Fuzz Box HUMMMMMMM.....

[hohlamazoo]

I've been building on an entry level for about six months.  Of coarse, everything at this point has been fuzz or related.  I just finished a Bazz Fuss using a MPSA13 darlington and non-standard input and output caps.  Other than that, it's completely stock. 

The problem I'm having is a loud, low pitched hum when I set the pedal on the floor (basement).  It seems to be OK when it's on the table in front of me.  Also, when I touch the switch or the cable ends it gets significantly louder.  To further my experiment, I turned the volume down on the guitar and it doesn't go away.  If I remove the battery from the pedal, but still run through it, It's fine when bypassed, but creates hum when engaged.  Anyone have any suggestions? 

Oh, I also put a tiny cap from the output to ground.  It did improve slightly.  Thanks.

[theundeadelvis]

Have you double checked to be sure everything is properly grounded? A bad ground can definitely cause a pedal to hum. Maybe post a picture of the guts if you get a chance.

[hohlamazoo]

My wife has the camera, so that might prove difficult.  I did check all the the grounds by putting a multimeter on the battery + and then using the negative side to check the voltage at each ground connection.  I got the same reading everywhere.  I wondered why moving the pedal changed the hum?  I even tried different cables to make sure that wasn't the type of rookie mistake I was making.

[familyortiz]

+1 on a ground mis/disconnection.

[hohlamazoo]

I'll recheck everything tonight.  Thanks!

[hohlamazoo]

Oh, I forgot it's in a plastic uninsulated enclosure.  Is that a problem?

[theundeadelvis]

I can think of 2 issues a plastic enclosure may present.
1 - Plastic will not shield the circuit from outside noise/interference.
2 - Most offboard wiring diagrams show no connection made form the output jack to your ground point (usually the input jack sleeve). This is because the connection is made through the enclosure itself. However, if you are using a plastic box, this connection is not made, so you would need to run a wire from your output jack sleeve to your grounding point (input jack sleeve).

[hohlamazoo]

Yeah, I already had a ground running from the input sleeve to the output sleeve, then to ground.  So, what you're saying about interference might be the the problem.  I also retested all ground points with the positive for voltage and they were all consistently 9.6 volts.  Maybe I'm wrong, but it seems like they all have a good connection.  Thanks

[theundeadelvis]

Try lining the box with foil (or paint with conductive paint), and see if this helps.

[twabelljr]

Here is a short article on magnetic paint:
http://www.muzique.com/lab/magpaint.htm

[hohlamazoo]

Sorry, I just got back to see all of the helpful replies.  I think i'll give the foil tape or magnetic paint a try.  I noticed the hum is completely gone when I set the pedal on my laptop and desktop computer tower.  It really makes me scratch my head and wonder what the computers have inside that is helping.  Thanks again.