Buzzing in preamp circuit?

[JGAN]

Hey guys,
I finally finished my tillman preamp circuit I will be posting more on it later, but it seems to be helping the tone quality already. However, I do have a problem with buzzing/humming from the circuit. It happens whenever plugged in and switched on, and I don't think its the battery. The buzzing does go away when I short the input though. Could I have bad jacks?

Thanks,
JGAN

[Osvaldo de Banfield]

... or improperly wired or shielded.

[JGAN]

I don't think I did anything wrong when soldering, but how do I go about shielding?

[Osvaldo de Banfield]

Which is the input impedance of such stuff?

[JGAN]

Discrete FET Guitar Preamp

3.0M Ω input impedance.

[Osvaldo de Banfield]

3Megohm is a very high input impedance. So a good shielding is imperative. Shield al conections from board to the input plug, and tie the shield to gnd of the circuit at only one point. Also, I suggest to add a source follower at the output of your circuit to come from low impedance to a cable then to the amp.

[JGAN]

I actually may have built the circuit wrong. For a n-channel JFET transistor, which is the correct schematic (drain vs source)?

Or...

[doozerdave]

You may be creating a ground loop with the input equipment. Have you been careful with power and signal grounding in your pre-amp to avoid power noise running along with signal ground?

[Osvaldo de Banfield]

No, most JFET have D & S interchangeable, ans in the particular case yours not, it will not work properly, but isn´t the cause to hum. Distortion may be, but not hum/noise.

[JGAN]

Originally Posted by doozerdave

You may be creating a ground loop with the input equipment. Have you been careful with power and signal grounding in your pre-amp to avoid power noise running along with signal ground?

I'm not exactly sure what that means?