5e7 build - where to use carbon comp resistors?

[ginomolinari]

Thank you! I’ll try it.

[ginomolinari]

So I have watched a couple of Uncle Doug's videos and I think I am starting to understand a few, basic, things. I'd love your comments please. Anyway for my 5e7 project I want to use all metal film resistors but I would like to insert a few tested carbon comp where the make the most difference. According to R.G. Keen, cc resistors should be used only as plate resistors pre phase inverter. I think I may have found them on the layout and schematics. Or am I completely wrong?

Here is the Uncle Doug video I was talking about.
https://www.youtube.com/watch?v=TvQWX0M6hJY

Thanks

[martin manning]

According to R.G. Keen, cc resistors should be used only as plate resistors pre phase inverter. I think I may have found them on the layout and schematics. Or am I completely wrong?

RG recommends against using CC resistors on input stages since the signal level there is lowest, making that the worst place to introduce noise. I would not use CC in the circled locations on the far left on the schematic (far right on the layout).

[ginomolinari]

Martin, thank you for your response. I guess I dont know what Im talking about. But arent those two resistors after the first stage of the preamp? According to schematics there should be 140v on those plates.
So your suggestion is to use them only on the second stage and pre phase inverter then.

[martin manning]

See below.

[ginomolinari]

Interesting. Thank you very much for taking the time to point things out for me. Much appreciated.

[martin manning]

Sorry, I had to make a correction to the mark-up above. The stage I had circled on the right was not the phase inverter, but it is inside the negative feedback loop, and so not a good candidate for CC plate load.