[moogoob]

There's an interesting thread in the same (sound science) subforum that you all may find interesting.

http://www.head-fi.org/forums/f133/h...ne-abx-429619/

It seems that they discovered measurable differences between dedicated amps and receivers- at least the ones they tested. At the very least, high-impedance low-sensitivity headphones were affected the most measurably by being inappropriately amped, if I understand their findings correctly.

 

[Pio2001]

Exactly, and we validated the audibility of the frequency response distortion with a double blind listening test against the dedicated headphone amplifier. (ABX 8/8, left and right levels matched within 0.1 dB).

 

[odigg]

Quote:

Originally Posted by moogoob /img/forum/go_quote.gif It seems that they discovered measurable differences between dedicated amps and receivers- at least the ones they tested. At the very least, high-impedance low-sensitivity headphones were affected the most measurably by being inappropriately amped, if I understand their findings correctly.

At least one explanation for this is well known. Many speaker amps power the headphone jacks using resistors off the main amp circuit (I know this because I emailed a lot of amp manufacturers and asked them). This means the output impedance of the headphone jack is very high. This results in measurable bass hump with low impedance headphones and even high impedance headphones as is seen in the link you gave.

Still, I'm glad a listening test has been done. At least somebody is doing them, although it's a given that differences will be heard if the FR graphs between eqiupment are very different.

Notice with the Marc2 sound card the variations in the FR graphs are much smaller than the receivers. One of the conclusions is "That the soundcard seemed to be able to output higher levels with similar quality. "

That's specifically why I've asked people to do a controlled test of plugging their headphone in straight into their sound card versus a dedicated headphone amp. It's my understanding that many sound cards have a fairly low output impedance and so this should not cause the bass hump you see in the speaker amps.

**edit**

I had only glanced through that thread linked by moogoob and Pio2001 and I'm somewhat confused by the results as they go against the tests I've done for my own interest. That doesn't mean either of us is right or wrong, just that I've got something new to learn about!

If anything, it only reinforces (at least to myself) my stance that people should be doing volume controlled tests on their own eqiupment to see if they can hear a difference.