[R-390] R390 NON A IF deck mods

[Flowertime01 at wmconnect.com]

Dan,

There are a lot of tubes that share base diagrams and that can be 
substituted into either the R390 or R390/A.

A lot just depends on the actual tube. It's noise and cut off point will 
vary. Some times better some time worse.

In some stages, (non AGC) the cut off characteristics of the tube do not 
matter. You can plug a lot of different tubes into these stages.

Nice to see a 6AU6 will help get a zero on the meter. Someday you can do 
some signal to noise with a 6AU6 and a 6BA6 and see if the change is better or 
worse in that test.

Roger AI4NI</HTML>