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Came across these 12AU7s recently and thought I give them a try in my Ayon Spirit amp. Well I'm glad I did. They are the best sounding among my batch of 12AU7s,
PSVANE, RADIOTECHNIQUE, , Cifte, Mullard Vintage NOS and Gold Lion.
They seem to be more dynamic with bit more detail. They are also dead quiet.
Follow Ups:
As VA says, "An individual's gear and taste will cause tubes to be valued differently, sometimes very differently."With tests and lists like this there are typically too many undisclosed variables to make them particularly useful to others. It goes way beyond the the question of, "What gear was used to evaluate the sound qualities of the tubes?"
You also need to ask what role the tube is playing in the circuit. As a preamp? Driver? Phase Inverter? And then, more specifically, "What operating points does the gear use for these tubes?"
So, how are 12AU7s used in the Ayon Spirit amp? As preamps? Drivers? Phase Inverters? At what operating points?
And, while the curves of the 6CG7 are obviously more linear than the 12AU7, that's only meaningful in a DIY context in which you can choose your own operating point.
I assume that TGT doesn't plan on modifying his amp.
I have a lot of vintage gear and not much uses 12AU7s. On a couple of occasions I've looked at their existing operating points and compared them to the 6CG7 at the same operating points. When comparing them on the two graphs, neither one is particularly linear.
It seems that commercial gear tends to run them at much different operating points than a well versed DIYer would.
As a result, I've never seen much point in rewiring the sockets and changing tubes. Especially since the 6CG7 draws twice as much heater current. While that might not be a big deal if you only have a single 12AU7, it adds up fast if you have several.
And, yes, the 6CG7 only runs on 6.3v but, in my experience, it's rare to see the 12A*7 family run at 12.6v, they almost always wired for 6.3v use.
I actually used some 6CG7s for the first time in a Magnavox PP 6V6 console amp that I modded to use directly heated Russian 4P1Ls as outputs.
Edits: 03/31/21 03/31/21 03/31/21
I believe this table is from Steve Hoffman Forums.
I generally agree with the gist of the table IME.
That is from Tube World's owner, Brendan.
A start.
Tre is adamant about the 12au7 being 'distorted' in his word. Apparently it does not have the wide linear swings on a tube curve and harder to implement. I would prefer if he used 'non-linear' because I'm a Marshall amp 'distortion' guy and that's just me. There is one brand not on the list, Tungsram, and it's very nice also, but this list is vague and difficult to aurally distinguish. Words are not enough and people may end up buying all of them.
I have several preamps one of which is a Transcendent preamp, all tubes are 12au7, and although it can drive load with long lengths of cable there is little difference aurally between all the tubes in this list so the circuit used is important.
Ptolomy Almagest
I cannot speak for the 12au7, but I got some GE Military 12at7(6201) a couple of years ago that I am really liking. They seem very forward in the vocals, very detailed, clean, and dead quiet as well. A pair of them is in my Ampex stereo pre. Got a "sleeve" of 5 for 14.99. Glad I did!
You got a real deal, maybe a steal!
You will not thank me for this, and there are good reasons to look no further,
but you have only scratched the surface of the Quest for the Greatest 12AU7.You may have accidentally hit upon the tube that works best for your taste, your music, and your gear.
If so your search is over and thank your stars. However, you might be able to find a tube that works even better for you,
a tube which is worth the effort and $. The key thing is knowing when to acknowledge that what you are
hearing now is certainly fine enough, and may not warrant further fiddling about.Having said that, I never got to the point where I could resist that next audition. So I tried many tubes.
Many tubes. Finally, I did come upon one 12AU7 type which made me think 'this is excellent, this is enough'.
It was a relief to hit that point.
If you are not there yet, let me know and I can provide some candidates to consider.
Edits: 03/27/21
Yes, I would like to know what other tubes I should consider.
Remember, you may not thank me for this.
If you have not already done, it would be useful to use the search function on this forum and
read some of the hundreds of relevant posts-or however many you can read before you burn out.Here are some things I think might help. I have come to believe:
Hypothetically, one could make a list, a rating hierarchy of 12AU7 tubes that will perform well in audio applications.
We don't know precisely what the content of that list is, and we will only ever have a general idea.
An individual's gear and taste will cause tubes to be valued differently, sometimes very differently.
There will not be much difference between tubes that are closely situated on that hierarchy.
Some of the tubes are extinct, or can be considered so for practical reasons.
* One needs to know when to stop looking.I spent lots of $ and time sifting through seven or eight decades worth of 12AU7 tubes.
It has been a very long time since I have closed the lid on those boxes.
Let me pull my buried treasure out the basement and I'll see what I have.
I will take some pictures and describe. Be patient.In the meantime, enjoy your music, and your new GE tubes.
Edits: 03/27/21 03/27/21
For future reference, I doubt the military designation has anything to do with the sound and regular production tubes of this type from the same production period should sound the same. VA is right if you like the tube time to enjoy the music. There are some very good US made 12AU7s and variants but I still prefer the Euro tubes and have never experimented with 7316s.
The 6cg7 will serve the same purpose and is much more linear and therefore should sound better.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
the 6cg7 is said to be the equivalent of a mini-6SN7
The 6cg7 can be used in place of a 12au7. The MU is the same. The trasnconductance is the same. The plate resistance is the same.The pinout is different and the 6cg7 can only be run on 6.3 volts for the heater but both tubes have operating points that are very similar except the 6cg7 is a lot more linear. In a lot of circuits you could just drop the 6cg7 in as long as the heater supply can handle it.
Look at the 6cg7 running at 200vdc plate at 14ma. Now imagine a horizontal load line like you would get with a CCS plate load. That's about as linear as a tube gets. You could use a wide range of load line angles and this would stay linear as there is a large area where the grid line spacing stays symmetrical.
Now look at the 12au7. There isn't anywhere that you can run it and have it be even close to that linear. If the plate voltage doesn't move the same amount (following the load line) for a given increase in grid voltage vs. the same amount of decrease in grid voltage, that will cause an asymmetrical output wave form and that is the definition of harmonic distortion.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 03/28/21
Wait...
" ...The pinout is different and the 6cg7 can only be run on 6.3 volts for the heater... "
that does not sound like a simple drop in.
Correct. I was speaking from a "building from scratch" perspective.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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