please check over my FET switching schematic

[darron]

Hi all. Hoping somebody can help me. My theory here is pretty weak. I read over lots of threads and articles, and they all show a similar sort of thing for FET switching.

So I've been working on this circuit for a while. It all works, however, I want to add some new modes to change resistor values for volume levels and frequency cuts. I added 3x JFETS in the schematic below just to add/subtract resistors (R29/R35/R37). WARP-ON and WARP-OFF are just feeding +9V supply from a rotary switch.

I'm hoping it's okay, but it's all too huge to breadboard and test so better ask the experts before going further. So my questions are:

1) Will the FET switching work?

2) I'm concerned for headroom going through the FETs. The first op amp boosts the signal about 5.7x to help combat noise from high resistance LDRs and LFO ticking. So the signal is pretty hot. Especially if you run a booster or something before it. IF I could get all the FET switching to have as much headroom as the op amps then I guess I could get rid of all the relays.

3) What's everyone's favourite FET to use like this? Preferably something I can source easily through Mouser or RS components. My "go-to" stock for all things JFET is SMD 2N5457, however, I bet somebody will tell me it won't be ideal here. If they are okay then awesome.



Please keep the answers semi-simple. THANKS

[PRR]

> Please keep the answers semi-simple. THANKS

That plan is semi-NOT!-simple. Also some misleading: "Vcc" is usually full supply rail but here it is what I would call "Vbias(Vb)".

Q1 Q2 Q3 could be overdriven, but they are followed by Gain stages which will overload before the FET does.

[darron]

Also some misleading: "Vcc" is usually full supply rail but here it is what I would call "Vbias(Vb)".

oops  yeah that's very misleading to read. didn't expect to share this and just threw in a node from the library. take #2! lol