Intro and switch transient question

[Rob22315]

Saying hi since this is my first post. I came here looking for tips on how to add a buffer preamp (vol and tone are still passive) to my bass.

Thanks to the great tips here, I was able to adapt the tillman/Hugsley preamp to my bass guitar and it works great. I added a switch so I could switch between passive and active. The 9v battery switch too (DPDT). I get a wicked pop when I switch from passive to active, any way to cure this? Note, I do not have the .1microfarad cap on the input to the JFET as shown in Hugley's layout, only a 3M resister. Would that fix it?

I'm sure the answer is simple but I haven't done electronics in a while and a quick search didn't help.

Thanks in advance.

 

[DF96]

I am not familiar with the circuit, but you must always ensure that when switching signals the DC level is the same. This usually requires a DC blocking capacitor and a resistor to ground for each input, if these are not included in the preceding unit. If you have omitted a capacitor then this could be the cause.

 

[Rob22315]

That would do it. I have one I can add easily enough.

 

[Rob22315]

The circuit I built looks very similar to the one in post 81 at the link below:

http://www.diyaudio.com/forums/musical-instruments/27524-new-jfet-guitar-preamp-project-9.html

My resistor values are tuned to my JFET and I left out the cap on the input.