LJ FET MC Head Amplifier 2020

The present MC Head Amplifier is VERY simple, maybe with the exception of choice of components! 2 paralleled FET (depletion mode) transistors as input gain stage, and one bipolar transistor, emitter follower, as output buffer, also providing a high impedance load for the FET's. Single Voltage supply, amplifier inverts absolute phase. 2SK 389 is a low-noise type FET, originally made for differential amplifiers, (and for that reason should be fairly identical), and 2 transistors in parallel reduce noise a bit more. Also OK gain figures for a FET. Another obvious advantage is the depletion mode property, you can use it without an input capacitor, gate is grounded by R2, which also serves as input load for the moving coil pickup. 2SD 786 is also a low-noise, bipolar, with very low bulk-base resistance. All good things in a moving coil head amp. Not much to say about circuitry, standard layout, the output capacitor (C1) should be large, and can also be a high quality type, bypassing with smaller values is fine. Be careful with load impedance, circuit is sensitive to output load. R6 can be 1 M ohm, but input impedance of the following RIAA amp will in most cases decide the load. No gain adjustment, so the following amplifier(s) should have some gain adjustments, to correct pickups with a small L - R channel unbalance, which is very normal.
A battery PSU could be a great option, or some other low noise type with good CMRR. You can go higher than my 24 V DC supply, but as always, check currents and power dissipation in the transistors. R4/R7 serves as local feedback and input bias, here, preferences are output swing (relevant voltage on FET drain) and margin for MC pickup output (Voltage over R4/R7).

LJ MC FET Head Amplifer, open cabinet
LJ MC FET Head Amplifer, open cabinet. Front: Stereo phono, input and output. Rear: BNC single supply connector, Ground. 2 SK 389 mounted on DIP sockets, to facilitate replacement, or substitution to something else!!
Diagram, LJ MC FET Head Amplifer
Diagram, LJ MC FET Head Amplifer.
Distortion measurement diagram
Distortion diagram. Power supply is my battery supply. Input level is around 20 mV. Signal level is 20 dB down, so the distortion level is 20 dB higher than the figures on the Y axis. As seen in the information for the marker position, bottom left on screen, 988.8 Hz: Second order (blue) is -82.22 dB, Third order is -104.63. Second order dist is clearly dominant, fine with me. Actually, distortion might be lower, since the load for my Fireface soundcard is the FET amp input, only 37 ohms. This is a hard load for a line out, and the soundcard could contribute with a small amount of distortion. In other words, distortion figures are not higher! 20 mV output is on the high side for a normal MC pickup. I also tested with 6 mV, same overall picture, distortion was around 10 dB lower. Frequency response is straight to over 20 KHz. All in all quite ok for a very simple amp!