“Blatty” type distortion problem

[andresound]

Great! While you're at it, add some screen resistors as well. 1K - 2.2K, at 3-5 Watts.
At least the tubes will thank you.

Done

[Littlewyan]

With regards to the screen grid resistors I couldn't find any info on these in the datasheet. Nor could I find anything on Google regarding it. Maybe they don't need them and the decoupling resistor (or choke resistor) is enough at 1K.

As I understand it, decoupling resistors or chokes don't really function as a screen resistors. That is, basically dropping voltage for the screen along with the plate when the tube is pushed. Some old or small/cheap amps sometimes lack these resistors.
But I guess the "need" for them might depend on the idle difference between plate and screen, and how much the plate actually drops. I've just kind of learned that screen resistors are good practice.

They generally are, ESPECIALLY if you are pushing the output stage into distortion. Looks like Andresound has added them anyway, it wouldn't hurt even if they didn't need them.

[andresound]

I added 1k screen resistors. I will revisit the amp tomorrow, and draw the final circuit.

[andresound]

Herewith is the final amp as built. I had interference from the 1k screen on pentodes, so removed them again. The 52k grid stoppers solved my strange sine wave problem. Started with 10k as suggested, but eventually ended up with 52k.

Please beware... there might be errors in my drawing. Thank you everyone for the help.

[Littlewyan]

Glad to hear it's sorted