  

I am just curious.  I have no issues.  The amp runs so cool with non-phono sources that you have to work to make it break a sweat.  This is not the case with phono sources. 

Thanks much!!