I've started on the tube rolling adventure with my 337 and so far have been pleased. I listened to it stock for a week or so and enjoyed getting to know the sound signature of this amp.
The first tubes I rolled in were a pair of NOS Tung Sol 5998's and I've been listening to them for about a week. I didn't detect a HUGE difference in between the 5998's and the stock power tubes, but te 5998's did have a slightly blacker background and I believe added a little more space around vocals and instruments. I got them for about 60 bucks shipped from Antique Electronic Supply (per Skylab's rec) and believe them to be worth that. I would have been disappointed had I paid the 120+ that many dealers are charging for these tubes because I don't think they make $120 worth of improvement. I still have some RCA 6AS7Gs that I bought from Skylab that I haven't tried yet, but will soon.
The next tubes in (still with the 5998's in the power slot) were some 6SJ7GT Tung Sol mesh plates (again per Skylab's rec) are a little problematic. They've only been in for 30 minutes, but there is a definite hum that was not there when running the stock Chinese driver tubes. I'm hoping this will disappear with some use. The hum does not change when I switch tubes, unplug cans, unplug source, turn up/down voume, etc. It is a constant hum in the background that is present with nothing connected and the volume turned all the way down. Its still too early to make any comments on the sound of this tube, especially with the hum.
The next set I tried were some of the red RCA 5693's and straight out of the box they were dead silent and really sounded great. The add a very pleasent richness/harmonic to the midbass/midrange spectrum. I especially notice this on accoustic tracks (James Taylor's One Man Band CD in particular) and on orchastral tracks. The tubes really add some nice body and rich flavor to James' Baritone voice and Yo Yo Ma's Cello. These tubes only have about 30 minutes on them as well so we'll see what happens to them with a few hours of use. Overall, I think these red RCA's are a great tube for this amp. They can be had for SUPER cheap and everyone seems to sell them. They seem to go in lots of 5-10 on ebay all the time.
My experience with tube rolling in the 337 helps to solidify my feelings on tube rolling. Nice tubes can help refine the sound you already have, but if you don't like the stock sound, I don't think any amount of tube rolling will change that. I also think I'm going to have to cap my my upper limit on tube spending. The 337 tubes are not a lot of money (which I love) but I really don't think I could bring myself to spend $300, $400, even $500 on sometimes a single tube.
Regardless, may the tube rolling adventure continue!
And of course, we use different headphones as well.
