[Can Junkie]

I noticed that my udac-2 seems to run cooler on my laptop than my home tower. Settings are the same on both machines too. It never gets hot, just a little warm to the touch as has been reported up here many times by others. Any ideas as to why the temp difference between the two machines?

 

[HamilcarBarca]

[removed: I misread the question]

 

[HamilcarBarca]

Quote:

I noticed that my udac-2 seems to run cooler on my laptop than my home tower. Settings are the same on both machines too. It never gets hot, just a little warm to the touch as has been reported up here many times by others. Any ideas as to why the temp difference between the two machines?

 
If the volume produced by your headphones from the two systems isn't the same, the amplifier must be delivering different amounts of power. Increasing power delivery increases the heat produced. As an example, if one sounds sound twice as loud, the amplifier delivers ten times as much power. This is an exaggerated example because you'd notice the very obvious difference.
 
The volume and other settings may be the same on two systems but that's not the whole story. If you like, set the controls on your two computers so your headphones' loudness, measured by an SPL (Sound Pressure Level) meter, is the same from both. The amp's temperatures should then be the same.  
 
You might like Wikipedia's articles on Sound Pressure and  Decibel or you might not.

 

[Can Junkie]

If the volume produced by your headphones from the two systems isn't the same, the amplifier must be delivering different amounts of power. Increasing power delivery increases the heat produced. As an example, if one sounds sound twice as loud, the amplifier delivers ten times as much power. This is an exaggerated example because you'd notice the very obvious difference.
 
The volume and other settings may be the same on two systems but that's not the whole story. If you like, set the controls on your two computers so your headphones' loudness, measured by an SPL (Sound Pressure Level) meter, is the same from both. The amp's temperatures should then be the same.  

You might like Wikipedia's articles on Sound Pressure and  Decibel or you might not.

Well you did make me think about something. I read up here that it is best to run the comp sys sound all the way up to get the highest bit transfer rate when using a DAC. (wonder if that is true). Anyway, just started doing that on laptop so that would mean I was using the DAC amp section more on the home tower as I did not have tower vol all the way up. Could be the reason in different DAC operating temps between the two machines.

 

[HamilcarBarca]

Quote:

Well you did make me think about something. I read up here that it is best to run the comp sys sound all the way up to get the highest bit transfer rate when using a DAC. (wonder if that is true). Anyway, just started doing that on laptop so that would mean I was using the DAC amp section more on the home tower as I did not have tower vol all the way up. Could be the reason in different DAC operating temps between the two machines.

 
I read recently that to maximize the effective (not actual) bit-rate transfer to the DAC, it's better to avoid digital volume controls.
 
Here's my non-expert interpretation. I think the problem is digital volume controls may cause audio samples to be bit-shifted to the right if the volume isn't maximized. If this is what's happening, the advice is correct. I may have misunderstood the details, but not the consequences: A loss of audio resolution when the samples are presented to the DAC.
 
As an non-technical analogy, we want to send 16 gallons of water (as the effective transfer rate) in each 16-gallon bucket (our actual transfer rate.) We don't want to send 12 gallons at a time (a reduced effective transfer rate) in the 16-gallon bucket. We'll let the analog control decide if it wants all that water.
 
Whether this is actually audible is left as an exercise for the listener. Wednesday, I followed the advice you mentioned. I set all the computer's volume controls to 11 and use only the analog controls on my new E5.