I want to use a piezo transducer to make a contact pickup for my guitar. I am using a schematic found from Make Magazine to create a little preamp. Also, I want to install a potentiometer to control the volume of the pickup. Quite frankly, Im not sure what resistance pot I should buy and where to wire it. Im sure this is a very straightforward question, but I just don't know enough about electronics to confidently put it it. Ive attached a diagram of the schematic for the preamp. All the components are marked on the schematic. Thanks for the help!

 

Put a 1 megohm audio taper potentiometer where the 3.3M resistor is. Connect the input of the jfet to the wiper of the pot. Throw the 3.3M resistor in your parts box.

If that doesn't work because your piezo wants a really high resistance. you will have to place a 250k volume control in the 220K position and use the wiper for the output lead.

 

yep i would use the 220K as a volume control with the wiper to the output ...

 

Put a 1 megohm audio taper potentiometer where the 3.3M resistor is. Connect the input of the jfet to the wiper of the pot. Throw the 3.3M resistor in your parts box.

If that doesn't work because your piezo wants a really high resistance. you will have to place a 250k volume control in the 220K position and use the wiper for the output lead.

Thanks #12, I'll try that out!

 

yep i would use the 220K as a volume control with the wiper to the output ...


View attachment 89816

Thanks for the schematic!