Fuzz Pedals Add Hum When Off

[alivegy]

I recently went through my pedal board on a quest to find pedals that were causing excess noise. I run a strat through a cranked jcm800 so any noise early in the chain becomes really prominent. I noticed that my two hartman pedals, an 8va octafuzz clone and a rangemaster treblebooster both inject a low hum into my signal when the pedals are DISENGAGED. The hartman pedals run on batteries, so they dont share a power supply with all of my other pedals that run on a pedal power 2. Any ideas what could cause this?

 

[Glitch Magnet]

Are they true bypass?

It may not be the pedals, but the wiring. Try repositioning the cables to see if there's a change.

Is there a power supply near these pedals? Most power supplies emit EMI that can get induced into the cabling and amplified downstream.

Even using batteries, you can get a ground loop if there's any metal-to-metal contact between pedals or the connected cabling.

Verify the pedal enclosures are properly grounded. If the hum gets louder when touching the pedal or footswitch, it's probably not.