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Old 19th May 2003, 08:58 PM   #11
316a is offline 316a  England
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Default 12AU7

It's a nasty , shrill , 9 pin fart-bottle , a 'trainer' tube . I have seen how these measure compared to a 6SN7/6J5 and the measurements speak for themselves in the sound : a diffused 'tubey' one . Lots of that 'lovely' high order stuff . Use a loctal 7AF7 instead which are electrically identical but actually sound good Otherwise a 6SN7 , 6J5 or 7N7 !

316a
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Old 19th May 2003, 09:30 PM   #12
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Default Re: 12AU7

Quote:
Originally posted by 316a
It's a nasty , shrill , 9 pin fart-bottle , a 'trainer' tube . I have seen how these measure compared to a 6SN7/6J5 and the measurements speak for themselves in the sound : a diffused 'tubey' one . Lots of that 'lovely' high order stuff . Use a loctal 7AF7 instead which are electrically identical but actually sound good Otherwise a 6SN7 , 6J5 or 7N7 !

316a
HOLY CRAP MAN. Lay off the crack pipe sometime!!??!??! Seriously!! Geez.

Here are the curves, height compensated for equal current and voltage scales. 12AU7 curves go in -2Vg steps.

Tim
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Old 19th May 2003, 09:43 PM   #13
dhaen is offline dhaen  Europe
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Default Athiests don't believe in "HOLY CRAP"

The curves look pretty similar don't they...
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Old 19th May 2003, 10:03 PM   #14
316a is offline 316a  England
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Default The curves don't tell the whole story

Crack pipe ? I prefer the ashes and beer-can approach but anyway , don't assume what's in the glass performs exactly to the curves . I wonder just how many new old stock valves test exactly on the money ? Have you tried a 6SN7 etc against a 12AU7 ? If you can honestly say that in the same application a 12AU7 sounds better , I'll eat my whole 12AU7 collection !

316a
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Old 19th May 2003, 10:19 PM   #15
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What is involved in switching my 12au7 preamp over to 6SN7s? ..if the've got the same curves, cant i just throw an Octal socket in there to replace the 9pin and rewire? I've got a foreplay with 2 12AU7s, but my 300b has 6SN7s in it.....might be cool to switch them just for the aesthetics

-Maz
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Old 19th May 2003, 10:23 PM   #16
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Thumbs down BON APPETIT...

Hi,

Quote:
Have you tried a 6SN7 etc against a 12AU7 ? If you can honestly say that in the same application a 12AU7 sounds better , I'll eat my whole 12AU7 collection !
Done that...and there is no comparison.
While the the 6SN7 can really sing the 12AU7A and all its so called equivalents don't even come close.

I usually rely a lot on curves, I even go as far as putting each and every valve I intend to use on the plotter before I decide to use it or not.

The 12AU7A has often given me unexpected results in that it tends to distort like a really bad transistor.
The worst are the French 6189 which sport chromium plated anodes...very odd sounding valve.

Anyway, if you absolutely must use that stash than take Bretts' advise and may the valve gods be with you....
And may I add that I agree 100% with Brett that voltage doublers are a sows' ear sonically.

All SRPP based circuits benefit from a stiff, well regulated B+ supply for the simple reason that the name SRPP: shunt regulated PP is just one hell of a misnomer.

Cheers,
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Old 19th May 2003, 10:28 PM   #17
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Default JUST MOVED...

Hi Maz,

Quote:
What is involved in switching my 12au7 preamp over to 6SN7s? ..if the've got the same curves, cant i just throw an Octal socket in there to replace the 9pin and rewire? I've got a foreplay with 2 12AU7s, but my 300b has 6SN7s in it.....might be cool to switch them just for the aesthetics
Just check heater current and voltage...or consider the 12SN7, much in demand and hence cheaper (and there's a smal raft of others out there) and enjoy a real valve.

Cheers,
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Old 19th May 2003, 10:47 PM   #18
7N7 is offline 7N7  United Kingdom
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Default And me

With my "moniker" you'll guess which side I am on.

And yes I willingly concede that ECC82/12AU7 has a nice set of curves.

Sadly the curves do not, repeat not, tell the whole story.

As EC8010, Fdegrove and 316A have stated it produces a large amount of odd-order distortion; I know I have tested it too.

7N7
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Old 20th May 2003, 12:48 AM   #19
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Default Re: The curves don't tell the whole story

Quote:
Originally posted by 316a
Crack pipe ? I prefer the ashes and beer-can approach but anyway , don't assume what's in the glass performs exactly to the curves . I wonder just how many new old stock valves test exactly on the money ?
The data sheets themselves state that operating points, curves, etc. are based on an average. A typical tube will be maybe 10 or 20% (I don't know the real figure) from that. Note the key word, average, meaning that a random 12AU7 is most likely to fit this curve, though likely with a small bit of deviation; conversely, those which fit tight to the standard as as uncommon as those on the fringes. Also read up on the 'bell curve'.

Quote:
Have you tried a 6SN7 etc against a 12AU7 ? If you can honestly say that in the same application a 12AU7 sounds better , I'll eat my whole 12AU7 collection !

316a
Can't say I've done that yet, but come to think of it I bet I could try it with Hept'AU7.. yeah, wire up an octal socket and hang a 12AU7 on wires. Think I'll go do that, in fact!
I'd try 6SN7 in my preamp but the reason I have 12AU7 in it in the first place is because it only has 600mA of heater available (the other half being used by the AU/AT/AX amp tube).

Tim
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Old 20th May 2003, 01:02 AM   #20
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Default TSSSSKKKK...

Hi Timmy.

Quote:
yeah, wire up an octal socket and hang a 12AU7 on wires. Think I'll go do that, in fact!
Is this how one tests?

Come'on, you know that set-up is worthless, don't you?

Cheers,
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