[Shahter]

Output impedance of phone jacks on amplifiers,receivers,cd's ets. How this parameter does affect the sound of headphones ?

For example the headphone output on mine Nad C352 has 240 ohm ,and my DT880 sounds pretty well with it ( on dedicated amp it's better of course ). But any headphone with lower impedance , sounds not so good on NAD .

Some explanation are welcome !

 

[Carl]

Quote:

Originally Posted by Shahter /img/forum/go_quote.gif Output impedance of phone jacks on amplifiers,receivers,cd's ets. How this parameter does affect the sound of headphones ? For example the headphone output on mine Nad C352 has 240 ohm ,and my DT880 sounds pretty well with it ( on dedicated amp it's better of course ). But any headphone with lower impedance , sounds not so good on NAD . Some explanation are welcome !

Impedance doesn't affect sound, impedance mismatches do. The effect is similar to the clutch on a car, transmitting power between two things. If the power can't be transmitted properly or the efficiency of the transfer changes with frequency, then you get an effect on sound quality.

 

[Shahter]

Sorry for not correct statement. I know that this is not affect sound directly . I just want to know is it possible to understand from that how some phones can match or mismatch specific equipment.

 

[Awk.Pine]

Two things: changes in frequency response due to changes in impedance are magnified by increased output impedance. This is the same as with loudspeakers. See this article at Transcendent Sound. In my understanding, matching impedances is important for power transmission--eg, power lines--but we don't care about electrical efficiency in audiophilia: we're okay with having lots of loss, aka heat, so long as what electricity does pass is everything we want and nothing we don't.

The second is sensitivity. Speakers don't vary much: bookshelf speakers are usually about 84-90 dB/mW. Headphones, on the other hand, range from, oh, 95-115 dB/mW. A difference of 6 dB between speakers requires twice as much voltage and four times as much current. A difference of 20 dB between headphones, however, requires 10 times as much voltage and 100 times as much current. Headphone amps need to produce (a) very low voltage noise, in order to remain silent on high sensitivity phones, and (b) high voltage, in order to push low sensitivity phones. Put together, then, the electrical noise floor needs to be much lower in headphone amps, relative to maximum output, than in speaker amps. Compromise is unavoidable, and many headphone amplifiers favor high voltage accuracy over low voltage noise.

I'm still trying to figure out a way to cheaply, but cleanly, power my 13-ohm IEMs.

 

[rockbottom]

Nicely put, Carl, good analogy.

 

[Shahter]

Thank you Carl and Awk.pine !