[discoprince]

In my quest for a new portable DAC/AMP, I am looking at spec sheets and growing confused. I currently have a fiio e12 with a power output of 880mW/32 Ohms. I am interested in the Centrance HiFiM8 or the Theorem 720. The Theorem has a power output of 205mW @ 32 Ohms. My audioquest dragonfly has an output of 125mW @ 32 ohms. I've listened to each of these fairly extensively and each offer different sound and capabilities, with the theorem leaving me feeling like it blows the other two out of the water with its sound quality and power. On paper though, It doesn't quite compute. I also was interested in the RAL DAC/AMP that reports 38mW @ 68 Ohms, but this amp has had great reviews from people using it to drive reasonably difficult cans.
 
Can someone clear this up concisely? 

 

[PleasantSounds]

In simple terms, the power figure alone is pretty much useless - as you already experienced it.
 
The reason is that as the output power increases, so do distortions (and that relationship is non linear). Manufacturers state the output power at arbitrarily selected distortion level and not always publish it. So an amp with 250mW @ 0.001% THD may actually be more powerful than one with 800mw @ 0.1% THD.

 

[mikeaj]

Listed specs may not be completely honest or really listed in ways that are completely comparable, but that's likely not the most relevant issue here.
 
The thing to realize is that these are maximum levels possible by the electronics. The vast majority of people on most of these devices on most headphones aren't using anywhere close to the maximum levels. The amount of power supplied by the amplifier and the headphones determine the volume you get out. 10 mW from one source sounds as loud as 10 mW from another source. If you're only using 0.3 mW, it doesn't matter if a device is capable of 20 mW or 20 W into 32 ohms or whatever else. Hundreds of milliwatts into most headphones is unbearably loud and would require you to quickly take the headphones off your head. The louder you want to listen and the less sensitive the headphones (which headphones, actually?), the more power you need. You should try to look at what produces a decent signal at the levels you'll be using. Note that actual, audible sound quality differences between different electronics can happen but are frequently overstated.
 
Don't forget to carefully match volume levels between sources when comparing, preferably with a meter, because whichever you set the volume to loudest may sound most "detailed" or "powerful" or insert-listener-impression-here because of the way hearing works.

 

[discoprince]

Thank you. Both of you helped. I did a bit of reading about amplification and harmonic distortion and I can make some sense of it now. It is not necessarily about the amount of power, depending on how much power you need regarding type of headphones and listening levels, but more about the quality of power.

For my ears, there was an audible difference using the theorem 720 when compared to using my little fiio amp (using hd700).
There wasn't, to my ears much of a difference between the theorem and a large desktop system I auditioned. There are many factors at play here, and I will stop getting wrapped up in specs and just find something I enjoy listening to.

 

[SilverEars]

I've seen DAPs measured to veryfy the max power spec'd.  They use a 32ohm resistor and check for 1% THD which is for clipping since SS amps max power limit is where the distortion is significant or where it clips.  You see it on tyll's amp measurements where you see the distortions rise vertically. That's the max.  Of course it's different for load values as shown on here.
 
 http://www.innerfidelity.com/images/AllAmpGraphs.pdf

 

[castleofargh]

specs are all over the place, I find this "index" to give an idea of the problem at hand with manufacturer's specs in general: http://www.rane.com/pdf/ranenotes/Audio_Specifications.pdf

 

[discoprince]

  specs are all over the place, I find this "index" to give an idea of the problem at hand with manufacturer's specs in general: http://www.rane.com/pdf/ranenotes/Audio_Specifications.pdf

Excellent read. Thanks for that.