How would I wire in a jfet to cut the clippers in a TS type circuit?

[Earthscum]

Can I just wire the jfet in between the clippers and (output?), let the gate float for "on" and pull it to ground for off? Or do I have to bias it? If I have to bias it, it may be out... this is add-on to a board, so not much room.

And what jfet would you recommend? I have MPF102, 2N5457, J201, and 2SK117GR, in order of lowest to highest Vgs. Or highest to lowest?

[PRR]

Link to "TS"?

[CynicalMan]

At first think that sounds okay. With the gate floating or at Vb, Vgs would be 0 and the fet would conduct. With the gate at ground, Vgs would be -4.5 and the fet wouldn't conduct.  No biasing needed, worth trying.

[Earthscum]

I actually came across this thread. http://www.diystompboxes.com/smfforum/index.php?topic=77316.0;wap2

R.G.:
For selecting different clipping devices, you have two main situations, those being when the clipping devices are in the feedback loop of an opamp and when they are connected to ground (or other fixed voltage) on one side.

In the feedback circuit of an opamp, both ends are connected to the same DC voltage, usually a bias voltage on single-supply circuits, or to 0Vdc (not to ground - that's different) for bipolar power supply devices. In this case, the JFETs are trivially simple. You simply put the JFET in series with the clipping diodes and arrange to drive the gate to the off voltage through a large resistance. Generally you would also use a series reverse biased diode and a slow-down capacitor to make the transition be really click and pop-free. No biasing resistors and capacitors are needed because the circuit naturally sits at those voltages.

In the clipper-to-ground circuit, you would use a large (1M or more) resistor from each side of the JFET to ground and if the driving point in the circuit does not itself already sit at ground, a large capacitor to break the DC path through the JFET and clippers. Then the same advice applies - a diode, resistor, and cap from the gate to the gate-drive logic or switch. Notice that for clippers to ground in circuits which use a single positive voltage for power (like a 9V battery in most effects) that a P-channel JFET lets you drive the JFET gate with a positive voltage to turn it off. If you use an N-channel JFET in this circuit, you will have to drive its gate negative to turn it off, and that will require making a negative voltage to drive it from, which complicates things. Generally you can drive the more-common N-channel devices from half of a 9V battery to ground if the source and drain of the JFET are biased up at half the power supply (+4.5V).

Exactly what I was wondering. No bias needed since both sides are at equal voltages. I used a J201, Drain to output, Source to the clippers, and a diode + 1M to switch (switches ground between the gate pulldown or LED that is lower Vf than the other, so it shunts and takes over). The J201 with the clippers in actually has a good resistance and softens the clipping a bit. Makes the clean/dist blend sound better. Pretty good bonus there, if I do say so! And it works great.