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impedance adaptor for headphones

post #1 of 23
Thread Starter 
Dumb question but help me out here, building a 75 ohm impedance adapter would require running a resister in line on both the left and right channels? Or does the resister connect the left and right channels?
post #2 of 23
You put a resistor in series with both left and right, yes. The channels do not connect to each other, and you leave the ground alone.
post #3 of 23
I asked a similar question via PM to balou and here's a great response:

"It's really simple. You just put two 75 ohm resistors in the cable, both in the left and right channel. You could do this directly at the plug - e.g. solder a resistor to right and left input, and then solder the left and right wire to the respective resistors.
Use metal film resistors - either buy a bunch (10 or so, thats most of the time the minimum quantity) of 1% resistors and match them with a multimeter, or buy 0.1% ones (minimum quantity often is 1, so you don't need to match and don't have any spares left)"


This is probably common knowledge but are you suppose to match resistors within a certain acceptable range ie: within 0.1% etc.? are 1% resistors matched within 1 %?

Also if you're making an adapter and the resistors don't match, are they pretty much useless for this puprose?

lastly, why metal over other materials ie: carbon film/etc.?

Cheers
post #4 of 23
Thread Starter 
Thank you Fitz and Bargy good info. Now the soldering begins
post #5 of 23
Forgive me if I am blanking out on this topic: Why do you want to raise the output impedance of the amp (or input impedance of the 'phones)?

F
post #6 of 23

Deleted.


Edited by labrat - 9/8/11 at 11:12am
post #7 of 23
I have one of these if someone wants one:

http://www.fixup.net/products/pktamp/xinaddon.htm

with XinFeed. I think I will put this up on the FS forum.

I will put some pictures into my gallery showing what it looks like shortly.

I just put this up in the FS forum.
post #8 of 23
What meg-ohm input resistance does one need to measure 1% resistors? What does the tolerance need to be of the multi tester?

Bob, a novice with basic electronics.
post #9 of 23
It won't really matter. Any multimeter will work.
post #10 of 23

Sorry for bringing an old thread to life but what is the power rating the resistors should have, 1w, 2w, 3w or even higher?

post #11 of 23
Quote:
Originally Posted by Hal Rockwell View Post

Sorry for bringing an old thread to life but what is the power rating the resistors should have, 1w, 2w, 3w or even higher?



12W. Maybe 15 if yer feeling frisky.

 

Seriously now, 1/8-1/4W. If you happen to like botique resistors, whatever the lowest power rating you can get that is more than 1/8W.


Edited by nikongod - 11/13/11 at 4:41pm
post #12 of 23

Etymotic uses 75ohm adapter to turn the ER-4PT into ER-4S which is considered to be better earphones. What the adapter does it to increases the overall impedance of the ER-4PT from 27ohm to about 100ohm. Will increasing the impedance to about 100ohm will improve the sound of any 32ohm Headphones?

post #13 of 23

I do not think the adapter alone, is responsible for the ER-4S's performance. Typically higher impedance in headphones is due to heavier magnets and voice coils for more damping and control. 

 

Increasing the resistance of a 32 ohm can will help control any low level noise in the background, and will help attenuate gain that is too high from an unruly amp, but that is about it. There should not be any qualitative difference in the sound quality since you are not changing the voice characteristics of the can itself (e.g. you are not really converting it from a 32 ohm to a 100 ohm headphone, you are just artificially increasing the load required)


Edited by liamstrain - 11/23/11 at 5:31am
post #14 of 23


Note that the frequency response and waterfall plots of  headphones can vary with output impedance.   This is one of those black art issues rarely talked about.  Older headphones were voiced for a 120 ohm output impedance.   Another example is Grado's bass  changes with resistors added in series.   In general  newer headphones have dropped the old 120ohm standard and are voiced for modern <1 ohm output.  Its an interesting subject to say the least and worthy of experiementation.
 

Quote:
Originally Posted by liamstrain View Post

I do not think the adapter alone, is responsible for the ER-4S's performance. Typically higher impedance in headphones is due to heavier magnets and voice coils for more damping and control. 

 

Increasing the resistance of a 32 ohm can will help control any low level noise in the background, and will help attenuate gain that is too high from an unruly amp, but that is about it. There should not be any qualitative difference in the sound quality since you are not changing the voice characteristics of the can itself (e.g. you are not really converting it from a 32 ohm to a 100 ohm headphone, you are just artificially increasing the load required)



 

post #15 of 23

So what do you say? Let the experiment begin!!! I just want to know what do you suggest on doing, make adapters that increase the impedance to 100 ohm or 120?

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