NA Blur said:
A typical audiophile would be shocked that anyone would consider such a thing . . .
Defining your use of "better" would help, but working with the general use of the word here is what I find in a good amp.
1.) Low harmonic distortion ( THD < .002 % )
This gives a nice clean signal without distorting the input waveform
2.) High signal to noise ratio ( SNR > 98dB )
This allows the noise floor to be low enough to prevent distortion and other adverse effects )
3.) Larger frequency response ( FR: 10Hz - 30kHz )
At minimum you want to include the entire human audible spectrum which is typically 20Hz - 20kHz, but I find the wider the FR is the better.
4.) Lower output impedance ( X < 5 Ohms )
Anything else higher can lead to, call it atypical, frequency response issues along with distortion
5.) Output power at 1Khz ( P > 250mW )
This is something I look at to make sure the amp can adequately drive the many types of headphones out there. Due to headphones having not only different impedances, but sensitivities as well, the higher the output power up to 1W the better. Any higher is just ridiculous and too much power for most practical use headphones.
Those are the 5 things I look for in the specs in determining a better amp. The next thing I do is check the physical design including how the power supply is implemented as well as functionality. The final test is to listen to it and compare it against what I already have.
Thanks to nick for cathing my typo.
So, let's take these ideas to their logical extreme. Consider the $20 Fiio E1, which is powered directly from an iPod as its power source.
Tech specs here: http://www.fiio.com.cn/product/index.aspx?ID=14&MenuID=020301
Question: Should the E1 drive the Audeze LCD2s adequately? (tech specs here http://audeze.com/audeze-lcd2-bamboo) (Certain audiophiles might call me a blasphemer just for asking . . . )
If Fiio is to be believed, then the E1 does fine in criteria 1, 2, and 3 from the quote above (harmonic distortion, signal to noise ratio, and frequency response).
Fiio doesn't tell us anything about the output impedance . . . but then again neither do most amp manufacturers.
As for power, the LCD2 has an efficiency of 91dB at 1mW and an impedance of 60 Ohms. Science tells me that power requirements multiply by 10 for every 10 decibel increase in sound, (i.e. if r = (decibels in excess of 91)/10, then power usage of LCD2 = 1 mW * 10^r ) and this is verified by the observation that the LCD 2 is rated for a maximum output of 133dB at 15 Watts. 133-91 = 42. 15 Watts = 1mW * 10^4.2 (approximately). A volume of 101dB is dangerously loud, so let's assume that we don't want to listen to music substantially louder than that. That would require a power usage of 1* 10^1 = 10 mW. The Fiio E1 is rated for 12 mW output at 300 ohm impedance and 100 mW output at 16 ohm impedance. The output at the 60 ohm impedance of the LCD 2 should be somewhere in between those, and at any rate, well above 10 mW.
So in conclusion, the Fiio E1 should drive the LCD2 just fine to volumes of over 100 dB, unless its unknown output impedance is too high or there is a problem with its physical design.
I really hope that's true, because I'd like to buy a pair of LCD 2s, and it would be great if I could amp them for $20. On the other hand, I have a suspicion that it's not true. The E1 is powered directly from an iPod -- it doesn't require any separate power source. Surely that should not be sufficient to power a massive headphone like the LCD2, at least according to popular wisdom. And yet the calculations in the previous paragraph show that it should, unless you want to go to volumes that would cause hearing loss very quickly.
I can see two possible types of problems with the line of reasoning I've expounded above:
1) NA Blur's criteria may be incomplete or incorrect, or I may be interpreting them incorrectly -- maybe the physical design part at the end is really important
2) Fiio or Audeze might be lying or mistaken about technical specifications
Anybody with a pair of LCD2s want to give it a try with the E1 and report back?
Or anyone want to point out what's wrong with my reasoning?
I am really puzzled by headphone amplifiers.
Edited by Norman314 - 6/18/12 at 1:42am