Seeking a Warm 12AX7 Tube for Preamp

If you’re not opposed to NOS, or used that measure well, try the Raytheon 7025.  A low(er) noise 12AX7 that I have found to generally produce a full sound that is on the warm side.  And they can be found for very reasonable prices. 

Find vintage Telefunken.  Pricey but None better I think.

https://www.audiotubes.com/12ax7.htm

@ spacecadet65

@ knotscott

Which JJ 12AX7 did you purchase?   The ECC83-S or the ECC803-S? 

I have use BOTH and found the 83S more balanced (warmer) than the 803S (analytical) on my Zesto Phono-Pre.

I spoke with the designer, George, who compared the 83S to many, many other tubes- including expensive NOS tubes, and sonically the 83S won (with a bonus - they are cheap $33 - Tube Type: 12AX7 Types (thetubestore.com)).  

In the future I may roll tubes, but I will never be without the 83S... not harsh in the slightest.

@spacecadet65 I bought a bunch of 12AX7, 7025, 5751 and 12AT7 NOS and a couple new production variants to replace a stock JJ 12AX7 that I also found “bright and strident” in a Willsenton R800i 845. The R800i uses one 12AX7 as the V1 signal tube in the preamp section so it has a noticeable impact on tone not withstanding a GFB design. 

The clear winners for “warmth,” which I would describe as enhanced bass response and rolled off treble are the RCA and Brimar black plates. The RCA is the much better of the two, the Brimar is smooth and warm to the point of sounding a bit mushy with lack of detail. The RCAs are warm, smooth and retain detail. A real stand out in my rig is the Raytheon black plate, it is warm yet linear with no high roll off, strong bass, clear airy treble and neutral yet present midrange and superb soundstage depth. Can you tell I really like it!? 

Of the remaining lot, in order of neutral, transparent to detail and airy I’d rank as follows:

GE

Mullard

Telefunken

Gold Lion gold pin from Russia

Sylvania 5751 black plate

RFT

Amperex Bugle Boy

My three favorites are the Raytheon black plate, Telefunken smooth plate, probably the most balanced linear and neutral of the bunch without losing any details, and the Amperex BB. The Amperex is in a class of its own for airy details and a much higher soundstage. The Raytheon has depth and detail with punch, the BB has more detail in the higher frequencies and the soundstage appears two or three feet higher. It’s a great jazz or modern well recorded Indie track tube. 
 

The biggest disappointment is the Mullard. Everyone raves about them online, but in my system, it is just average. Balanced, yes, linear, yes, but nothing special. 
 

It’s possible some of the strident edge is coming from too much gain. You might consider rolling in a 5751 or even a 12AT7 depending on speaker sensitivity. Just a thought.

Cheers,

trivema,

I am pretty much in agreement on your assessment of 12AX7 tubes.  I currently run extremely expensive Telefunken ECC803S (the real deal) tubes in my phono stage.  It is a very dynamic and vivid tube, but, it is not for someone looking for a lot of warmth.  I like other Telefunken variants too.  I am also a big fan of the Amperex Bugle Boys; to me, they are warmer sounding than Telefunkens, but, they remain clear and reasonably dynamic.  I too don't particularly like Mullards.  In addition to being a bit "blah" sounding, in some applications they sound a bit "strange" (sort of phasey sounding).  

I don't really do tube rolling myself, but, I heard a few types when first choosing tubes for my phono stage and in other people's system.  I even tried some 5751s which sounded quite good, although I actually need as much gain as I can get so 12AX7s are a better match.  A friend brought around a big selection of the better tubes he had for me to try.  I liked the Telefunken smooth plates, which is why I went all in on getting the ECC803S when I could do it.