Sold them. Since I have been listening to my AKG K340 for a long time, highs and upper middles (which are responsible for the naturalism of sound, the sense of presence during the performance of music) which are ideal, I still could not get used to this mishmash on highs, which is given by 580s...

Hi, as I can find not - 6J2P gives almost twice less power than 6J1P

I just cut a pair of rubber rings from a pair of condoms - very good quality of rubber/silicone and exact size. :)

As I know, not. the presence of a rhombus sign indicates military suitability. I'm not a big tubeworm, as I can see 6H13C is the Russian and 6N5P - Chines made What is the question?

Hi Mordy, You can easily find out some Russian tubes with OTK sign, but without <> rhombus sign - this is the tubes made for civil purposes only, or maybe the tubes which did not pass hard parameters military QC. This does not mean that they are "bad" or "worse" than the diamond tubes, maybe...

from my post at diyAudio forum: "As I know: "OTK" - sign of QC department, means that standard quality control passed. In the Soviet times ANY PRODUCT of ANY factory or other production MUST BE checked by "OTK" department - it was guaranty to civil buyers/users that this device is good and safe...

Someone may have written about this before, but however I will clarify what I know from here, on this side of the iron curtain: 1) Inside the tubes is NOT a gold grid (!!!). An alloy of gold and platinum is applied to the grid. In the amount of 0.259 mg. Sorry guys that so not much :) 2) The...

I have not yet had the opportunity to compare directly, but I think there "may be" difference (thinking logically there should be some differences in construction, for example - cathode to provide 5,000 working hours (-EV version) instead of 2000 (original 6J1p)) - your ears will tell you exactly :)

Yes they are the "same" by the overall construction, but there are some differences: The prefixes on the Russian tubes means (Google translate): V (Cyrillic "B") - tubes of increased reliability and mechanical strength; D (Cyrillic "Д") - tubes of special durability with guaranteed operating...

takato14 Thank you! First picture - membrane grids difference - I know, but second pic, about bracket - it's new for me. Great pics - thanks 

I agree! 

takato14 Thank you! Great and useful info.   whether it is possible to distinguish visually from a photograph? On eBay pics for example? Thanks

Some years ago i picked them up on eBay in unused "in a box" condition. A couple of months ago i was in need money and think to sell them, but then I try them to check before selling how it's working ...WoW!!! They sounds so goood!  So now i'm happy owner of a pair this great vintage ears "from...