Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Guitar hum issue

Status
Not open for further replies.

Jack.Straw

Member
Hello. I'm building an Ashbory-type bass guitar. I'm using the ashbory preamp with the addition of an on/off switch. I also detached the LED from the circuit board. On testing the installation i'm getting a hum when the volume is not on full. On full volume everything is fine. Anything below that creates a hum. The hum is removed when touching any of the controls. I think I have everything grounded well, but i'm new at this. Anyone understand such things that can point me in the right direction?

Here is the schematic and close-up pictures of the preamp front & back:
Ashbory Bass Schematic

Here is a picture of my installation. I used shielded wire everywhere.
**broken link removed**

Thanks for any advice you can offer!
-Scott
 

mneary

New Member
You probably need to put shield between the sensitive electronics and you. Try a piece of aluminum foil lining the cavity where the amplifier sits. You can insulate the foil by covering it with masking tape or similar.

You could first try grounding the strings, assuming they are metal.
 

Jack.Straw

Member
mneary, thanks for the reply. They are not metal strings... they are some sort of poly i think. I have copper shielding tape i could wrap the preamp in, if it's really needed. Does it mean something that the hum isn't there when the volume is on "10" or 0?
 

Jack.Straw

Member
audioguru, thanks! Unfortunately I'm not sure what you mean by that. Solder a wire from the cases of the pots to... the ground? Where do i get 0v?

Thanks again for all your help... my charger is working great!
 

mneary

New Member
Now there's no hum at 0. We're making progress. What did you do?

Anyhow, connect the cases of the controls to 'ground' as well as making a shield around what you can, also connected to ground.

You get ground from the shield connection of almost any wire.
 

audioguru

Well-Known Member
Most Helpful Member
You probably cannot solder to the cases. The heat might destroy the pots.
Bolt terminals on the pots and solder wires from the terminals to 0V.

I didn't say "ground' because I didn't want you to run a 2km wire down the street to an earth ground. In this circuit 0V is ground.
 

Jack.Straw

Member
Awesome, thanks guys! I did solder to the cases (ooops... acted too fast), so hopefully i didn't hurt the pots too much. I just tested and the hum is gone! Thanks again for your help and time guys!!!
 
Hi,

I would still line the cavity with foil and have the cover, if not metal, lined with foil. Wait until you are on stage you will pick up other funnies.

Andrew
 

Ross Craney

New Member
How do your pickups work with non metalic strings ?
 
Status
Not open for further replies.

New Articles From Microcontroller Tips

Top