AH ok I understand what you are asking now. The reason for the two pins are one large one for ground, and a smaller one for signal. These are inserted into the headphone and a small spring within the cup conducts the signal and sends it along some very thin wires to the driver.

Wouldn't surprise me. HD800 doesn't scale much if any on the ZDSE. You should get a ZD Super sometime or have it upgraded to a Super. I hated the ZDSE and made sure to tell Craig every chance I got. Unfortunately, I can't do that anymore. 

Unfortunately EC won't re-work my current ZD SE to a Super level.  I'm trying to find out if they'll send me the parts so I can do the upgrade myself but I'm pretty sure that will be a big no.  I've only had it for a few months so it kind of sucks that I caught the tail end of the outgoing model with no option but to sell and re-buy if I want the new one.  Now that the new one is getting rave reviews, I'm sure that won't help the secondary market for the old one.  Bad luck and timing.  I can understand why EC wouldn't want to re-work old models as it would probably be a process change for them.  All of that aside, I think the non-Super ZD SE does wonders with the HD650's which is why I bought it in the first place.  The sound stage and the treble energy in particular.  No other headphone has continued to scale as well as the HD650's.  Going from a portable amp/dac, to OTLs (crack and La Figaro 339) and then to ZD SE, the 650's just keep on giving. 

Unfortunately EC won't re-work my current ZD SE to a Super level.

If you got yours a few months ago, you might have some of the changes already. There have seen some revisions and tweaks over the span of some time. I would say if you like the tonal balance of your current setup with your existing tubes, keep it as it is.

My "high end" in headphones started with the HD580 paired with the Musical Fidelity X-cans in 1995. They were then TOTL dynamic and the Jubilee edition was released later in that year. I have always had fond recollections of those headphones and I recently decided to pick up a pair of HD600, somewhat out of curiosity and somewhat out of nostalgia.

I was a little disappointed in truth, the memory far outlived the actual performance. Either my expectations were unrealistic or my ears have become so attuned to planar attributes but they sounded very mediocre of any number of amps I tried them on. It is not that I think they are awful but just not as good as most any of my other headphones. Unlike Purrin, I have sold my musical soul to the planar world. I can enjoy dynamic headphones for a short period but I most always end up looking for microdetail which I find in the planars but not so much in the dynamics. The HD800 behaves more like a center pinned planar than a dynamic , or more appropriately, center pinned planars behave more like a ring radiator. either way, I do not think of the HD800 as a typical dynamic headphone.

My intent had been to try and mod them as I was able to give new life to my K501's . There is hope but thus far the 600's have not shown me the great promise of a modern TOTL killer.

..dB