I've been having a great time comparing all the tubes in the EF2A and I still have a lot more testing to go before the tubes are fully burnt in.
But here's what I can say about my first impressions of all 4 sets that I own.
Stock Chinese Tubes:
These tubes were sent to me pre-burnt and sound better than I expected. The tubes have a good amount of low end but the highs are little piercing. Even though they performed better than expected, these are my last choice.
These tubes were also sent to me pre-burnt so I cannot say how they compare to being used right out of the box. What I did notice, however, comparing directly to the Chinese tubes is that the Raytheons have a deeper lower end and a much more pleasing high-end. Not nearly as shrill as the Chinese tubes. A nice improvement.
The Hytron Tubes sound about on-par with the Raytheon tubes at the moment and I hope to hear a noticeable improvement once they get some more use. But all-in-all they are pleasing across the whole audio spectrum with a good amount of impact. Very happy so far with these tubes as well.
This is the stand-out tube for me so far. Right out of the box it sounded AMAZING! Tons of low end, crystal clear mids and highs and absolutely no distortion or hiss at any volume. I was really surprised to hear such a dramatic difference compared to the other 3 sets that I have, but the Tung-Sol's just make my music sound more "powerful". I've heard good things about the Tung-Sol's and I bought them on a whim, and I'm very glad that I did! If they continue to sound better, I can't see myself changing out these tubes!
MORE COMMENTS TO COME (after further testing)
Now I'm very curious about Tung-Sol tubes. If anyone has experience with this brand of tube I would like to hear your thoughts on how they compare to other tubes you've heard from other manufacturers. I find them to be a stellar sounding tube so far!