Biasing Jfets by ear - noisy trimmers

[MAO]

I just recently started to bias jfets by ear and noticed some noise while adjusting two of the trimmers. A Plexi Drive and ROG Ginger.

I've never had the amp on before while biasing jfets, it just so happens on the 1st two build I tried this technique I noticed the noise. The pedals sound fine otherwise. So I'm not sure if this noise while adjusting is "normal".  

Seems strange as the noise only happens with one of the trimmers on each build. I'm using the cheap Tayda 6mm trimmers.

My troubleshooting plan is as follows:

1. re-flow all solder joints around the offending trimmers.
2. Swap out the offending trimmer(s)
3. Swap out the jfet (socketed, but have to make some more smd adapter boards)
4. Swap out caps around the trimmer.

I'm hoping to tap into all of the experience out there and save some time de-soldering and troubleshooting.

As always, thanks.  
Mike

[strewel_peterson]

Depends where the trimmer is in the circuit, of course, but if there's DC present you may well get noise when adjusting it. Crackle OK, as it says on the SHO boxes!

[induction]

It's normal for jfets to produce noise while rebiasing.

[MAO]

Thanks guys, I'm sure you just saved me a whole lot of time and frustration.

Appreciate it.