THAT1512 / Transformer 'blind test' mic preamp

[dmp]

Another thing I don't understand is how the circuit is unbalanced in the SPICE simulation when the pot is set exactly half-way. My understanding was that it's there to adjust for tolerances in the resistors, but in the simulation, the resistors are all exact values.

I feel like I'm missing something really fundamental here.

The top opamp is inverting while the bottom opamp is non-inverting. The gain is different, Rf/Rin vs 1+Rf/Rin

 

[Newmarket]

The top opamp is inverting while the bottom opamp is non-inverting. The gain is different, Rf/Rin vs 1+Rf/Rin

The cross coupling (see R32, R33) takes care of that.

Below is as implemented in DDA AMR24