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Old 27th May 2021, 12:22 pm   #20
Jez1234
Pentode
 
Join Date: Mar 2021
Location: Morpeth, Northumberland, UK.
Posts: 111
Default Re: Advice on this linestage build

Quote:
Originally Posted by Robert Gribnau View Post
Hello Jez,

Quote:
Originally Posted by Jez1234 View Post
EF86 or better still EF184 in pentode form giving around x 400 gain followed by a cathode follower then wrap the feedback around the Baxandall network.
Could you give values for Vb, Ra, Rg2 and Rk to achieve a gain of 400 with an EF86 and an EF184?

Quote:
Originally Posted by Jez1234 View Post
FWIW after seeing reports of super linearity from EF86 when triode strapped I tried it....

It's not true! I tried several samples, tried different methods of triode strapping and experimented with load line etc and distortion was disappointing.

Can you share some of your test results with us? Did your results differ from the distortion figures in this datasheet (see page 3), and if so, in what way? https://frank.pocnet.net/sheets/030/e/EF86.pdf
I'm afraid I have better things to do than act as a free R & D service! There will be many designs already around. With active load you can get gains of thousands!

The distortion figures in that datasheet look about right yes and similar to what I obtained. There is a Svetlana datasheet suggesting 0.1% for something like 10V output!! No way. Suggestions of triode strapped EF86 being super linear abound on the internet also....
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