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Rolled some 12ax7's recently...

Hi All,
I went through my supply of 12ax7's recently and found some goodies.
I recently compared Bugle Boys to Telefunkens in the phono stage of my pre-amp. Interesting (to me, at least). I found the Telefunkens to be nice sounding; very clean and clear, very nice detail, over all a very nice sounding tube. The Bugle Boys, however, were magical! WOW! Timbre was so much more apparent. The soundstage depth and width increased; especially the depth. The music seemed to come alive and glow. It was much more captivating.
I found such a dramatic difference between two high quality tubes very interesting.
I have yet to try 10m's, and 70's Mullards that I found. I will report when I do...
By the way, NOS Sylvania's sound nice in the line-level stage. All tubes reported are vintage NOS. I match them with my tube tester. And, I do not change the volume setting between tube brands tested.
Any comments are more than welcomed! I appreciate any information on your experiences with 12ax7's. The price of some of these NOS is incredible; I am glad to have these nice examples in my collection!
Cheers.
bicycle_man
fbi
92 posts
 
~~~~Nsgarch, You are correct. They have deeeep natural bass, wonderful presence, and extended highs. Now if I could get them to wash the car, walk the dog, and cut the grass...Now were talkin!

Just The Facts
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abucktwoeighty's avatar
abucktwoeighty
1,079 posts
 
Fbi, Nsgarch, I have Svetlana 12AX7's in my modded Jolida JD100 CDP, and am now thinking of trying the 5751's. Nsgarch, you mentioned the 5751'a are spec'd at 70%-80% the gain of the 12AX7's. I'm presently using a set of Rothwell 10db attenuators with the Jolida to help with the gain. Sounds like the 5751's will help a little more in that respect.
rlawry
477 posts
 
Best 12AX7 I have tried is the very rare and expensive CBS/Raytheon D-getter 7729. I also have a pair of O-getters that are close, but avoid the later CBS/Raytheon with the O-getter and 7729 etched in the glass. These last ones were actually made by GE and sound rather ordinary. Once I heard these I sold my Telefunken ECC803S, a nice tube but thin and lean tonally in comparison.
thorman
1,262 posts
 
Two best 5751 I have tried is Ge 5751 3 mica Black plate and the RCA 5751 3 mica black plate..The Ge is more neutral,but the RCA has more body and weight..Both Great tubes..Each will work great with proper system synergy....
nsgarch's avatar
nsgarch
2,524 posts
 
Abucktwoeighty -- I can't say for sure about your CDP application, but let's just say don't count on less output because you're running 5751's ;-)

If you compare performance (tube) curves between a 12AX7 and 5751, you'll note that the curves are essentially the same until the upper limit of operation where the 5751 drops of some. HOWEVER, I don't think any circuit designer would use either tube where it would be driven to the limit -- there would be other tubes to choose from.

Also, keep in mind that the 5751 was originally developed as a 'ruggedized' tube for the military - so it would have to perform the same as any 12AX7 it would replace.
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