12ax7 preamp.

[longji98]

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

[kevinkr]

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]

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]

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, 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]

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]

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]

check out the following url

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

[jerluwoo]

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]

Originally posted by kevinkr



Nope, 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]

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...