2. tech-talk
  3. 1232169994

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
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
6,032 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).
theclipper
26 posts
 
Bicycle Man,

Thanks for your insight. I know exactly what you mean about the highs. They have a definite edge to them in my setup right now. The bass has been fine for me, I think mostly in part due to my Forte II speakers.

What positions do you have the BB in? Also, I forget, did you end up trying any 5751s?

Thanks,
-Clipper
nsgarch's avatar
nsgarch
2,524 posts
 
Rodman, I danced around with various 6201's after trying some 'normal' TFK and RCA 12AT7's (which weren't bad actually) and also a quad of Mullard CV4024's (which for some reason I didn't really like; which surprised me after all the good things I'd heard), anyway, I liked the Sylvania 6201's a lot (the 2-mica BP gold pins) but the ones I like best (they're not 6201's) are the GEC A2900 (or CV6091 military designation.) These are amazing tubes; really powerful, but smooth as silk, like Gold Lion KT-88's! I was going to try and put together a spare quad but I think the word has got out (damn!) I got my first pair for $85 six months ago, and now they're over $200!! Check the mutual conductance values on these babies, and you'll see what I mean by 'powerful'! http://cgi.ebay.com/2XNOS-A2900-CV6091-12AT7-ECC81-GEC-Great-Britain_W0QQitemZ140298633321QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item140298633321&_trksid=p3286.c0.m14&_trkparms=72%3A1234%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50
.
rodman99999
6,032 posts
 
Sounds like me. I should have stocked up on TungSol 6SN7GT/VT-231 Round Plates($50.00 ea, when I fell in love with them) while I had the chance. I was going to use three 6201's as phase splitter/drivers, but gave up on that amp after getting burned by the transformer builder(paid for, never received). Nothing I own now uses 6201's, so- I've never even heard these.
More to discover