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Need help with cable for AKG K240

post #1 of 14
Thread Starter 

Hi, I posted this on the cable forum but the thread got buried with no replies... hoping I'll have better luck here.

 

The cable for my AKG K240 Studio headphones crapped out, so I bought a female mini XLR plug to build a new one. I used this document from AKG support as a guide - if you look at page 5 there are schematics for the cables.

 

The issue I'm having is, instead of getting stereo audio, now I'm getting a mono sum of both channels with one of them inverted (so anything that is at the same level on both channels cancels out). To test this, I plugged them into my receiver and played with the balance knob. Even with the balance knob turned all the way to R or L, the sound is going to both capsules. When it's dead center, there is some phase cancellation.

 

I've tested all my connections with a continuity tester and they are all correct and nothing is shorting, so what could be causing this?

 

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post #2 of 14
Thread Starter 

Nobody?

post #3 of 14

Might it be the wire you're using? i just used a rather cheap wire to try and recable some iems i had lying around I'm getting mono sound as well with them.

post #4 of 14
Thread Starter 
Quote:
Originally Posted by Netforce View Post

Might it be the wire you're using? i just used a rather cheap wire to try and recable some iems i had lying around I'm getting mono sound as well with them.

That was one thing I suspected in the beginning, which is why I tested each wire with a continuity tester, and also tested them for shorts. There are no shorts and continuity is good, so I don't think the wire is the problem?

post #5 of 14

Definitely sounds like you've got the ground swapped with one of the signal pins.

post #6 of 14
Quote:
Originally Posted by DingoSmuggler View Post

Definitely sounds like you've got the ground swapped with one of the signal pins.

 

This.

 

What does the ohm-meter say when you measure the following on the TRS plug:

Tip to Ring

Tip to sleeve

Sleeve to ring?


Edited by nikongod - 4/3/13 at 11:23am
post #7 of 14

I am actually in the process of doing the same to my k240mkii. I saw on another thread that akg might use a nonstandard way of wiring. This is the link to the post http://www.head-fi.org/t/648464/recabling-my-headphones

I am still trying to understand how to wire them but i hope this helps you

post #8 of 14

Are you trying to balance these or just recable? or redo the housing? I'm not sure what type of cable you are building

post #9 of 14
Thread Starter 
Quote:
Originally Posted by JBal4 View Post

I am actually in the process of doing the same to my k240mkii. I saw on another thread that akg might use a nonstandard way of wiring. This is the link to the post http://www.head-fi.org/t/648464/recabling-my-headphones

I am still trying to understand how to wire them but i hope this helps you

 

The schematic I posted (which I got from AKG and which I followed for my cable) is the same as the pinouts on your thread. 1 is ground, 2 is right and 3 is left. That's what I did, but I'm having the problem I described in the first post.

 

Quote:
Originally Posted by DutchGFX View Post

Are you trying to balance these or just recable? or redo the housing? I'm not sure what type of cable you are building

Just recabling. The original cable died on me. Building a bog-standard 3-pin mini-xlr  to trs cable.

post #10 of 14
Quote:
Originally Posted by antiuser View Post

The schematic I posted (which I got from AKG and which I followed for my cable) is the same as the pinouts on your thread. 1 is ground, 2 is right and 3 is left. That's what I did, but I'm having the problem I described in the first post.

Just recabling. The original cable died on me. Building a bog-standard 3-pin mini-xlr  to trs cable.

Ohhh gotchaaa. I'll use my MM later to test which pin goes to where. I think 1 3 are signal 2 ground but not sure, don't take my word on it
post #11 of 14
Quote:
Originally Posted by nikongod View Post

 

What does the ohm-meter say when you measure the following on the TRS plug:

Tip to Ring

Tip to sleeve

Sleeve to ring?

 

Why haven't you answered this question? 

post #12 of 14

Is it possible that your wiring in the headphones got damaged when your cable got broke? I just finished a mini-xlr to 3.5mm cable for my k240 mkii using the same wire setup and it worked perfectly.

 

pin 1 - sleeve - ground

pin 2 - ring - right

pin 3 - tip - left

post #13 of 14
To build on that, a broken cable seams fishy. What exactly in the cable broke?

Test your connections with a multimeter to ensure they are connected and there are no shorts.

Cut and strip both ends of a small wire, and stick it into the holes in the xlr, and put the other end on the pieces of the TRS
post #14 of 14
Thread Starter 

Sorry to revive an old thread, but I got sidetracked by real life and only now have time to try and fix my headphones again.

 
Quote:
Originally Posted by nikongod View Post

 

This.

 

What does the ohm-meter say when you measure the following on the TRS plug:

Tip to Ring

Tip to sleeve

Sleeve to ring?

 

Tip to ring: 112 ohms (which funny enough is nearly exactly double the reading I should get, since each driver should read around 55 ohms.

Tip to sleeve and sleeve to ring: 0 ohms

 

And just to make sure it wasn't the cable, I measured it right at the connector on the phones. Same deal.

 

Quote:
Originally Posted by DutchGFX View Post

To build on that, a broken cable seams fishy. What exactly in the cable broke?

 

 

Well, here's where it got interesting. There was an intermittent connection near the XLR plug on the cable, which I confirmed by testing it exactly as you suggested. If I twisted or bent the cable a certain way, the circuit would complete, suggesting there was a frayed wire inside or maybe a bad connection inside the plug. So I just cut that end off, bought a new mini XLR plug and soldered it on.

 

Today I finally had time to sit down and take the headphones apart, since it became clear that the cable wasn't the culprit. Then I found my problem. Cold soldering at the factory? Anyway, I have the soldering iron warming up right now to fix it.

 

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