Mesa Boogie 400+ 12au7 swap, any danger?

[Bunyo]

I chabged 12ax7 to 12au7 a year ago, and it was real tone improvement. Now I got some problems with the amp, 6 power tubes are out. My tech suggested me that I shoud use 12ax7 in drive section as was originally. He is afraid that my amp with 12au7
may not work properly, because it was created to work with 12ax7 and that it may affect power tubes.
Do you think that 12au7 swap might cause any dagner to the amp???

[810wmb]

i did the swap on new year's eve of this year.

i read through all of the old threads about the swap. i too would like to know if this will harm the amp...it would be the last thing i need!

[anderbass]

I've been running one in my 400+ for several years now and haven't had any problems. Its just a lower gain tube allowing higher input knob settings to compensate. I think you woulda had the same exact issues with a 12AX7 driver.

[rayzak]

I used mine with the tube swap for a couple years with no issues. Personally, I never thought it made all that big of a difference.

[Bunyo]

Anyone else?

[Nightlyraider]

The tubes you switched out are equivalent in function, but have different gain patterns.

If you didn't change the way you were using the amp before and after the tube switch, the other failures are simply coincidence.

[810wmb]

thanks guys - that is what i gathered from the old thread.

i noticed a difference...a little clearer, more of a "sweep" with the controls. as an added plus, the direct out is not as hot, so i'm not fighting the sound guys as much.