I'm planning on building a mic with a EF86. I'm just little confused about the transformer choice. Internet seem to suggest about 7:1 ratio (U67,MK7,G7) but when I try to calculate it I end up with much higher ratio. I used U67 parameters for this load line (210 B+, 150k Rp, ~-2V bias) and no matter how I try to tweak the tangent I end up with ~35k plate resistance. With the 150k plate resistor in a U67 this equals about 28k output impedance, which needs about 12:1 ratio for ~200 ohm output.
What am I missing here (something for sure)?
What am I missing here (something for sure)?