I made this preamp buffer a couple of months ago but never got around to doing a writeup on this. This has pads for through hole as well as smd also, so most of the jfets can be used like 2sk170, bf862 and others. This build uses 2sk170 at around 8ma. I plan to try bf862 also, but that will take some time as those will be a pain to match. It needs 4 jfets. Input and outputs both are dc coupled, though my amp has a cap at the input.
It has a dual shunt regulated power supply running at around 50ma right now. It can be run at a much higher current also once suitable heatsinks are added, currently it uses very small heatsinks on the ccs transistor, nothing on the shunt transistors. If equal voltage rails are desired, zeners can be matched. I am using 9.1v zeners which give me about 9.65v rails. I am using a 15v transformer. Since its a shunt regulated supply, the voltage requirements are more than the usual LM3x7 regulators, it will easily need some 7-8 volts minimum extra over the output voltage. Small transistors are bc550/bc560.
Some pictures:
bare board -
partially soldered board -
Complete board -
It has a dual shunt regulated power supply running at around 50ma right now. It can be run at a much higher current also once suitable heatsinks are added, currently it uses very small heatsinks on the ccs transistor, nothing on the shunt transistors. If equal voltage rails are desired, zeners can be matched. I am using 9.1v zeners which give me about 9.65v rails. I am using a 15v transformer. Since its a shunt regulated supply, the voltage requirements are more than the usual LM3x7 regulators, it will easily need some 7-8 volts minimum extra over the output voltage. Small transistors are bc550/bc560.
Some pictures:
bare board -
partially soldered board -
Complete board -
