To address this, There is the option of a simple P channel Jfet follower on the input which
raises the input impedance to 100,000 ohms and about 10 pF. Anything will drive this without
problems. The distortion of the P channel Jfet is incredibly low, and doesn't alter the sound in
any significant way, but it assures no impedance interation and a bandwidth to 500 Khz.
The choice of input impedance is made on the jumper of the XLR female connector
associated with each channel on the back of the amplifier next to the input connector. Just
put the gold jumpers into the pins as shown.
You will not damage the amplifier if you change these settings while the amplifier is running,
but I suggest that it's still a good idea to power the amplifier down.
Speaking of frequency response, here is what the amplifier response looks like with the buffer
or with a 25 ohm source in direct mode:
