mu stage help...

[AudioGeek]

I am looking to build a mu stage with gain 20-30 using a mosfet as the upper device.

It will only have to have an output voltage swing of 60vpp.

Thinking ECC99, 6SN7, etc...

what op point should I run them at?

Thanks!

 

[Geek]

http://www.tubecad.com has some good hybrid designs in their back issues.

 

[Sch3mat1c]

ECC88/6DJ8/6922 will do it. Somewhere around 10mA. Minimum supply (to meet the required voltage output) is around 100V, and bias will be 1V (100 ohms Rk) for +100V supply, 3V (270 ohms) for +200V. Etc.

Tim

 

[AudioGeek]

hm.

i like tubes with grid bias >1v though....

plus the 6922 has a sort of bad vibe around it.

unless you know of a good brand?

 

[Sch3mat1c]

Um... suit yourself... but the electrical properties of what I spoke of are perfectly sound. Meta-acoustics don't apply when I post.

Tim