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-   -   12ax7 preamp. (http://www.diyaudio.com/forums/tubes-valves/129534-12ax7-preamp.html)

longji98 10th September 2008 04:20 PM

12ax7 preamp.
 
Hi, everyone.,
I have 2 pcs of jj 12ax7, and want to DIY a preamp . . can someone recommend me a schematics? many thanks

kevinkr 10th September 2008 05:27 PM

Can you be more specific? Line stage or phono pre-amplifier? The 12AX7A would not be near the top of my list as a choice today for a line stage, although all of my older line stage designs used them and sounded quite good.

domjun 10th September 2008 06:00 PM

I just wonder what exactly in the top of your list for line stage preamp.
Is it one of these tubes: 6N30P or 6NP or 12BH7A?

Thanks for your opinion.

kevinkr 10th September 2008 06:24 PM

Quote:

Originally posted by domjun
I just wonder what exactly in the top of your list for line stage preamp.
Is it one of these tubes: 6N30P or 6NP or 12BH7A?

Thanks for your opinion.


Nope, :D My current faves are all dhts 01, 12, and 26 not necessarily in that order. I would also include the 6SN7 and 6J5 in my "second tier." And I use transformers...

mashaffer 10th September 2008 06:36 PM

I don't usually look for opportunities to use GNF but this might be an instance where it would be appropriate. If we are talking line preamp why not a standard CC stage direct coupled to CF with global negative feedback from the output of the CF back to the CC stage to control the excessive gain of the 12AX7.

longji98 10th September 2008 07:29 PM

great Thanks for your reply Kevinkr, I need it just for my bookshelf speaker I made in 6.5". I only have CD player... what do you suggest? thanks again

MQracing 10th September 2008 07:39 PM

check out the following url

http://www.shine7.com/audio/12ax7_pre.htm

jerluwoo 10th September 2008 08:35 PM

2 Attachment(s)
Mashaffer's suggestion is a good place to start. The problem with the 12ax7 is lack of drive current. Don't expect it to drive anything below 40k input impendence very well. Attached is a good starting schematic thats pretty simple to build.

domjun 10th September 2008 09:25 PM

Quote:

Originally posted by kevinkr



Nope, :D My current faves are all dhts 01, 12, and 26 not necessarily in that order. I would also include the 6SN7 and 6J5 in my "second tier." And I use transformers...


Of course you're right.
I have received a pair of 26 from Netherland. Hope I could make them sings in the near time :)

But the first try would be without transformers :(

longji98 11th September 2008 12:15 AM

many thanks to everyone above. ... . another thing is a PT. , what is the minimum specs (requirements) for this 12ax7 preamp. .. voltage and DC current. . .... thanks again...


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