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Old 1st January 2007, 06:53 PM   #1
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Default Low gain 9-pin tubes for Aikido?

Hi,
Are there any choices for low gain 9-pin tubes out there? I'd like to have gain of less then 10. Most tubes like 12AU7 and the likes have gain around 20. It’s too much for the line stage. This will be the Aikido schematic/PCB based project.
Any suggestions?

Thanks
Sergey
Dayton OH
USA
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Old 1st January 2007, 08:03 PM   #2
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The 12B4A is an obvious choice, with a mu of about 6.5. There is also the 7233, with a mu of 4. If you open your scope to 7 pin tubes, there are a few more choices, especially if you consider triode-strapped beam pentodes.
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Old 1st January 2007, 09:02 PM   #3
phn is offline phn  Sweden
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You have seen this?

http://www.tubecad.com/2006/05/blog0064.htm
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Old 1st January 2007, 09:26 PM   #4
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I've seen tha octal Aikido stuff, but the guy was asking about 9-pin tubes, after all. I'm not too interested in the Aikido myself, as a follower is just right, given the overall gain of my system.
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Old 1st January 2007, 09:52 PM   #5
phn is offline phn  Sweden
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Quote:
Originally posted by wrenchone
I've seen tha octal Aikido stuff, but the guy was asking about 9-pin tubes, after all. I'm not too interested in the Aikido myself, as a follower is just right, given the overall gain of my system.
What's your problem?

There are octals AND novals on the page.

And why do you assume I was addressing you and not the thread starter?
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Old 1st January 2007, 09:53 PM   #6
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Quote:
Originally posted by wrenchone
I've seen tha octal Aikido stuff, but the guy was asking about 9-pin tubes, after all. I'm not too interested in the Aikido myself, as a follower is just right, given the overall gain of my system.
Interesting...
I have plenty of gain in my system too. Thats why I've been looking for a very low gain line stage. So, you are sayting that just follower would work well. I'm concern about preservng dynamic qualities of the stage. Is follower just as dynamic as stage with gain? Do you use current source to bias follower tube?
Let me know.

Thanks
Sergey
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Old 2nd January 2007, 12:22 AM   #7
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Gurevise -
I'm using sand state right now for my preamp and RIAA stages (open loop JFET). I've tried a couple of gain-type stages for my line amp, and even at a gain of 5, the volume controls were just too touchy - hence the follower.
I'm in the process of building a vacuum tube preamp using a 6AM4 and 5965 for the RIAA section, and a 6CY7 for the follower line amp. The follower will use solid state current source loading. When I get that built up, I can pass judgement. Unfortunately, that won't happen too soon, as I have at least two projects stacked ahead of it. There's another thread lurking about that I think involves using a 12B4A as a follower - you might want to check that out, as people have actually built the thing and listened to it. I don't know the precise location of the thread, but it should be easy enough to sniff out using the search feature. Good luck whichever way you go.
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Old 2nd January 2007, 04:49 AM   #8
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by gurevise
I have plenty of gain in my system too. Thats why I've been looking for a very low gain line stage. So, you are sayting that just follower would work well. I'm concern about preservng dynamic qualities of the stage. Is follower just as dynamic as stage with gain? Do you use current source to bias follower tube?
Let me know.

Thanks
Sergey
If you want no gain but need a buffer for your volume control, why not try an Aikido follower?: http://www.tubecad.com/2006/06/blog0071.htm

If you just want a little gain, you could also use the 6B4 as suggested earlier. If you look at the Aikido Variations blog early in the sequence, you can use a single triode for the input stage. If did something much like this tacked on to a phono stage and it sounds very nice.

Sheldon
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Old 2nd January 2007, 11:51 PM   #9
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Sergey,

The 12AU7 should give a gain of 8.5. If I read the tubecad site correctly, the gain is 1/2 the mu of the first tube. 12AU7 has a mu of 17, so gain should be 8.5. This is about the value you are looking for.

More details can be found at this link:
http://www.tubecad.com/2004/blog0011.htm

Regards,
Quinnling
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