First time 12AX7s sound better than 5751s for cleans

[talltxguy]

When it came to 5751s vs 12AX7s, I always thought 5751s sounded better for cleans in nearly every amp I've owned; so naturally I replaced the stock Mesa 12AX7s with NOS 5751s. "Meh" sums it up best. I put some NOS 12AX7s in there and was blown away.

I understand that the Lone Star was designed to run 12AX7s. But so were all of the other amps where 5751s ruled the cleans. I'm just curious why the 12AX7s seem to work better than 5751s in the Lone Star preamp.

Any insights would be appreciated.

 

[djw]

I found a 5751 did some nice things for the DIRT in my amp, actually. Lowered the gain so I could crank the master a bit more and get a fuller tone with slightly less volume.

But I switched back to a 12AX7. I would guess that part of what makes the Lone Star cleans what they are is the warmth, and having adequate gain in those stages are probably a big part of that. Just a guess though, I don't have any technical insight.

 

[Heritage Softail]

I have also used NOS 5751's to tame unruly high gain amps a bit. It seemed it let the gain come on more slowly. The difference was is the lower third of the gain knob to me. For lower gain amps, like the Bogner New Yorker, 1950's type Fender clone, is makes no difference.

But at this time, the only Mesa amps I have are high gain. And they have Chinese square getter type 12ax7 high output tubes to let the beast scream. I can't help it though. Something about the old MKIIC breathing fire just works. :lol: