Gates SA70 with 5840 tubes? Need help with biasing.

[rock soderstrom]

Radiotron Designers Handbook third edition, chapter 34 (pdf page 273).

Thanks for the link

I have read some other sources on the web about this topic, but it seems RDHB is better to understand, at least for me.

 

[emrr]

Adapting a traditional feedback circuit would be a different amp and erase what makes this one unique.

 

[rock soderstrom]

I think you are right.

There is nothing wrong with trying new things by combining existing things. The result will just be something different. For this project, I'll probably stick with the original circuit (as far as it makes sense) since I'm already changing tube types. I'm actually interested in what influence the tubes have on the sound, in (almost) the same environment. Subminiature vs steel octal tubes - fight!

 

[mhelin]

Adapting a traditional feedback circuit would be a different amp and erase what makes this one unique.

Yes and there are already preamps like the NYD one-bottle like that.

 

[rock soderstrom]

Ok, I modified my plans slightly, because the transformer and other components define the overall height of the mic pre and thus the size advantages of the 5840 do not really come into play.

Therefore now the larger version of the 5840, the 5654, 6Ak5w or also called E95F.

Here is a WIP design, almost ready for etching - the MINI SA70

 

[emrr]

Make sure to put radial cap pads on C9/C11 if you think this is gonna stick around.

 

[rock soderstrom]

Make sure to put radial cap pads on C9/C11 if you think this is gonna stick around.

I will do that, other components will also have variable footprints so you can use the components you have available. The current design represents what I have lying around.

 

[rock soderstrom]

First prototype is ready for etching. Two of them fit on one standard eurocard (160x100mm).