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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
rodman99999
6,206 posts
 
Then you disagree, not with me, but the specifications of the tube itself: (http://www.boiaudioworks.com/5751) (http://www.tubedepot.com/5751.html) paragraph 5 of this page:(http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf) (http://www.guitaramplifierblueprinting.com/Tube/5751.pdf) (http://www.guitaramplifierblueprinting.com/files/GE-12AX7.pdf) compare the plate dissipation/transconductance/plate resistance of the 12AX7 and 5751. They are different because the 5751 in not a 12AX7, and has less gain as a result of it's design.
theclipper
27 posts
 
I appreciate the input guys.

So it sounds like the 5751s wouldn't really be necessary for me then? I am just trying to figure out what tubes I should try in my Fisher. I am really curious to experiment and see if I can get a better sound than the JJs are making right now.

Thanks
-Clipper
bicycle_man OP
100 posts
 
I am using a Fisher 400 pre-amp now with Bugle Boy 12ax7's now and am very, very happy with them. This is the pre-amp I was using when I exchanged the JJ's for the BB's recently. With the JJ's I honestly thought I needed a sub-woofer, and when I changed to BB's I realized I didn't. The sound stayed crystal clear, the highs lost the edginess that I heard with the JJ's, the mid-range blossomed into sweetness, and the bass filled out the missing void.

I would recommend Bugle Boy's. The Orange Globe labeled Amperex tubes sound tempting to me. Telefunken's are definitely a step up from JJ's, but I prefer the BB's. The Tele's are very good at everything but miss the magic of the BB's.

For less money, I bet almost all NOS 12ax7's will beat out current production jobs. I have been satisfied with RCA and Sylvania NOS 12ax7's over the JJ's.

Give the tubes time to break-in before jumping to a conclusion. The JJ's became sweeter over time, but in my opinion could not stand up to the NOS tubes that I have.

Happy listening after your search!
nsgarch's avatar
nsgarch
2,524 posts
 
Rodman, when did I ever say they were the same tube? Anyway, if you're talking about the (little used) "amplification factor" curve, yes there is a slight difference, but if you look at the transconductance curves (Gm), the standard measure of gain, the two are almost identical, in fact the 5751 shown in the curves I saw was actually a little higher. Anyway, no (tube) circuit designer in his/her right mind would drive a given tube into that portion of its operating range in the first place.

Having said that, it's well-known that ARC drives their (power) tubes quite hard while McIntosh is quite easy on tubes; which is why you've yet to see a Mac tube amp with mechanical ventilation ;-)
rodman99999
6,206 posts
 
Mr N- Since you mentioned 6201's: I bought four for an amp I was building a few years back, but never used them. I sent two to an AudiogoNer to try, and he bought them. I've still got the other pair, if anyone wants to try them out(free-no strings). Gold pins, triple mica, but I don't know who actually made them(They're labeled Tele ECC801S, but they're not- no diamond).
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