Buffer click problem

[gtudoran]

Hello guys, i run into  a little problem.
A guy asked me to build a buffer that he will put into a guitar, so it will be always on when the cable is pluged in. So i've made the AMZ Jfet Buffer for Guitar from this link http://www.muzique.com/schem/eagle.htm.
But there is a problem... when guitar is inserted in any FX pedal (i've tryed with all kind of pedals) there is a pop at switching when the pedal in in FX mode.
I've tryed a smaller output cap like 0.1uF i've tryed smaller output rezistor (i went from 100k to 10k) there was no improvement.
I got a 9v battery as a power supply ... no substitutions ware made ...but i'm out of ideas..

Best regards,
Gabriel Tudoran
Analog Sound

[WangoFett]

Hey.
Check the DC level on the output of the buffer you built.  Perhaps the output coupling capacitor (C2) is leaky.  This would cause popping down stream in true-bypass pedals when they are stomped.
Also, if you are using a polarized cap for C2 (e.g. tant or electrolytic), check that it is installed the right way around.

[gtudoran]

I used a 1uF cap first and the + pin was to the source of the jfet and the negative pin to output, then i tryed with 0.1u and 2.2n same pop... if some voltage is present at the output what could be the cause in this schematic...

Best regards,
Gabriel Tudoran
Analog Sound

[WangoFett]

Measure the voltage at the output pin.  It should be 0V or very close to it (a few mV perhaps). 
If not, then this voltage could be caused by the capacitor used for C2, it may leaking too much current (a faulty capacitor or bad choice of capacitor type).
It could also be caused by a faulty connection on either side of R5 that would prevent it from doing it's job of holding the output side of C2 to ground.  Measure the resistance from the output pin to ground and it should read 100K.

If it even reads 10mV you will hear a click from the first true bypass switch that is connected to it, because that switch will be switching between (hopefully) 0V and 10mV, which will sound like a click / pop or thump.

[oliphaunt]

One pedal of mine had this issue, it turned out the bottom of the circuit board was touching ground somewhere.  There were no problems with components or the design, just in the way I mounted it.

[WangoFett]

Have you checked out the debugging thread?

Actually that won't help as much as searching for clicking and popping threads.