6550 Question Again

Dax · Post by **Dax** » Thu May 12, 2005 4:22 pm

What is the bias resistor value for:

6550's: is it 27K?
EL34's: is it 47K?

And, EL34's and 6550's fit in the same socket, correct?

Dax

Flames1950 · Post by **Flames1950** » Thu May 12, 2005 6:51 pm

Marshall schematics show 47K for both -- BUT -- they changed the resistor earlier in the bias circuit to compensate instead (I don't have a schem that clearly shows what that value should be for 6550's.) It seems like you end up using a second resistor in parallel to lower the resistor value in line with the bias pot when going from 6550's to EL34's.