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Mullard 12AU7A/ECC82?

DennyOnBass

DennyOnBass

Dec 18, 2003
1,138
1,032
59
Traverse City, MI
#1
I was visiting a friend this weekend and he invited me to rifle through a box of tubes he's had sitting unused in his basement for over 10 years. Most of them were typical tubes/brands that I had no real use for, but among the collection was a Mullard 12AU7A/ECC82 that I ended up taking.

So, I'm thinking about either putting it in my Genz Benz Shuttle 9.0 that I use for live shows or my Alembic F-1X pre that I use for recording sessions. What kind of a difference might I anticipate over a standard 12AX7? Which of the two would you put the tube in?

I'm guessing that the Alembic might benefit more, but I use the Shuttle more often.
 
#2
Depends of the amp and it's board design .

If it was a hand made tube amp like a Reeves , then you could hear
the difference as soon as you played it .

On the other kind of amps , I suspect that you can hear a difference , but how much it will effect your tone is up for grabs until you install the tube and play it .

A Mullard in the V1 position of your preamp should make it sweeter and more musical . Also , a 12au7 will be a lot cleaner than a 12ax7 for example and will boost the input signal some .
 
#3
I think you will find that while the 12AU7 might give you a cleaner signal it will do it by decreasing the signal rather than boosting it, so that you may get an apparent volume loss - although this should be compensated for by being able to turn the volume up further without distortion. I am not a tube expert, but this is based on my tube swapping experiences with my old Mesa 400+. I am sure that the 12AU7 has less "gain" than a 12AX7, although they can be safely substituted for each other.
 
#4
Modulator said:
............. but among the collection was a Mullard 12AU7A/ECC82 that I ended up taking. What kind of a difference might I anticipate over a standard 12AX7? Which of the two would you put the tube in?
Click to expand...

IMO, neither one. while it won't hurt anything to try it, the gain of the 12AU7 is far lower than a 12AX7 and i never substitute one for the other. the AX has a gain factor of 100, whereas the AU has a gain factor of 19. the only tube that i'd recommend to be substituted for an AX is a 5751, and that is to lower the gain of a hot preamp, since it has a gain factor of 70.
 
#6
Yeah, it doesn't sound like anything I would want...I got excited when I saw the name Mullard on it, but a gain reduction isn't going to get me anywhere I want to be.

I'll probably pop it into the Alembic to see what it sounds like, but I'll probably ultimately pass it off to somebody else...
 

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