That’s what it is then, the 600ohm might be the max it can do, I hear the sweet spot for the Darkvoice is 280 ohms… So maybe why the 6XX is top tier headphone for this amp. I use a DT770 250ohm with the Darkvoice… sounds amazing and plenty loud. A 7236 will probably help out with the 600ohm headphones better
Okay. But like i said, it works fine, i dont need to turn the volume up to 3 ´o clock. 12 o´clock is okay with both headphones volume wise. For now i will stick with the new RCA tube and see if i can hear a difference 
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Nice photo, congrats on the RCA. 
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Listening the whole evening now and it sounds awesome. Can´t say much more, besides that it sounds better to me. Switching back and forth between my 6XX and my 880s and i feel this is pure musical bliss at the moment. Enjoying it very much 
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Something special about old time technology shot in black and white. 
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This is a reply I got from a dealer in Canada. Does anything jump out to the veteran tube collectors?
A pair of NIB Sovtek 6sn7 GT / 6H8C (Russian) Black base
6sn7 GTA singles:
-rogers black plate
6sn7 GTB singles:
-ge crome plates (usa)
-philips (japan)
-rogers black plate L6
-realistic lifetime (japan)
-sylvania PW
-Tung-Sol black plate (usa)
These are all $25.00 each in Canuck bucks.
The pair of Russian Foton s (first listing) and Tung Sol ( last listing) are nice .
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So, the new ones would be better than all the NOS?
I’m not familiar with those listed in the middle, not a big fan of anything from Japan.
I am not familair with them either. I contacted the seller again and he said the top pair was new and everything else was NOS.
I also contacted VIVATubes and they have hundreds of 6SN7’s ranging from the “Wow, that’s cheap!” up to the “How much???” His response seemed a bit odd to me: “We normally recommend new tubes to work in newer amps.” Maybe because I was asking about his MANY affordable 6SN7’s.
I am tempted to buy four of five of the Canadian seller’s NOS and see what happens. 
So i had bought an 6SN7GTB copper coin first, which was actually terrible. It sounded super metallic, like banging sticks on metal sometimes. Really weird.
Than i replaced it with the new production Tung Sol 6SN7GTB. 200 hours of burn in didnt kill the left channel humming, it was still there. Sound was ok.
But honestly the best purchase was the 1950s (somewhere in the 50s) 6SN7GTA from sylvania. It was only 25€, so the same as the other ones i tried in definetly sounds so much better than the other ones. Very lush sound, love it.
Im not the tube guru, but thats my experience…
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Check em out, heck yeah and let us know how they compare. Just don’t get the GE!
That’s correct, tubes in the lower 50’s are the creme de la creme… nice find.
Yeah, the early to mid 1950’s Sylvania 6SN7GTA’s are really great bang-for-the-buck tubes and really present that lush tube-y sound that many associate with tube amps. T-plate Sylvania 6SN7GT/VT-231’s from the 1940-early 1950’s are great too, but are a little pricier. Sometimes though, one may drop below $30 on ebay. I know some people like them, but I thought the flat-plate Sylvania 6SN7GT’s were mediocre compared to the t-plate 6SN7GT’s. Other 6SN7GT’s to be on the look out for are RCA grey-glass 6SN7GT (the earlier the better) and Tung-Sol 6SN7GT (mouse-ears). The RCA grey-glass tubes are known for their concert-hall soundstage and I think that they are lush as well (been a long time since I popped one into my DV336). Likewise for the Tung-Sol 6SN7GT. I remembered that I liked them but forgot how they sounded, lol.
As for 6SN7GTB’s, I tried Sylvania’s and Tung-Sols and was not too impressed with them when compared to the one’s above. Still, they are both better than the stock tube.
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I ended up ordering seven:
6sn7 GTA singles:
-rogers black plate
6sn7 GTB singles:
-ge crome plates (usa)
-philips (japan)
-rogers black plate L6
-realistic lifetime (japan)
-sylvania PW
-Tung-Sol black plate (usa)
It was buy six, get one free. Total = $150.00, shipped
Of course my amp won’t be here until probably mid to late October. 
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Started to roll 6sn7 equivalent tubes awhile back, the dual 6J5 series of tubes are remarkable. The 6J5 are SINGLE triode tubes, unlike the DUAL triode setup the 6SN7 tubes have. for the same output of one 6SN7 tube you’d need/want a dual setup of the 6J5. (same as 6J5G) Easy to do with a dual 6J5 to 6SN7 adapter. The sound of these tubes and for the price you can grab these for, marvel the triple digit priced 6SN7 tubes. I’ve fallen into the rabbit hole of the 6J5 world… Now get this… THERE"S 6J5 EQUIVELENT TUBES!!! Right when I’ve reached optimum Nirvana with the 6J5… the loctal 7A4 drop into my lap. The 7A4 is the loctal based tube version of the octal based 6J5 (similar comparisons are the 7N7 loctal the same as the octal 6sn7) Loctal tubes have them short thin metal pins that stick out of the bottom, not the regular pins as octal tubes. So to roll these 7a4 tubes…I had to get another adapter. I got lucky and found some really cheap single 7a4 to 6j5 adapters…(to plug into my dual 6j5 to 6sn7 adapter) Hiding from the adapter police!! And wow… I mean wow… I’m a huge fan of these little gems…you can find them as low as $5 and they whack a wallop as for as pure music enjoyment goes. I like em over the more expensive GEC L63 (YES ANOTHER EQUEVELNT TUBE) The GEC remind me of other tubes I already have. It’s nice just not giving me the wow factor as these cheap little 7A4 did… The 7a4 sound like TUBES. That’s why I like emso much, the GEC L63 is very clean and no tube bloom here. If you like that over a tubey bloom sound (like the 7A4)…GECL63 is your pair.
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Ohhh, I am so happy i did not sell my DV off. hehe so many GREAT ideas and flavor options here. Great post @JKDjEdi !!! 
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With the Dark Voice I got about a month ago, I can only use a RCA 6080 and a Westinghouse Getter D 6sn7GTB. Any other tube or tube combination causes buzzing. I know of the Fitz mod to fix this but I don’t have any soldering experience. The Westinghouse tube is amazing though, so it’s not a big deal.
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Alternatively, you can burn-in the buzzing tube for 24-72hrs to remove the buzzing. If you do decide to burn-in the buzzing tube, be sure to leave the power tube 6AS7G socket empty in order to keep the amp cool during this process.
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I don’t think burn-in is the issue here. I have a Lyr 3 and the tubes are just fine on that. Even tubes I have used for more then 100 hours still buzz. The Westinghouse are the only tubes that don’t buzz.