Hi guys.... I said I would make a few comments on 7N7's.
I ordered 3 pairs from Vintage tube services:
Philco tall bottles
Sylvania red/green tops
RCA green dots
All of them are NOS mid 40's to early 50's tubes I am led to believe, costing $60-$70 for a matched and tested pair. I also had a pair of non-identifiable 7N7's on loan from Phil which are probably some well used Sylvania's..... I believe that "most" of the 7N7's were re-branded Sylvania's...? I used the Taiwanese adapters again borrowed from Phil.... 7N7 to 6cg7 type which I believe are currently still out of stock? If someone knows another source for these, please let me know. I use the EML rectifier.
I compared the 7N7's to a nice pair of twice the cost NOS green dot Sylvania 6SN7's.... I don't have a pair of TS round plates for comparison.
The Philco's were the first I tried and they sounded beautiful compared to the 6SN7's.... more detail, better imaging with very specific image placement and loads of bass and general body... image density. A very sweet sounding tube.
The Sylvania's were next and actually sounded VERY similar to the Philco's but with an even slightly sweeter mid-range. The rest of the spectrum was good, but didn't have that tiny extra little bit of magic the Philco's injected.... couldn't put my finger on it and would have been very pleased with them if I hadn't heard the Philco's first.
The RCA's sounded a little different.... bigger soundstage and a lighter, airyer presentation. More detail than the previous tubes, but not so much weight, although very tight and precise bass. Although there's a little more detail than the Philco's, the image placement isn't quite so specific.
All in all, I'm keeping the RCA's and the Philco tall bottles as they are different enough to be useful in different situations/music/systems. The Philco's are great for rock and the RCA's good for acoustic and classical etc.
So.... my experience with the 7N7 tube, including Phil's unidentified 7N7's, is I prefer it to the good quality 6SN7 I had in comparison.... still don't know how they compare to the TS roundplates. Andy at tube services believed the average 7N7 "may" sound better than the average 6SN7 because of better vacuum and a more direct pin connection...? If the "Holy Grail" Tungsol roundplates are unavailable for whatever reason, the 7N7 may be a good budget substitute for some...?
Cheers,
Mark