Hifisonix Discrete JFET Input Line Stage

This discrete JFET input line stage can drive a 2k ohm load to 6V RMS in class A at less than 30 ppm distortion and at 3V RMS into 2k ohms, the distortion is around 7ppm at 1 kHz. The output stage runs at 20mA standing current. A jumper allows the user to select either standard Miller Compensation, or Transitional Miller Compensation (TMC). Output mute relays can be controlled by a user provided circuit, or, they can be driven off the /MUTE output available on the Hifisonix Standard PSU.

Click here for the schematic

Click here for the BOM

Here are some performance measurements using the Texas Instruments JFE2140 dual JFET in place of the LSK389 originally specified. The TI device offers better device matching and slightly lower overall noise – its also readily available from Mouser

Click here to buy a PCB in the shop