Another tube question

TEAforONE

While shopping for tubes,I noticed that 12ax7's command a higher price than 12at7's. Is this simply supply and demand,or is there more to the story?
Thanks in advance,
Ray

marvda1

6dj8's even more expensive.

heiney9

Supply and demand.....mostly demand. 12AX7 were used a lot more. Also in guitar amps as well. Also there is probably more "mystic" (for lack of a better word) attached to the 12AX7 since it was/is more popular.

H9

TEAforONE

heiney9 wrote: »

Supply and demand.....mostly demand. 12AX7 were used a lot more. Also in guitar amps as well. Also there is probably more "mystic" (for lack of a better word) attached to the 12AX7 since it was/is more popular.

H9

Thanks for the answer.

mhardy6647

The 12AX7 has a high enough amplification factor for use as a moving magnet or tape head (pre) amplifier -- it is not so straightforward to do that with a 12AT7 or a 12AU7 (multiple gain stages would be required).

Personally, and strictly FWIW, I am not much of a 12AX7 fan for anything -- much less 6922s -- their Octal cousins get my vote
12AU7 and 12AT7 can make very decent driver stages (voltage amplifiers) in tube amplifiers, FWIW (although I still kinda sorta prefer their octal colleagues).

Speaking of which - and distressingly but not unpredictably off-topic - here're a couple of interesting pieces about the history of the 6SN7 (a personal fave in terms of medium mu twin triodes) -- strictly FWIW, of course.
http://vinylsavor.blogspot.com/2014/02/tube-of-month-6sn7.html
http://www.fourwater.com/files/hist6sn7.txt

The octal "equivalent" (ish) of the 12AX7 or 6922 would be, e.g., the 6SL7 (amplification factor = 70)... the real 12AX7, of course, has an amplification factor or 100.

headrott

12AX7's are a very common tube, yet there are certain brands and the way they are made that make for a high demand and high cost tube as the "good ones" or "best ones" haven't been manufactured for about 40 to 50 (+/-) years now.

You can get current manufactured 12AX7's (typically ade in Russia) for relatively cheap. However, they don't sound nearly as good (especially in the tonality department, and probably the soundstage too) as the older 50's and 60's 12AX7's. There are preferred brands and tube designs even in the 50's and 60's tubes too.

TEAforONE

mhardy6647 wrote: »

The 12AX7 has a high enough amplification factor for use as a moving magnet or tape head (pre) amplifier -- it is not so straightforward to do that with a 12AT7 or a 12AU7 (multiple gain stages would be required).

Personally, and strictly FWIW, I am not much of a 12AX7 fan for anything -- much less 6922s -- their Octal cousins get my vote
12AU7 and 12AT7 can make very decent driver stages (voltage amplifiers) in tube amplifiers, FWIW (although I still kinda sorta prefer their octal colleagues).

Speaking of which - and distressingly but not unpredictably off-topic - here're a couple of interesting pieces about the history of the 6SN7 (a personal fave in terms of medium mu twin triodes) -- strictly FWIW, of course.
http://vinylsavor.blogspot.com/2014/02/tube-of-month-6sn7.html
http://www.fourwater.com/files/hist6sn7.txt

The octal "equivalent" (ish) of the 12AX7 or 6922 would be, e.g., the 6SL7 (amplification factor = 70)... the real 12AX7, of course, has an amplification factor or 100.

Mark,Why don't you care for 12ax7's? Too much gain?

mhardy6647

Just, to me, there are better sounding twin triodes (or single triodes, as the case may be). The 12AX7 or 6922 is OK for phono/mic/tape head preamp use, but (strictly IMO) they're not a great choice for use as drivers or phase splitters.

They were cheap and plentiful in their time, and vintage amplifiers ('specially cheaper ones) tended to be full of 'em. I think my EICO HF-85 (stereo full-function preamp), e.g., has... umm... five of em. Yup, per Sams 482. Ten high mu triode sections in toto in that bad boy.



Make no misake: miniature tubes do have real advantages for high-frequency (e.g., radio and TV) signal applications, but not so much for audio-frequency components.

verb

mhardy6647 wrote: »

The 12AX7 has a high enough amplification factor for use as a moving magnet or tape head (pre) amplifier -- it is not so straightforward to do that with a 12AT7 or a 12AU7 (multiple gain stages would be required).

Personally, and strictly FWIW, I am not much of a 12AX7 fan for anything -- much less 6922s -- their Octal cousins get my vote
12AU7 and 12AT7 can make very decent driver stages (voltage amplifiers) in tube amplifiers, FWIW (although I still kinda sorta prefer their octal colleagues).

Speaking of which - and distressingly but not unpredictably off-topic - here're a couple of interesting pieces about the history of the 6SN7 (a personal fave in terms of medium mu twin triodes) -- strictly FWIW, of course.
http://vinylsavor.blogspot.com/2014/02/tube-of-month-6sn7.html
http://www.fourwater.com/files/hist6sn7.txt

The octal "equivalent" (ish) of the 12AX7 or 6922 would be, e.g., the 6SL7 (amplification factor = 70)... the real 12AX7, of course, has an amplification factor or 100.

Wow Mark, I counted 3 "FWIW" in that post. IMO, very informative and interesting! Thank you, FWIW

treitz3

mhardy6647 wrote: »

Personally, and strictly FWIW, I am not much of a 12AX7 fan for anything -- much less 6922s -- their Octal cousins get my vote

Talk to me about these "octal cousins" if you don't mind. What in the heck do they do differently?

Tom

mhardy6647

Give a listen.
To me, circuits using the octal twin triodes (or single triodes, like the 6J5, or even their 4-pin forebears, like the 76 or 27) (EDIT) generally just... sound better.
More like real music, which is what I look for in this furshlugginer hobby.
YMMV, of course.

Thus all the FWIWs before -- just my opinion(s), you know?

marvda1

here's what deHavilland had to say on a q&a about the 6sn7 tube.

Q: And the 6SN7?

A: The 6SN7 is a tube that SE people describe as having "Big Tone". It is a dual triode that has a very open, relaxed and graceful sound, without sacrificing detail. Introduced by RCA in 1939, it is hard to find a driver tube that is more rugged, and sonically consistent.

verb

mhardy6647 wrote: »

Give a listen.
To me, circuits using the octal twin triodes (or single triodes, like the 6J5, or even their 4-pin forebears, like the 76 or 27) (EDIT) generally just... sound better.
More like real music, which is what I look for in this furshlugginer hobby.
YMMV, of course.

Thus all the FWIWs before -- just my opinion(s), you know?

Interesting Doc. So I did a quick search, and they do make adapters for the 9 pin miniatures to octal. Have you tried that?

mhardy6647

marvda1 wrote: »

here's what deHavilland had to say on a q&a about the 6sn7 tube.

Q: And the 6SN7?

A: The 6SN7 is a tube that SE people describe as having "Big Tone". It is a dual triode that has a very open, relaxed and graceful sound, without sacrificing detail. Introduced by RCA in 1939, it is hard to find a driver tube that is more rugged, and sonically consistent.

That sounds good to me.

pitdogg2

Well are those 12xx7's getting 12 volts the the heater? How do those adaptors nagate that extra 6 volts too much?

Asking for a friend

mhardy6647

verb wrote: »

mhardy6647 wrote: »

Give a listen.
To me, circuits using the octal twin triodes (or single triodes, like the 6J5, or even their 4-pin forebears, like the 76 or 27) (EDIT) generally just... sound better.
More like real music, which is what I look for in this furshlugginer hobby.
YMMV, of course.

Thus all the FWIWs before -- just my opinion(s), you know?

Interesting Doc. So I did a quick search, and they do make adapters for the 9 pin miniatures to octal. Have you tried that?

that's kind of like adapting a 1.5 liter turbo 4 into a car currently sporting a 5 liter V8 (or vice versa). I mean... you can...


Now, there are tubes that are identical except for their envelopes -- the 6AQ5 and the 6V6 power tubes for example; swap the pinouts and sockets and they're essentially interchangeable.

The B9A base twin triodes are all sorta interchangeable with each other*, and they generally have (for lack of a better word) cognates in 8BD base twin triodes, but AFAIK most if not all are apples to apples. In other words, a 12AX7 isn't a 6SL7 in a 9 pin miniature envelope. The 8BD twin triodes are (mostly) sorta kinda interchangeable, too, but that doesn't mean that, e.g., a 6SN7 is going to work
properly in place of a 6SL7 -- even though it'll probably work in some sense of the word.

Also -- don't forget about filament current requirements

EDIT: The 6SN7 did chase into a couple of 9-pin 'cognates':
https://en.wikipedia.org/wiki/6SN7#Successors_to_the_6SN7

6SL7 gets a little more complicated (i.e., I don't know nothin' about this/these)
https://www.diyaudio.com/forums/tubes-valves/329556-6sl7-equivalent.html
https://www.diyaudio.com/forums/tubes-valves/15430-single-section-equivalent-6sl7.html

apparently the 5751 is pretty similar operationally to the 6SL7:
https://www.audioasylum.com/audio/tubes/messages/23/235913.html
______________

* here's my handy little table of B9A tubes that I am typically interested in, e.g.:

mhardy6647

pitdogg2 wrote: »

Well are those 12xx7's getting 12 volts the the heater? How do those adaptors nagate that extra 6 volts too much?

Asking for a friend

Don't forget that the 12V filament in a 12AX7 (B9A-base) tube is center-tapped; the filaments can be operated in series or parallel, which is why (I think) you'll find 'em in components that otherwise are otherwise all 6V tubes (except -- often, of course -- the HV rectifiers, which use 5V filaments).

verb

Doc you are walking tube encyclopedia! Thank you! I’ll stick with the 6SN7 to 7N7 (IIRC) adapter!

TEAforONE

This is way above my pay grade. I'm trying,though!

mhardy6647

Well... I mean, if you have a component that uses 12AX7s... stick with 12AX7s
It's not like there aren't good ones... it's just that you'll pay for 'em.
Personally, I am happy enough with good ol' US made 12AX7s from the 1950s or even '60s. Not top echelon, but you won't have to sell a kidney to buy a quad of 'em, either.

If you can give up a little oompf, though, you can always try 5751s.

TEAforONE

mhardy6647 wrote: »

Well... I mean, if you have a component that uses 12AX7s... stick with 12AX7s
It's not like there aren't good ones... it's just that you'll pay for 'em.
Personally, I am happy enough with good ol' US made 12AX7s from the 1950s or even '60s. Not top echelon, but you won't have to sell a kidney to buy a quad of 'em, either.

If you can give up a little oompf, though, you can always try 5751s.

These tubes are for my Aric Audio preamp. The way Aric designed this,the end user can roll,in 12au7's,12at7's,and 12ax7's. So,I've been playing with rolling signal tubes. That is why I was curious as to the higher prices for 12ax7's. The next tubes coming in are a pair of 1957 RCA black plate 12au7's,and a pair of RCA long gray plate clear top 12au7's.

Also of note,this pre has a gain adjustment on the rear. This comes in very handy when I rotate amps.

Faustin

[/quote]
These tubes are for my Aric Audio preamp. The way Aric designed this,the end user can roll,in 12au7's,12at7's,and 12ax7's. So,I've been playing with rolling signal tubes. That is why I was curious as to the higher prices for 12ax7's. The next tubes coming in are a pair of 1957 RCA black plate 12au7's,and a pair of RCA long gray plate clear top 12au7's.

Also of note,this pre has a gain adjustment on the rear. This comes in very handy when I rotate amps.
[/quote]

I as well have an Aric Audio Transcend preamp with a phono stage. When I purchased it from the previous owner, it came with 12at7's in all positions. I had it coupled to Bottlehead Paramount 300B monoblocks and single driver full range speakers. Since the pre can use several varieties of 12a tubes, I didn't give it much thought. I did roll in some other 12at7 tubes from my stash, but I really was not liking the sound of the setup at all. Didn't know if it was the pre, amps, speakers or?? Used the speakers with a rebuilt Fisher X-100 and that setup sounded great. I was ready to just sell the amps thinking that the 300B sound was not for me. Then for some reason I decided to swap out the 12at7's for some 12ax7's. It was a stunning change. People talk about the drastic changes by rolling different manufacturers tubes, but to be honest with you, most of the time I am not hearing a big difference. This though, was so different. Before the sound was thin and sometimes shrill on the high end. I was blown away by the change.

Before I swapped the tubes, I had been corresponding with Aric about some general info about the pre amp. When I shared my tube swapping experience with him, he indicated that he really designed that pre around the 12ax7 tube. Others flavors will work, but.......

On a side note, the Bottlehead Paramounts use a 5670 (396a) tube. The later version can use a 6sn7 in place of the 5670. Through the BH forum, I found some nice adapters which allowed me to roll in 6sn7 tubes. Richer, open sound.