[balou]

Hi,
I wonder what impedance adapters are good for? I heard about the etymotic er4, of which one version just seems to have a 75 ohm resistor inline

and there are also some amps which have a switch to add some resistance.

So, could anybody explain to me what this is good for?

 

[mrarroyo]

Lets say you have an amp with a gain of 5 and a pair of very sensitive IEMs (1 kHz sensitivity: 108 dB @ 0.1V). Well if you also happen to have sensitive hearing plugging the IEMs to the amp will mean you probably will not be able to go past 8 o'clock because the sound will be too loud. This means you will have very little control over the volume since the movement of the volume pot will be from 7:30 to 8. By adding the resistance it will allow you to go to say 10 o'clock wich in effect allows for finer volume selection.

Also with some amps you can hear hiss/noise if the IEM is very reaveling. Using the in-line resistor prevents you from hearing this hiss/noise.

 

[balou]

does a 0.075k resistor really make such a change when the pot is 10k or 20k?
in this thread: http://www.head-fi.org/forums/showthread.php?t=221724 it is implicated that a 75 ohm resistor will somehow change the overall sound quality. but no further mentioning about the expected or perceived changes

in another thread, it is also mentioned that a 330ohm resistor improved bass performance of some sennheiser headphones.

about the noise... seems like this is similar to the optional output resistor in the cmoy amp. but here I also don't know why a resistor would shut off noise.

and for example the xin supermacro has different jumpers for setting gain and output impedance

could somebody explain this to me?

 

[Fitz]

Depending on the headphone's impedance curve, it'll usually either do little to nothing, or form a tilt eq that boosts the bass and lower midrange while attenuating the upper midrange and highs. It'll also lower the noise floor some if you have a particularly noisy output, because it attenuates the output and requires you to turn the volume up more to get the same level of output.

 

[procreate]

Quote:

Originally Posted by balou /img/forum/go_quote.gif and for example the xin supermacro has different jumpers for setting gain and output impedance could somebody explain this to me?

The gain switch changes the amplification factor.

The impedance switch puts a 75Ω resistor in series like the Etymotic ER•4 P to S adapter does. It's there specifically for those IEMs. Changing the impedance changes the frequency response curve of the connected headset.

 

[BushGuy]

ooops