[bigbargain]

Thanks Olaf for your very good energizer pics and explanation.  Perfect.
 
How do I remove the pads?  I have tried what looked obvious and looked at pics all over the web.  But mine seem to be on there really well or I just haven't figured out the trick.
 
And there even appears to be some kind of "skirt" around the perimeter that is pinched between the ear side of the assembly and the chrome ring.
 
HELP!!  Any help would be greatly appreciated.
 
Thanks.

 

[chetlanin]

Tip: Try to find a spot where the rubber edge possibly is slightly higher than the metal lip. Use your nails and fingers to pull the rubber aside and once you have made the slightest opening, insert a plastic knife to widen the opening. It will now easily and suddenly come off. ( Eventually use another plastic knife in addition).
I would generally avoid using metal tools, but if you do not manage to make the initial opening as described, insert a small and very sharp knife blade between the rubber and metal lip, keeping the knife edge firmly against the metal side of the joint. Then turn the blade slightly and insert a plastic knife in the slit. Good luck, Olaf
 

 

[bigbargain]

Thanks Olaf!!  It almost seems no one knows much about these cans.  I started a general restore thread here http://www.head-fi.org/t/670426/koss-esp-9-e-9-energizer-restore but no one has responded.  Ideally, I'd like to move this discussion to that thread, as I think this one is mis-labeled and I hope the other one will help others more.
 
Regardless THANK YOU very much. I will try your suggestion when I get off work.

 

[bigbargain]

So my energizer's internals are very different from the pic Olaf provided above.  See picture.
 
 
As you can see I rigged up a power cord and tried the phones. Still a near 100% imbalance with 95+% in the right ear.  And very distorted.
 
So i opened it up to begin looking for faults with my DMM and using the schematic Olaf provided.  No joy.  It looks like the bottom board is the same, but of course as is obvious the top one does't contain any transformers and is very different.
 
Looking at the schematic, it definitely describes a what is also in his pics so only partially applicable.  I will try to translate what I have tho the schematic I have.
 
yes I know about the high voltages and I work on tube amps so have developed some cautious habits.  But having a complete schematic around high voltage would be very helpful.  PLEASE  HELP if anyone has a schematic that matches mine it would be VERY helpful.
 
Thanks in advance.

 

[chetlanin]

Interesting. Then we know 3 versions of the energizer, and 2 or them are rather obviously modifications to the original design (the one with four transformers, seen in the schematics and in my picture), showing how they at Koss have tried to solve the problems with both (probably) magnetic distortion and hum. (But can one be sure that they upgraded the schematics officially?)
The third version?  In one of the Stax threads a version with only one “bias transformer”, and this is mounted as far away from the step-up transformers as possible!:

http://www.head-fi.org/t/223263/the-stax-thread-new/1305#post_2837197


Over to your problem with sound mostly from one cup. It should in principle be rather simple to find the cause, since the construction is very simple (despite the chaotic look) and since one channel is working as it should. The system consists of four parts, obviously: 1.The cans.2.The step-up transformers. 3.The high voltage supply  w the diode “ladder” etc. 4. The switches, leads and connecting points etc.

Electrically 2  and 3 are working independently of each other (Good for us).

A quick & simple check of the step-up transformer section to be able to eliminate it as a cause:
Send a test tone through the system, say a 1kHz sine wave or something. (Take out the plug and measure at the connector on the front of the box. The lower hole at 6 o’clock is the common point, it leads through a common lead to a stator in each cup. Put one probe in here. Go clockwise one step (to 9o’clock), this connects to the opposite stator in one of the cups, put the other probe in here. You should see a high AC voltage here. Then measure in the same way on the opposite side, at 3 o’clock, this is the stator in the other cup Good signal in both places, and we can eliminate the step-up transformers as the cause of the failure.

Next simple thing to do: Check if your unit has a common bias voltage supply (the two upper holes, btw). If so, the supply unit cannot be faulty, since one channel is working.  If your unit has a separate bias voltage supply for each cup, then see if you can switch the two upper leads to the connector (internally). If one of the bias supplies is faulty, it will now become clear.

Btw, how does it work in SE mode?
 

Cheers, Olaf.

(optimism in these situations is the main prerequisite!)
 

 

[johnhodg]

I know this thread is old but for anyone coming across it: I measured the bias voltage on my E9, it is 694 volts. I had a lot of weird problems at the beginning, it narrowed down to broken grounds between the E9 and the headphone and between the 2 earpieces. The amazing thing was that they worked, just not right. I have a 4th variation on the energizer, it is a single bias supply, but it looks different inside then the other 3. There is a good diagnostic routine in the Koss instruction book.
JH

 

[bigbargain]

Now no teasing. Can u share the instruction book?

 

[ri_toast]

If your getting hum from your esp9s I would suggest fixing the foam in the cups. I noticed some ground problem when i touched the headphone frame. After the foam was replaced and the cups were cleaned and dried the hum was gone..... silent now no matter what. The ear pads liquid filled? forget them, even NOS were the same; still flat. There is another Koss model pads that fit on backwards (swap L and R) perfect fit but a pita to put on just like the originals.
 
I admire your idea to use the Stax to power the phones. Personally I think replacing the Koss cable to something that wasn't romex like in flexibility would make the 9's much more pleasant. That and the massive clamp
 
My post with photos from a few years ago http://www.head-fi.org/t/408337/electrostatic-help-needed-koss-esp9s-updated
 
These cans now sit on a stand that I walk by daily and EVERY time I look at them I think I should hook them up and listen but I don't. I will someday.

 

[dramakon]

Would it be possible to drive a Stax Lambda with a Koss E.9 energizer? I'm really unfamiliar with what the voltage bias of headphones/energizers means. The Stax are 230v, whilst the Koss is 600v ?

 

[kevin gilmore]

pro bias, maybe, should be 580v, koss is 600v
 
low bias, definitely not, do not even try.

 

[dramakon]

I'd assume the sound would be less than ideal due to specific tunings on each brand