Hum with electric guitar and bass in Breadboard JFET (single gain stage)

[777funk]

I'm getting some great sounding tones out of a basic JFET gain stage (similar wiring to a 12ax7 common cathode Fender type setup) similar to the Till Preamp. When I roll the volume down on an electric guitar or bass, it goes away but with the volume up, it's unusable.

Where do I look? One thing I noticed is that in the Till amp the input from the shielded cable goes direct to the FET gate. I put a 56k resistor in series (like you'd see in a Fender amp) and this helped. Anything else I can do?

I have basically a star ground on the breadboard (all grounds in one series of holes).

The hum goes away with the guitar volume down (shorting the input) and the power supply is a 9V battery.

 

[radardoug]

Is it in a shielded box? Are you sure its not the guitar producing the hum? Are you using Acme super handmade virgins hair cables?

 

[777funk]

SOLVED: I put the circuit inside an enclosure and everything is good now.

I built it on a breadboard and a perfboard and both examples were very noisy with interference. I put it in an Altoids tin and quiet as a mouse.

 

[alexc]

Enjoy the silence

Well done.

It still amazes me what a 9V and a few transistors can do for and to, a guitar or bass.

Hum absolutely kills me, so I use active and noise reducing pickups where possible.
It's incredible how quiet emg pups are compared to stock.

But yes, a nice enclosure can make a big difference.