Beyer DT770 600 ohm recable mod
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rbc3

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I'm in the process of adding mini XLR jacks, one in each can, to my DT770 600 ohm.  The intent is that I can then use the high end cables I purchased for my Audeze LCD2s interchangeably with the DT770.  In all the Beyer recable mod threads and guides I can find, none of the photos show these resistors (see below) attached to the drivers.  Since I'm wiring left and right channel in to separate dedicated XLR plugs with positive and negative leads per can, do I need these resistors?  What are people's thoughts?  Leave them on or remove them?  I'm not an expert, but my best guess is that they're on there because the negative lead in a 1/4" phono cable is shared by left and right channels.  Since I'm going to separate the negative leads in the XLR jacks, I don't think I need these resistors.
 
Any help is appreciated!
 
-Robert
 

 
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rbc3

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As a followup note, I just wired a driver in to the mini XLR and plugged it in to my Audeze cable and in to my Schiit Lyr amp.  It works fine with the resistors, so I'm inclined to leave them on unless someone can provide a good argument as to why I should remove them.  I just can't figure out why my drivers have resistors and none of the other photos of Beyer DT drivers online have them.
 
-Robert
 
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rbc3

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Well shut my mouth!  Upon closer inspection what I called "resistors" are actually a pair of 85C Zener diodes.  When searching for diode use on Beyer drivers I found some threads discussing them as a voltage protection circuit that doesn't affect sound.  Apparently these diodes are found more commonly on the higher impedance Beyer cans.  So maybe the reason why most of the recable DIY mod threads don't show them is because the mods were done on low impedance Beyers.
 
-Robert
 
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Lorspeaker

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can u post a series of stepbystep fotos of how u get this done?
and where the soldering is done :p
 
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rbc3

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Sure.  I'll take snaps and start a new thread.  I'm basically following this guide:
 
http://www.diyaudioblog.com/2011/12/recabling-pair-of-beyerdynamic-dt880.html
 
The only difference being that I'm getting rid of the single side cable connection standard on all Beyers and replacing with two mini XLR jacks, one in each can.  I'm wiring the XLR jacks to the driver in each can and there will no longer be a cable running through the headband to the other can.
 
The guide for making an Audeze style cable with two mini XLR plugs that will work with the mod I'm doing can be found here:
 
http://www.diyaudioblog.com/2011/11/custom-audeze-balanced-headphone-cable.html
 
The Audeze cable guide is also a good source for determining the correct positive and negative pinouts for the mini XLR jacks in the cans of the Beyers.
 
I figured out left and right positive and negative on the Beyer drivers by using a voltmeter with the original cable.  On a 1/4" phono plug, the tip is left positive, the inner ring is right positive, and the base ring is ground.
 
The only tricky part I've run in to is that I'll have to grind down the back of the XLR jack in the inside of the Beyer can so that the drivers fit back in to the can.  It won't look pretty when I'm done with it, but it's on the inside of the can.  So once everything is back together nobody will be the wiser.
 
-Robert
 
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rbc3

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Whew, I finally finished my mod. It took me long enough!  Here's a quick breakdown of my mod.
 
Step 1 - breakdown
I disassembled the headphones, unscrewed the plastic cups from the headband, opened up the cups, removed the drivers from the cups, removed all the current cabling, and marked the left and right positive and negative on each driver (see photo above).  
 
Step 2 - installation of new connectors
I bought a pair of Rean (Neutrik) Tiny 4-pole XLR chassis mount connectors, drilled holes in the bottom of the cups that fit the outer diameter of the chassis mount connectors, and installed them.  The tricky part in the installation of the chassis mount Tiny XLR connectors were 1) I needed to find some spacers so that the pins didn't interfere with the drivers when installed in the cups, and 2) I needed to shave off part of the chassis mount connectors so the drivers sat flush in the cups.  Once I had the XLR connectors mounted in the cups in the direction I wanted them, I soldered the tightening nuts to the XLR connectors (to keep from coming loose) and used a Dremel with a metal saw attachment to cut out a section of the connectors so that the drivers would sit flush in the cups.  Then it was a matter of soldering some wire to the pins of the XLR connectors and then to the drivers (see included photo).  Look for Audeze cable mod online for diagrams of the positive and negative pins.
 
Step 3 - reassembly
I popped the drivers in, replaced the pads, and screwed the cups back to the headband.
 
There are some minor details I left out to keep this from being too wordy like shrink tubing on the pins of the XLR connectors so they don't touch something and short.  I also decided to spray the plastic cups matte white for fun.  I think they turned out pretty good!  For spraying plastic, follow good paint prep practice... sand, clean, prime (even if your paint says it includes primer use a separate prime coat), and let the paint cure for at least a week before assembling (even if your pain says dry to touch in 1 hour and ready in 24 hours).
 
I can't speak to any sonic differences because I had them apart for over six months!  I don't have a balanced amp that can drive them yet either.  They sound great with a stock Audeze single ended cable and my Valhalla.  I'm building a Bottlehead Mainline that I know will be a fun combo.  So far the DT770 600ohm is the best closed can I've heard.  Although I've not heard the top end Fostex, Denon, or Audeze closed cans.
 

 

 
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Lorspeaker

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i am using alphapads on the dt770/600 ....
very interestg effect..as if i am hearing thru the pads in high clarity..
the pads sorta disappeared.
 
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