trinityamps.com

I have read the comments concerning both the 5751 and the 12au7 as possible replacements for lowering the gain. I'm curious what the differences are between the two? and who is using them and what they think?

Thanks in advance

There is a huge difference between the 5751 and 12AU7...

The 5751 has an amplification factor of 70 while the 12AU7 is around 17-19. Compare that to your standard 12AX7 which has an amplification factor of 100...

A 12AU7 will work but it will give you a weak sound. Try the 5751 and maybe a 12AT7 (both of which you can get NOS for cheap these days it seems).

Some good experiences and comments here. viewtopic.php?t=1350

A 5751 is a good option :

Check out Gain Factor

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

There's another point which we mustn't miss - which is that both 12AU7s and 12AT7s are high-current tubes, and bias much hotter than 12AX7s and 5751s. In fact 12AU7s are used as power tubes in some low power amps, such as the Firefly and the Moonlight. So you can get some unexpected or undesirable effects if you try to use them as plug-in replacements for AX7s, since they can end up being biased into a more nonlinear region and can also pull down the preamp rail voltage some. Then it's a crap shoot as to whether an amp really sounds better or not. 5751s bias much closer to 12AX7s, while giving lower gain.

_________________
Great tones come in small glass jars!