Guitar Effects & JFET Splitter

Posted on Feb 6, 2014

This is the schematic of a simple jfet buffer from the Basic Buffers article in the AMZ Lab Notebook, with the addition of pulldown resistors at the input and output. The circuit has a high input impedance and a low output impedance suitable for driving long cable runs or low impedance pedal inputs. Current draw is low and it is quiet and simple t

Guitar Effects & JFET Splitter
Click here to download the full size of the above Circuit.

o construct. A stripboard (veroboard) layout and a pcb design are included in the original article about this circuit. I was looking at the article for the buffer and realized how easy it would be to extend the circuit so that it is a signal splitter. a high impedance input buffer but with multiple independent outputs. All that is required is to parallel extra source follower units with the original. As you can see here, two more fets have been added to the original circuit. Each has separate low impedance drives from their source connections. Since the gate junction of a jfet is extremely high impedance, it does not change the input characteristics of the buffer circuit when additional transistors are put in parallel. With three totally independent buffered outputs, one can be dedicated to a tuner while the remaining two may be used to drive stereo pedal inputs or even two separate amplifiers. This splitter would work great at the input of your pedal chain, immediately after the guitar so that the pickups are loaded by the high impedance of the buffer/splitter. If you want to change the input impedance, the values of R2 and R3 can be altered to suit your taste. If the signal seems too crisp and bright, lower the values of those two resistors to 470k each. Always keep R2 equal to R3. It is not necessary to use all three outputs. If you have a need for only two, leaving the output jack of the third buffer without a plug in...

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