Originally Posted by KailM

5751s are not much lower gain than 12ax7s. Most of the time they're pretty close, actually. But they operate differently (and I'm not an expert on how tubes work). They just sound cleaner and richer; a little more "organic" to use a cliche term if you will. I love the way mine sounds with one of those in V1.

12at7s are definitely lower gain. Where a 12ax7 is rated at 100% gain, and a 5751 is usually rated at 90%, a 12at7 is rated at around 60%. (Again, I'm not really sure where those numbers come from, but I've seen them on charts.)

Neither of those tubes will "neuter" your lead channel. If anything, it makes it sound more brutal because you can hear the notes of the chords more clearly and it sounds tighter when riffing, rather than slightly messy/too much gain. With the 5751 in V1 and a 12at7 in PI on my amp, I normally still don't turn my preamp gain above 5 -- it still has WAY more than enough gain at that level. With my active-pup guitar I set the gain on 4 (using a TS-9 as a boost as well).

I've swapped the two (12at7 in V1, 5751 in PI), and the cleans got even better, but the lead tone got slightly muddy, so I swapped them back. Not a huge difference either way, but I'm an audiophile. If I had to choose only one, I'd probably go with a 12at7 in the PI position, because it really gives you more headroom on your cleans. I also recommend playing with your guitar's volume knob for cleans. Backing it off a bit will help prevent clipping if you accidentally pick too hard. The problem with this amp's cleans is that there's just too much gain everywhere. "Cooler" pickups or rolling back the volume + lower gain tubes can make a huge difference. There's so much F@$#ing gain on the lead channel you won't "run out" no matter what, and most likely, you'll like it better with the added clarity/richness of better tubes.

Originally Posted by the memory

Completed my bi-yearly check that my 6505 still work, still good. Now if my band could hurry up and get some more members I could use it more, maximum bummer!