[Richard941]

Stax Basic headphones 
Original SRM-Xh driver unit
SRM-T1 valve driver unit
 

A few years ago, I had to shorten one of the cables to the headphones because it was broken.
Recently I had to repeat the process, but the rectangular part (similar to the one shown in the Internet photo) came off. My fault - I got it too hot.
 
I took a risk and soldered the wire without the rectangular part and connected the cheaper driver unit. It works OK and I cannot hear any difference, but I don't want to risk connecting the valve driver unit.
 
What is this rectangular part?
Is it OK to solder the cable without it? Will this damage the headphones or driver unit?
 
 
Thanks for your help.

 

[edstrelow]

Since no-one wants to take this on let me start.  Each Stax driver has, I believe, 3 contacts, the bias charge  to the diaphragm and the signal to each of the plates. ( Possibly someone will correct this if I am wrong.)  I am assuming that the rectangular part is a contact to one of these, although which I cannot tell.  Possible a better picture of the contacts would help.  If you are able to solder to some kind of stub contact and the sound is unchanged,  then you would have seem to have successfully repaired the unit.  If any of the contacts was dead that should produce an obvious loss of volume to the driver. 

 

[Richard941]

Thanks very much for your reply and for your idea of photographing the part:
 

 
The part is roughly 6mm x 3mm.
It has solder at each end.
Originally, the middle wire of the 3 core cable was soldered to the one end, and the other end was connected to the metal plate - connected to the diaphragm?
The part seems to have been "glued" to the metal plate - I cannot see any solder or contacts underneath.
 
Is it an electronic component? If it isn't - why is it there?
Thanks for your help.

 

[edstrelow]

What I was getting at was what  the driver looks like where you soldered the wires.  I can't figure out what is there and what you soldered the wire to.   Also  what is the headphone model?  I assume  this is a Lambda pro but I don't know the model, there are about  a dozen or more Lambda pro models. 
 
I am guessing that the metal tab was connected to part of the electrostatic driver so that if a new cable was needed, you would not have to get  a hot soldering iron too close to the driver where it might damage the driver. 

 

[Richard941]

Thanks for the quick reply.
The headphones are Lambda Basic. I bought them (used) several years ago, so I am not exactly sure when they were made. They came with the SRM-Xh driver unit. Here's an Internet photo:

 
Photographs of the right (undamaged) connections:

 

 
A - Metal
B - "Plastic" 
C - Rectangular part
 
Under B - I cannot see any electrical connection between the two ends of part C - just "plastic" - difficult to show on a photo.
The signal or bias seems to have to pass through the rectangular part, but a continuity tester shows no continuity between the two ends of part C. I assume the high bias voltage can pass through it.

 

[Richard941]

I think I've found a partial answer. 
Part C looks like these - Surface Mount Resistors:

 
Here are some details:
http://www.learnabout-electronics.org/Resistors/resistors_07.php
 
 
Strange that wiring the left headphone without the resistor gives no audible difference in tone or balance. I'll have another listen.
I wonder whether I'll be able to "glue" Part C back on to B, and then resolder the two ends.

 

[edstrelow]

What you say sounds right, it just doesn't look right as to how the "resistor" is wired in, presumably in series.