[AllanS]

Some well regarded companies have built a reputation around 12AXX tubes in their preamps.  I also found the following harsh critique of their use by a well regarded manufacturer.

“Common preamps tubes are the 12AU7,12AX7, 12AT7, 12AY7, ECC88 ,6922, 6H30, 6SN7 and some rarer NOS tubes.
The most used are the 12AX7,12AU7, 12AT7 tubes. These are cheap, made in a variety of factories are are just about standard in all the low to medium cost preamps.
They were designed to be used in televisions , or as cheap replacements for the older audio only preamp tubes.
They are an inferior audio tube and have no place in a good audio preamplifier.
…for line-stage use its hard to beat an octal 6SN7 tube transformer coupled to the output.”

What gives?  Is the latter an objective generally held position among tube aficionados that 6SN7 is superior to 12AXX in preamps?  Or is the answer like many things, a matter of opinion and perhaps listening preferences?

I know this question has been touched on before but I’ve not found a satisfactory answer.  And maybe there isn’t an answer.

[Early B.]

I agree. Having owned numerous amps and preamps with the 12AXX "baby tubes," 6SN7 is a step up, but it's still entry-level. However, you gotta start somewhere, and if you're just getting into tube gear, then you'll likely begin (and perhaps end) with the baby tubes. That's OK -- you still benefit from the lush tube sound.   

[Freo-1]

I prefer octal tubes in general to the 9 pin mini tubes.  Some of the more interesting tube preamps use a low mu tube, such as the 6S4, or 6AS4.


I'm not a fan of the 6DJ8 family for audio.  They are frame grid tubes, subject to microphonics. 

[FullRangeMan]

12AX7 are used why it deliver 100 times gain what allow a low cost circuit to the manufacturers what are more important than sound quality.

[Tyson]

Octals are the way to go.

[I.Greyhound Fan]

The best 12Ax7 tubes are the Raytheon or Baldwin (same tubes)12AX7 tubes from the 1950's with the long shiny black plates and the Halo Getter. 

They are dynamic, smooth, musical have a hint of warmth.  The midrange with these tubes are excellent.  I own 2 pair and will never sell them. They took a Bellari VP-129 phono preamp from mediocre sounding to sounding very good and way above its price range.

[Rusty Jefferson]

I  don't think many (any?) companies used 12ax7 in the line stage section but rather the phono section of the preamp because phono requires so much gain. Used to be all preamps had phono stages built in.

The 6sn7/12sn7 are more linear than the Noval tubes mentioned and is why many prefer to use them. This doesn't mean there aren't great sounding preamps using Noval tubes. My preference is for 12au7, 6cg7 (Noval equivalent to 6sn7), and 5687 over 12at7/x7, 6dj8, 6h30, etc in Noval tube line stages.

If you decide to go with an octal preamp, try getting one that allows use of (or was built around) the 12sn7 (Linear Tube Audio and I imagine others make preamps that use either). The 12sn7 is exactly the same as 6sn7 but operates on 12 volts instead of 6 volts. The old stock 12sn7 are significantly less expensive than the old stock 6sn7 tubes. There's no reason to run current production tubes in a good preamp. I've curve traced a lot of current production 6sn7 at a friend's house and none have been nearly as linear as any old production varieties tested.

[AllanS]

Thanks much guys.  You gave me plenty to chew on.
EarlyB, your 6SN7 entry level comment was a bit of a surprise so I poked a bit.  I guess I shouldn’t be surprised by how many ways there are to go about the same thing. But I don’t expect I’ll venture off the entry level beaten path as the 6SN7 seems to be a popular choice and readily available.

Rusty thanks for bringing in 12SN7.  I’m seriously considering leaning into the headphone setup and trimming the budget for a proper pre to run a Schiit Aegir.  The Schiit Freya would be the logical choice but the Mapletree 2CRM caught my attention.  It ships with 12S but accommodates 6S.  Searching Tube Depot, Tube Store, and Upscale Audio I’m not finding much in the way of 12SN7.  Am I missing something?

FRM and Larry, I should have thought about it, but phono never even crossed my mind.

[FullRangeMan]

About 6SN7 etc check carefully this image.

[Rusty Jefferson]

....Searching Tube Depot, Tube Store, and Upscale Audio I’m not finding much in the way of 12SN7.  Am I missing something?...

Most good tube dealers should have some. Here's the partial stock list at VTS, but you really have to call to see what's available. I only buy from them now. You can see the difference in cost between 6sn7 and 12sn7 as you scroll down.

https://vintagetubeservices.com/octal-tubes/

[AllanS]

About 6SN7 etc check carefully this image.

Thank you FRM! If available on the internet would you please let me know where to find this?

[AllanS]

Most good tube dealers should have some. Here's the partial stock list at VTS, but you really have to call to see what's available. I only buy from them now. You can see the difference in cost between 6sn7 and 12sn7 as you scroll down.

https://vintagetubeservices.com/octal-tubes/

Many thanks Rusty!

[FullRangeMan]

Thank you FRM! If available on the internet would you please let me know where to find this?

Years ago I found this image, I no have the source.