"Passive/Active XLR/SE" i/v board suitable with D60 trafos (for 1:16 and higher turns ratio SUTs) includes AN Silver Niobium i/v resistor across the primary coil and SOTA current buffer on a matched 2sk170/2sj74 jfet pairs. Passive (high impedanced) output and active output (impedance is 25-30R*) are configurable by jumpers on PCB.
SOTA (like UcPure) PSUs of +/-15V are required for active mode