12AU7 vs 6SN7...just snobbery?
Picking up a somewhat old thread here - and quoting Merlin; "Tube-o-philes love to bash the 12AU7, yet with the other hand they are quite happy to recommend the 12AT7, with its equally poor linearity but MUCH worse grid current. The 12AU7 ain't that different from the venerated 6SN7 (lower capacitance though!). From what I can tell the anti-12AU7 thing is 90% snobbery. I love 'em."
Merlin, Well, frankly I'd not use a 12AT7 or any other B9a dual triode valve as my first choice for a high end audio preamp choice.
Seriously, not trying to start a valve war here - but I think there's a bit more to the 12AU7 vs. 6SN7 issue than snobbery.
1.) Whilst the specifications for the xN7 may in some respects appear similar to the 12AU7, there are subtle but important differences. The distortion performance of the 12AU7 is demonstrably and measurably inferior to the entire family of xN7 valves. I mean inferior in ways which are both audible and displeasing to the human ear.
2.) In the purely historic sense, the xN7 dual triodes were designed and engineered specifically to be very low distortion valves. That's because the primary market for the xN7 valve was originally the low distortion/low feedback broadband voltage amplification typical of the 1930's. The 12AU7 simply was not built for that. In fact, it wasn't even primarily designed to be an audio valve. It, along with much of the B9a line, came about in the late 1940's and early 50's. The 12AU7 was designed for the then-new television industry in general, and for driving vertical deflection circuitry in particular, where distortion was of little concern.
3.) Therefore, listening opinions aside, the measurable and "known to be generally audible artifacts" in the form of greater amounts of measurable harmonic distortion in the 12AU7 make it uniformly and significantly inferior to the xN7 valve.
Morgan Jones' trustworthy and thoughtful analysis of a large quantity of valves shows exactly this. ("Valve Amplifiers" Morgan Jones Newnes Publishing) Deliberately setting aside his valve preferences which could colour his investigation, Jones set out to research the issue. He carefully gathered and examined a large sample size of related triode families and brands, including the xN7 families, the Loctal dual triodes, single triode variants as the 6J5, and numerous B9a base valves, in both modern and vintage varieties. Using reliable industry standard methodologies on well calibrated test equipment, it became unarguably evident from the data that the 12AU7 was inferior to the xN7 family. Yes, Jones has published the research, carefully documenting what he found. The numbers are both stunning and definitive to anyone who examines the data. (Unless of course, Jones is lying or incompetent.)
Lest you think Jones was merely descending into snobbery, note that he instituted this rather expensive and laborious process precisely to discover the best valve for a low distortion, low noise, high quality preamp design. During his research he discovered that a lowly and very un-snobbish Russian made single triode (who's maker shall remain unnamed) actually made the best performing triode in the xN7 family. So, rather than talking himself out of what the data had shown by scheduling additional rounds of "listening tests with wine and cheese", he responded to his research data by actually building the design subsequently featured in the book, (the Crystal Palace) using 6J5's made by this very Russian mfg. That's what I call commitment to the data!
Does this mean you can't make a decent sounding 12AU7 circuit? Of course not. Nevertheless, Jones' research strongly intimates that the xN7 family will always outperform the 12AU7 (and most other 9 pin dual triodes) when they are compared using two equally well designed circuits both optimized for their respective valve.
Therefore, one can say with a fair degree of certainty that, if beginning with a blank slate, one is always better to begin with the xN7 family of valves. That's more than snobbery.
Picking up a somewhat old thread here - and quoting Merlin; "Tube-o-philes love to bash the 12AU7, yet with the other hand they are quite happy to recommend the 12AT7, with its equally poor linearity but MUCH worse grid current. The 12AU7 ain't that different from the venerated 6SN7 (lower capacitance though!). From what I can tell the anti-12AU7 thing is 90% snobbery. I love 'em."
Merlin, Well, frankly I'd not use a 12AT7 or any other B9a dual triode valve as my first choice for a high end audio preamp choice.
Seriously, not trying to start a valve war here - but I think there's a bit more to the 12AU7 vs. 6SN7 issue than snobbery.
1.) Whilst the specifications for the xN7 may in some respects appear similar to the 12AU7, there are subtle but important differences. The distortion performance of the 12AU7 is demonstrably and measurably inferior to the entire family of xN7 valves. I mean inferior in ways which are both audible and displeasing to the human ear.
2.) In the purely historic sense, the xN7 dual triodes were designed and engineered specifically to be very low distortion valves. That's because the primary market for the xN7 valve was originally the low distortion/low feedback broadband voltage amplification typical of the 1930's. The 12AU7 simply was not built for that. In fact, it wasn't even primarily designed to be an audio valve. It, along with much of the B9a line, came about in the late 1940's and early 50's. The 12AU7 was designed for the then-new television industry in general, and for driving vertical deflection circuitry in particular, where distortion was of little concern.
3.) Therefore, listening opinions aside, the measurable and "known to be generally audible artifacts" in the form of greater amounts of measurable harmonic distortion in the 12AU7 make it uniformly and significantly inferior to the xN7 valve.
Morgan Jones' trustworthy and thoughtful analysis of a large quantity of valves shows exactly this. ("Valve Amplifiers" Morgan Jones Newnes Publishing) Deliberately setting aside his valve preferences which could colour his investigation, Jones set out to research the issue. He carefully gathered and examined a large sample size of related triode families and brands, including the xN7 families, the Loctal dual triodes, single triode variants as the 6J5, and numerous B9a base valves, in both modern and vintage varieties. Using reliable industry standard methodologies on well calibrated test equipment, it became unarguably evident from the data that the 12AU7 was inferior to the xN7 family. Yes, Jones has published the research, carefully documenting what he found. The numbers are both stunning and definitive to anyone who examines the data. (Unless of course, Jones is lying or incompetent.)
Lest you think Jones was merely descending into snobbery, note that he instituted this rather expensive and laborious process precisely to discover the best valve for a low distortion, low noise, high quality preamp design. During his research he discovered that a lowly and very un-snobbish Russian made single triode (who's maker shall remain unnamed) actually made the best performing triode in the xN7 family. So, rather than talking himself out of what the data had shown by scheduling additional rounds of "listening tests with wine and cheese", he responded to his research data by actually building the design subsequently featured in the book, (the Crystal Palace) using 6J5's made by this very Russian mfg. That's what I call commitment to the data!
Does this mean you can't make a decent sounding 12AU7 circuit? Of course not. Nevertheless, Jones' research strongly intimates that the xN7 family will always outperform the 12AU7 (and most other 9 pin dual triodes) when they are compared using two equally well designed circuits both optimized for their respective valve.
Therefore, one can say with a fair degree of certainty that, if beginning with a blank slate, one is always better to begin with the xN7 family of valves. That's more than snobbery.
I'll name it: Reflektor. To be fair, if he'd had more CV1988, he would probably have used those.
I've repeated some of Morgan's measurements using a somewhat different test setup and had no trouble reproducing them.
Will strongly disagree with that conclusion- the 12AU7, surely. Other 9 pin dual triodes? No. A 6SN7 is demonstrably inferior to, say, an ECC88 for a cathode follower. For a properly designed voltage amplifier, ECC83/12AU7 will give more linearity and higher gain. And so on.
I've repeated some of Morgan's measurements using a somewhat different test setup and had no trouble reproducing them.
Will strongly disagree with that conclusion- the 12AU7, surely. Other 9 pin dual triodes? No. A 6SN7 is demonstrably inferior to, say, an ECC88 for a cathode follower. For a properly designed voltage amplifier, ECC83/12AU7 will give more linearity and higher gain. And so on.
re: E88CC, etc. outperforming xN7 family...
Yes, of course, frame grid 9 pins excepted. We would expect frame grids to be superior, for obvious reasons.
I thought we were discussing 12AU7 and related types as compared to octal based types.
re: "Nonlinearity" Sorry to seem so pedantic, but I suppose I need a better explanation of what you refer to as "linearity". Perhaps my own prejudices are skewing my understanding, but I always grasped linearity conceptually...as wire with gain - (i.e. a broad term encompassing all aspects of gain)
Maybe I'm missing something here, but discussing the term linearity without taking the various kinds of undesirable harmonic artifacts into account seems incomplete. In the broad sense, harmonic distortions certainly seem to me to be a type of non-linearity, if one more broadly grasps linearity as a wire with gain.
What am I missing?
Yes, of course, frame grid 9 pins excepted. We would expect frame grids to be superior, for obvious reasons.
I thought we were discussing 12AU7 and related types as compared to octal based types.
re: "Nonlinearity" Sorry to seem so pedantic, but I suppose I need a better explanation of what you refer to as "linearity". Perhaps my own prejudices are skewing my understanding, but I always grasped linearity conceptually...as wire with gain - (i.e. a broad term encompassing all aspects of gain)
Maybe I'm missing something here, but discussing the term linearity without taking the various kinds of undesirable harmonic artifacts into account seems incomplete. In the broad sense, harmonic distortions certainly seem to me to be a type of non-linearity, if one more broadly grasps linearity as a wire with gain.
What am I missing?
re: E88CC, etc. outperforming xN7 family...
Yes, of course, frame grid 9 pins excepted. We would expect frame grids to be superior, for obvious reasons.
I thought we were discussing 12AU7 and related types as compared to octal based types.
re: "Nonlinearity" Sorry to seem so pedantic, but I suppose I need a better explanation of what you refer to as "linearity". Perhaps my own prejudices are skewing my understanding, but I always grasped linearity conceptually...as wire with gain - (i.e. a broad term encompassing all aspects of gain)
Maybe I'm missing something here, but discussing the term linearity without taking the various kinds of undesirable harmonic artifacts into account seems incomplete. In the broad sense, harmonic distortions certainly seem to me to be a type of non-linearity, if one more broadly grasps linearity as a wire with gain.
What am I missing?
If thread is about the output tubes in an Aikido Phono PCB the discussion of 9 pin vs 6SN7 8 pin is academic. The discussion of linearity is getting the tire wrapped around the axel too.
If you want 6SN7’s use 6CG7’s.
There was speak of Morgan Jones, if you stay away from cutoff and clipping Mr. Jones reports that distortion is proportional to the voltage swing. Considering that the voltage out of the Aikido Phono is less than one volt peak to peak. At the Aikido output the question of how much distortion is there is counted in the number of zeros that follow the decimal point.
For Cosine output, nonlinear means that the half of the curve above the zero line is not symmetrical with the bottom half. At less than 1 volt out the distortion will be difficult to measure.
Try 9AU7's they sound good and the quality ones are cheep.
DT
All just for fun!
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