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12ay7 if operation point does. 12ay7 is a low microphonic low noise version of the 12ax7! Or 12ax7 yugo , cheep and excellent sounding like the Telefunken but more microphonic and more fun/fat sounding/ full body in some distortion circuits ! Don't burn Telefunken unless it is for audio hi-fi sound or recording hi-fi equipment.
Regards Joćo
... the best in my opinion is the ruthlessly neutral Telefunken. They are stronger than most 12ax7s, quieter, sound like they have a flatter frequency response, and are more "out of the way". They are also, predictably, the most expensive in many cases.
For me, the most enjoyable sounding 12ax7s in phono pres and line stages have been Amperex from the 1950s. Also enjoyable have been Mullards (old). RCA are supposed to be great but I have never found a great pair. Both AMperex and Mullard, however, seem to add some lovely euphonic tubey-ness to the sound, whereas Telefunken are almost robotically neutral.
Cheers,
Hukk
I've been researching and testing new (not necessarily NOS) 12AX7 types for my Aesthetix Calpyso linestage. I can hear different amounts of hiss with my ear up to the speaker's tweeter depending on the 12AX7's I have plugged in. Some produce louder hiss while others I can barely hear at all.
I could be wrong, but I don't think you are guaranteed to get a "low noise" tube just by selecting a particular NOS type. My lowest noise tubes are the ones that I specifically requested to be low noise when I purchased them from sellers who have the ability to test for noise.
My two quietest pair of 12AX7's are:
- JJ Tesla 12AX7 "Black Sable" hand selected "Gold" noise grade then Cryogenically treated. Bought from TheTubeDepot.com
- Mullard 12AX7 CV4004 British NOS, hand selected for low noise. Bought from UpscaleAudio Kevin Deal.
Others that were noticeably less quiet:
TJ Full Music 12AX7 from Parts Connexion.
Sovtek 12AX7LPS from TheTubeStore. One is noisier than the other but neither are as quiet as the JJ Tesla and Mullard above.
Tung-Sol reissue 12AX7 from TheTubeStore.
For my application the slight bit of hiss from any of these tubes is not an important factor as I cannot hear any hiss at all from my listening chair. However, it was interesting (for me anyway!) to note the large differences in the amount of hiss these tubes produced with my ear up to the speakers.
I would imagine that the hiss issue is much more important in a mic preamp or phono stage. I would also guess that your chances of getting a truly "low noise" tube is a crap shoot unless your seller is able to test his batch for the lowest possible noise.
I would also guess that if you bought 1/2 a dozen or so new tubes (maybe Sovtek 12AX7LPS), you're likely to find some that are noticeably quieter than the others. I bought a pair of Sovtek 12AX7LPS, one ended up being very quiet and the other not so quiet. And this is just from putting my ear up the speaker. ;-)
Hi, AudioSoul:
I sometimes use original Telefunken "smooth-plate" 12AX7As in my tube - based mic preamps. The other fairly nice sounding and less noisy tubes might be Mullards, but vintage, new old stock, unless you happen to run across some pulls from say, old Fisher tubed receivers and the like.
The best way to "test" them is not only to run them on a good dynamic tube tester but actually putting them in the circuit in question and listening to them, believe it or not.
Tap on them to see how prone they are to microphonics and find yourself a couple which are quiet and sound decent.
The other thing is to see what tube preamp you are using in the first place. Some of the more modern designs do not operate such tubes at full rated plate voltages. Others do. It can make a difference in sonics in my opinion.
My favorite tube mic preamps are a restored Ampex MX-10 with all new caps and other parts and the one dual channel mic pre I use when recording live classical material. That is my Aphex 1100, but it does not use 12AX7As though they can be deployed. It uses Russian military 6-volt tubes and is notonly nearly dead quiet, but sounds terrific.
Good luck!
Richard Links
Links Sound
Berkeley, CA
Selected Sovtek 12AX7LPS.
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